Avaerage Age Of Dating Begins In Usa

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Obstet Gynecol Clin North Am. Author manuscript; available in PMC 2012 Sep 1.

Dating customs have changed since you were a teenager. The most striking difference is the young age at which children now begin dating: on average, twelve and a half for girls, and thirteen and a half for boys. However, you might not recognize it as dating per se. The recent trend among early adolescents is for boys and girls to. A massive new study of online dating finds that everyone dates aspirationally—and that a woman’s desirability peaks 32 years before a man’s does.

Published in final edited form as:
doi: 10.1016/j.ogc.2011.05.002
NIHMSID: NIHMS353085
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The age at the final menstrual period holds intrinsic clinical and public health interest because the age at which natural menopause occurs may be a marker of aging and health. Later age at natural menopause has been associated with:

  • longer overall survival and greater life expectancy and reduced all-cause mortality;

  • reduced risk of cardiovascular disease,– and mortality from cardiovascular and ischemic heart disease, stroke, angina after myocardial infarction, and atherosclerosis;

  • less loss of bone density, and a reduced risk of osteoporosis and fracture;

  • but an increased risk of breast,, endometrial, and ovarian,– cancers.

In addition, women who have undergone bilateral oophorectomy under the age of 45 years have been observed to be at increased risk of mortality from cardiovascular disease, particularly if they were not treated with estrogen. However, women who underwent natural menopause before age 45 years had an increased risk of ischemic heart disease that was not attenuated by use of hormone therapy. Further, early menopause has been associated with earlier decline in cognitive function. Because 40 million women in the United States alone and several hundred million worldwide31 experienced the menopausal transition between 1990 and 2010 due to the aging of the baby boomer generation, millions of women are undergoing or have recently undergone the menopause transition, and the timing of their final natural menstrual periods could have important clinical and health implications, because one third of women's lives is spent postmenopause.

Although menopause is a universal phenomenon among women, the timing of the onset and the duration of the menopausal transition and the timing of the final menstrual period are not. Most of our knowledge and perceptions of menopause have been based largely on studies of white women, and many have been studies of clinic-based, rather than population-based, samples of women. Thus, until recently, much of the knowledge about the timing of the natural final menstrual period has been affected by the nature of the samples of women studied and a number of other methodologic differences in the studies of this phenomenon, which must be considered in comparing and summarizing their results.

METHODOLOGIC CONCERNS

Most studies of the menopausal transition have been cross-sectional, rather than longitudinal, in design, providing an opportunity for distortion of the true picture of the timing of the final natural menstrual period, particularly for understanding factors that precede and may affect the timing of menopause. Further, definitions of menopause or the final menstrual period have varied from study to study in terms of the number of months of amenorrhea considered to represent in retrospect the final menstrual period. Studies have also varied with regard to which factors have been included in multivariable analyses that control simultaneously for the effects of multiple variables, which also makes the studies not directly comparable.

The analysis of age at natural menopause in a number of studies has been calculated as a simple mean, rather than using the less-biased survival or multivariable time-to-event analytic approaches. These last two approaches include more information and observations for every woman studied, because all women are included but withdrawn or censored when they experience surgical menopause, start using menopausal hormone therapy or oral contraceptives (OC; which generally masks the natural cessation of menses), or are still premenopausal. Also, the accuracy of reporting of age at menopause can vary by whether menopause was natural and by duration from the time of the final menstrual period to the time of the interview about menopause, the latter being directly affected by the age group of the study sample. Further, in some studies that have reported age at menopause, it is unclear if the age at the final menstrual period is being reported, the more frequent approach, or if the age at cessation of menses plus 1 year of amenorrhea, the World Health Organization's definition of menopause.31 is what is reported, a more rare occurrence. Most studies do not use a hormonally based definition of menopause.

Recently, more information has been published regarding differences in the timing of menopause experienced by samples of women of different socioeconomic, racial/ethnic, and lifestyle backgrounds, and standardization of instruments and definitions has increased, resulting in a fuller, clearer, and more insightful picture regarding the underlying physiology.

SUMMARY OF UNDERLYING PHYSIOLOGY

Menopause is defined as the cessation of menstruation which reflects cessation of ovulation owing to a loss of ovarian follicles, which in turn results in reduced ovarian production of estradiol, the most biologically active form of estrogen,37, as well as increased circulating concentrations of follicle-stimulating hormone (FSH) and decreased concentrations of inhibin, which inhibits the release of FSH.37 Age at menopause may be more sensitive to varying rates of atresia of ovarian follicles than to the absolute number of oocytes depleted, but menopause is reached when depletion of follicles reaches approximately 1000 (from a peak of 5 million follicles at mid-gestation and 2 million at birth)., The age at which sufficient depletion of follicles occurs is affected by the number of follicles achieving migration to the gonadal ridge during gestation, their mitotic abilities until mid-gestation, and the rate of follicular atresia.,

As circulating estrogen concentrations decline during the menopausal transition, variations in the regularity, timing, and nature of menstrual bleeding may occur. As menstrual cycles become increasingly irregular, bleeding may occur after an inadequate luteal phase or without ovulation, usually indicated by a short luteal phase, characteristic of women over the age of 40 years., Such cycles may be associated with insufficient FSH (or insufficient FSH responsiveness of the follicle) in the follicular phase, in turn resulting in lower luteal phase estrogen and progesterone secretion. Lack of a corpus luteum, resulting in estrogen secretion (even hyperestrogenicity,) unopposed by progesterone, may lead to profuse bleeding.

The nature and timing of bleeding may vary both within and between women. What is known about the host, environmental, or lifestyle factors that may affect such variation is summarized herein. Although some factors have been identified that are associated with early age at natural menopause, the relation of many has not been examined, and most have not been examined in relation to duration of the perimenopause.

Factors Related to Timing of Menopause

Results from cross-sectional studies have indicated that endocrine changes characteristic of the onset of the perimenopause begin at around age 45. The median age at menopause among white women from industrialized countries ranges between 50 and 52 years and at onset of the perimenopause is 47.5 years, with slight evidence of increasing age at menopause over time. These onsets seem to vary by race and ethnicity and are affected by demographic and lifestyle factors.50,– Although some studies have reported no familial relationship, 1 study has reported that age at menopause was positively associated with maternal age at menopause, and 1 recent study has shown genetic control of age at menopause in a study of twins. However, a number of potentially modifiable factors which may affect estrogen metabolism, including body mass index (BMI), diet (particularly calories and alcohol intake), and passive smoke exposure have not been examined, nor has the time-varying effect of these and of the other factors that have been previously identified been examined in longitudinal analyses of sufficiently large and diverse study populations.

Sociodemographic Differences

International and geographic differences

Several studies have indicated that women living in developing countries (including Latin America, Indonesia, Singapore, Pakistan, Chile, and Peru) experience natural menopause several years earlier than those in developed countries. Some work has also indicated that women living in urban areas have a later natural menopause than women in rural areas. Women living at high altitude in the Himalayas or in the Andes of Peru undergo natural menopause 1 to 1.5 years earlier than those living at lower altitudes or in less rural areas.72,–79 It is unclear whether these geographic and international differences in the age at natural menopause reflect genetic, socioeconomic, environmental, racial/ethnic, or lifestyle differences and whether and how these affect physiology.

Racial/ethnic differences

Some studies have reported that African American and Latina, women have natural menopause about 2 years earlier than white women. However, 1 small study in Nigeria reported the average age at menopause to be 52.8 years, over 1 year later than that generally reported for white women in industrialized nations. Mayan women, despite their high parity (see Reproductive History), have been reported to experience natural menopause fairly early, at about age 45. In contrast, Asian women tend to have similar age at menopause to Caucasian women,,82 although Thai women have been reported to have a lower median age at menopause, at age 49.5 years, despite their high parity, and Filipino Malay women have been reported to have an earlier average age at natural menopause at 47 to 48 years.

Differences by socioeconomic status

A number of studies have observed that lower social class, as measured by the woman's educational attainment or by her own or her husband's occupation, is associated with an earlier age at natural menopause.–, However, results from a British birth cohort indicated that early life socioeconomic status (SES) was more strongly associated than adult status with age at natural menopause, although even the relation of early life SES was greatly attenuated when adjusted for childhood cognitive ability and having been breastfed. One study found that education was more strongly associated with age at natural menopause than occupation. Most studies that have examined the relation of marital status have found that single women undergo an earlier natural menopause, and this association cannot be explained by nulliparity.,

Health-Related Influences

Menstrual and reproductive history

The age at which the final natural menstrual period occurs may be a marker for hormonal status or changes earlier in life. In the landmark Treloar longitudinal study of largely white, well-educated women, those whose median menstrual cycle length between the ages of 20 and 35 years was fewer than 26 days underwent natural menopause 1.4 years earlier than women with cycle lengths between 26 and 32 days, whereas a later natural menopause (mean = 0.8 year later) was observed in women with cycle lengths of 33 days or longer. In addition, 9 or more days of variability in cycle length has been associated with a later age at natural menopause in this and other studies,, although 1 study reported an earlier natural menopause in women with irregular menses.

Increasing parity, particularly among women of higher SES, has also been associated with later age at natural menopause,50–,– consistent with the theory that natural menopause occurs after oocytes have been sufficiently depleted. Although some studies have reported no familial relationship, 1 study reported that women's age at natural menopause was positively associated with their mother's age at natural menopause, and 1 study of twins showed genetic control of age at natural menopause. Age at menarche has been fairly consistently observed not to be associated with age at menopause, after adjusting for parity and cycle length,, as have prior spontaneous abortion, age at first birth, and history of breastfeeding.,

A number of studies have reported that women who have used OCs have a later age at natural menopause.,72, an observation that is also consistent with the theory that OCs delay depletion of oocytes. However, the finding has not been wholly consistent across studies, because 1 study reported that this delay became nonsignificant after a time-dependent adjustment for when OCs were used, and another study reported that OC users had a significantly earlier natural menopause than nonusers, although this association was not consistent across 5-year age groups.50

Body mass and composition

Several studies have examined the relation of body mass to age at menopause, with inconsistent findings. Some studies have reported that both increased BMI (indicated by weight over height squared) and upper body fat distribution (indicated by waist-to-hip ratio) were associated with later age at natural menopause50, and increased sex hormone concentrations. However, at least as many other studies have reported no significant association of BMI with age at natural menopause., Some studies have found a relationship between lower weight or increased upper body fat distribution and earlier age at natural menopause, particularly among smokers. One study reported earlier natural menopause in women on weight reduction programs or who had gained more than 26 pounds between the ages of 20 and 45 years.

Some of these apparently inconsistent findings may be explained by differences in study design (cross-sectional or retrospective vs prospective) or analysis (eg, inadequate or varying control of confounding variables or survival analysis vs. comparison of crude means). In general, the better designed and analyzed studies have shown no relation of body mass or body fat distribution to age at the final natural menstrual period. Although body mass and composition may be related to age at natural menopause, they are also related inversely to physical activity, alcohol consumption, and education, and positively related to infertility and parity. Further research is needed in which all of these potentially confounding variables are simultaneously controlled in the statistical analyses of data from large study samples to be able to assess adequately the independent contribution or interactive effect of body mass and composition and these other factors on the age at the natural final menstrual period and duration of menopause transition, using appropriate longitudinal study design and data analysis techniques.

Familial, genetic, and early childhood factors

In recent years, studies of factors related to age at natural menopause have begun to focus on genetic factors that may be related. Results of family and twin studies suggest that familial and genetic factors may play an important role, with estimates of heritability ranging from 30% to 85%., In 1 relatively large cross-sectional study and 1 large longitudinal British birth cohort study, a strong association was found between mothers' and daughters' ages at natural menopause,, which have also been found in a few other smaller studies, but few longitudinal studies have investigated this relationship. One European genome-wide association study of nearly 3000 women identified 6 single nucleotide polymorphisms in 3 loci on chromosomes 13, 19, and 20 associated with age at natural menopause. A Dutch study showed that polymorphisms of an estrogen receptor gene were associated with earlier natural and surgical menopause. Results of genome-wide association studies, using samples from thousands of women in the Nurses' Health Study and the Women's Genome Health Study, identified 13 single nucleotide polymorphisms on 4 chromosomes that were associated with age at menopause. Analyses of candidate genes from 9 biologically plausible pathways, using the same samples from the same women in these 2 studies, indicated that the steroid hormone metabolism and biosynthesis pathways were associated with age at natural menopause and that genes involved in premature ovarian failure were also significantly associated with age at menopause. Two single nucleotide polymorphisms of the tumor necrosis factor receptor family have also been shown to be significantly associated with age at natural menopause.

A number of analyses have been conducted on prospective data collected across the lifespan from a nationally representative birth cohort of nearly 1600 British women born in 1946 and followed to age 53 years, the Medical Research Council National Survey of Health and Development. These analyses have revealed that women who had a low weight at 2 years of age had an earlier natural menopause, whereas those who were heaviest at 2 years of age had a later natural menopause. Those who were breastfed had a later natural menopause. Another cohort study in England also found that low weight at 1 year of age was associated with earlier natural menopause. However, an Australian twin study and the English cohort study found no association of birth weight with age at natural menopause., The British birth cohort and other cohort studies have shown that poorer cognitive ability in childhood was associated with earlier natural menopause, suggesting that perhaps markers in early life may determine not only age at natural menopause, but may also predict the adverse health outcomes that are associated with early age at menopause. Further, additional findings from the British birth cohort indicate that women whose parents divorced early in their lives had an earlier natural menopause than other women, suggesting that early life stressors may also be related to early menopause.,

Environmental Influences

Active and passive smoke exposure

Perhaps the single most consistently shown environmental effect on age at menopause is that women who smoke stop menstruating 1 to 2 years earlier than comparable nonsmokers.50,–,–, and have a shorter perimenopause. Some studies have shown a dose–response effect on atrophy of ovarian follicles, in that heavy smokers have an earlier natural menopause than light smokers., Former smokers have only a slightly earlier age at natural menopause than those who never smoked, and increased time since quitting diminishes the difference.,125 The latter observation of only a slightly earlier natural menopause in former smokers is inconsistent with the presumed toxic effect of smoking on ovarian follicles, resulting in their atrophy and thus earlier menopause, because such an effect should be nonreversible so that former smokers would also experience the earlier natural menopause observed in current smokers. If the dose–response effect is a true effect, the apparent paradox might partly be explained by fewer years of smoking and thus toxic exposure to the ovaries in former smokers than in current smokers of similar age.

The polycyclic aromatic hydrocarbons in cigarette smoke are known to be toxic to ovarian follicles, and thus could result in premature loss of ovarian follicles and early natural menopause among smokers. Because drug metabolism is enhanced in smokers, estrogen also may be more rapidly metabolized in the livers of smokers, which could lead to an earlier reduction of estrogen levels. Further, smoking has also been observed to have antiestrogenic effects. Greater prevalence of hysterectomy among premenopausal smokers than nonsmokers, apparently does not account for smokers having an earlier natural menopause. Only 1 study has shown that nonsmoking women whose spouses smoked had an age at natural menopause resembling that of smokers; thus, very little is known about the effect of passive or secondhand smoke exposure on the age at which the final natural menstrual period is experienced.

Occupational/environmental factors

Although almost nothing is known about the relations of occupational or other environmental factors to age at the final natural menstrual period and duration of the menopausal transition, occupational exposures and stressors (such as shift work, hours worked, hours spent standing, and heavy lifting) have been related to increased risk of adverse pregnancy outcomes and changes in menstrual cycle length and variability as well as fecundability. In addition, such environmental exposures as dichlorodiphenyltrichloroethane and polychlorinated biphenyls have been shown to have estrogenic activity and to be associated with an increased risk of breast cancer,, although this association has not been consistently observed., Thus, the presumed endocrine effects of such exposures make it reasonable to expect that occupational and environmental exposures may be related to endocrine disruption that is reflected in altered age at natural menopause. One study showed a modest effect on age at natural menopause in women in Seveso, Italy, who were exposed to 2,3,7,8-tetrachlorobenzo-p-dioxin, a halogenated compound that may affect ovarian function, during a chemical plant explosion in 1976. Another study showed that exposure to 1,1-dichloro-2,2-bis(p-chlorophenyl) ethylene was also associated with earlier natural menopause.

Physical activity

Physical activity is associated with a number of changes in hormonal parameters [estradiol, progesterone, prolactin, luteinizing hormone (LH), and FSH), both during and after intense physical activity. The concentrations of these hormones tend to be lower at rest among women who are physically active., Also, athletes tend to have a later age at menarche and increased occurrences of anovulation and amenorrhea and, among those who menstruate, a shortened luteal phase and reduced mean and peak progesterone levels., Although physical activity is associated with decreased concentrations of reproductive hormones and frequency of ovulation, few studies have examined the effect of exercise on age at natural menopause, although 1 modestly sized study reported no relationship, and 1 large study of Chinese women showed a later age at natural menopause associated with leisure time physical activity during adolescence and adulthood.

Diet

One early study from Papua, New Guinea, suggested that malnourished women ceased menstruation about 4 years earlier than well-nourished women,153 consistent with other studies showing that women with greater weight, and height may have a later age at natural menopause. Findings regarding the relationship of specific dietary patterns to age at menopause have been inconsistent. For example, vegetarians were observed to have an earlier age at natural menopause in 1 study,154 whereas another study in Japan reported that higher green and yellow vegetable intake was significantly associated with later age at natural menopause. Further, a large cross-sectional study of Japanese women found that higher intakes of fat, cholesterol, and coffee were significantly associated with earlier natural menopause after controlling for age, total energy, parity, menarche age, and relative weight. A longitudinal study of nearly 5000 German women observed that high carbohydrate consumption and high intake of vegetable, fiber, and cereal products were related to an earlier age at natural menopause, whereas higher intake of total fat, protein, and meat were associated with a later natural menopause. The large, prospective Shanghai Women's Health Study found that higher total intake of calories, fruits, and protein was significantly associated with later age at natural menopause, whereas vegetable, fat, soy, and fiber intakes were not significantly related to age at menopause. Inclusion of meat in the diet of vegetarians has been observed to increase the episodic releases of LH and FSH and the length of the menstrual cycle. Thus, meat may modify the interaction of hormones along the hypothalamic-pituitary-ovarian axis. A couple of studies have reported that increased meat or alcohol consumption is significantly associated with later age at menopause, after adjusting for age and smoking., Dietary fiber (whose intake tends to be inversely related to meat intake) may interrupt enterohepatic circulation of sex hormones, leading to the lower circulating estrogen concentrations among vegetarian women.159 Nonetheless, a low-fat, high-carbohydrate intervention diet to prevent breast cancer in over 2600 women with extensive mammographic density followed for an average 7 years did not influence the timing of natural menopause, except a significantly earlier natural menopause was observed in those with low BMI who were on the intervention diet.

Premenopausal women administered soy have shown increased plasma estradiol concentrations and follicular phase length, delayed menstruation, and suppressed midcycle surges of LH and FSH. Among postmenopausal women fed soy, FSH and LH did not decrease significantly, nor did sex hormone-binding globulin increase, and little change occurred in endogenous estradiol or body weight, although a small estrogenic effect on vaginal cytology was observed. However, the role of dietary fiber, phytoestrogens, fat, protein, and other nutrients in affecting age at menopause and duration of the perimenopause remains to be systematically studied, but has potentially important implications for prevention of chronic disease in midlife and older women.

CONCLUSION

Despite important methodologic differences, the limitations in the study designs used and the populations studied in the accumulating literature regarding factors that affect the age at which the natural final menstrual period is experienced, an interesting and complex picture is emerging. A number of demographic (eg, education, employment, race/ethnicity), menstrual and reproductive (eg, parity and OC use), familial and genetic, and lifestyle (eg, smoking, weight, physical activity and diet) factors seem to be important determinants of the age at which natural menopause occurs. Smoking, lower parity, and lower SES have been found fairly consistently to be associated with earlier menopause, an indicator of reduced longevity. However, the relationships with African American and Latina race/ethnicity, vegetarian diet, and undernutrition, body mass and composition, and physical activity have been inconsistent, possibly owing to varying methodologic approaches and limitations (Table 1).

Table 1

Factors related to earlier and later age at natural menopause

Factors Consistently Related to Earlier Age at Natural Menopause (References)Factors Inconsistently Related to Age at Natural Menopause (References)
Low socioeconomic status51–54,57,58,61,71,85–88Race/ethnicity58–60,80–84
Low/parity50–52,55,57,58,61,90,91,93,96Body mass index or body com position50–52,54,57,59,62,69,98–101
Not using oral contraceptives50,52,58,61,63,72,98Physical activity59,94
Active smoking50,51,55,57–59,61,63–69,86,96,121,124–126Dietary (vegetable, meat, fat, fiber) intake61,121,153–157,160

Other relationships remain largely unexplored (eg, passive smoke exposure and occupational and other environmental exposures). Therefore, much remains to be learned about how these factors affect follicular atresia and hormone levels and thus determine the onset and potentially the duration of the perimenopause and the timing of the final menstrual period. Furthermore, increased understanding of the underlying physiologic mechanisms of these influences needs to include potential genetic, metabolic, and racial/ethnic differences in physiologic responses to lifestyle factors and other environmental exposures and the interaction of genetic factors with these lifestyle and environmental factors. Increasing knowledge about these relationships ultimately offers women and their health care providers enhanced understanding and choices, based on greater knowledge, to deal with the individual presentations of menopause.

ACKNOWLEDGMENTS

The Study of Women's Health Across the Nation (SWAN) has grant support from the National Institutes of Health (NIH), DHHS, through the National Institute on Aging (NIA), the National Institute of Nursing Research (NINR) and the NIH Office of Research on Women's Health (ORWH) (Grants NR004061; AG012505, AG012535, AG012531, AG012539, AG012546, AG012553, AG012554, AG012495). Dr Gold was supported by AG012554. The content of this article is solely the responsibility of the author and does not necessarily represent the official views of the NIA, NINR, ORWH or the NIH.

REFERENCES

Avaerage Age Of Dating Begins In Usa
1. Cooper GS, Sandler DP. Age at natural menopause and mortality. Ann Epidemiol. 1998;8:229–35. [PubMed] [Google Scholar]
2. Wise AM, Krajnak KM, Kashon ML. Menopause: the aging of multiple pacemakers. Science. 1996;273:67–70. [PubMed] [Google Scholar]
3. Snowdon DA, Kane RL, Beeson WL, et al. Is early natural menopause a biologic marker of health and aging? Am J Public Health. 1989;79:709–14.[PMC free article] [PubMed] [Google Scholar]
4. Ossewaarde ME, Bots ML, Verbeek ALM, et al. Age at menopause, cause-specific mortality and total life expectancy. Epidemiology. 2005;16:556–62. [PubMed] [Google Scholar]
5. Jacobsen BK, Heuch I, Kvale G. Age at natural menopause and all-cause mortality: a 37-year follow-up of 19,731 Norwegian women. Am J Epidemiol. 2003;157:923–9. [PubMed] [Google Scholar]
6. De Kleijn MJ, van der Schouw YT, Verbeek AL, et al. Endogenous estrogen exposure and cardiovascular mortality risk in postmenopausal women. Am J Epidemiol. 2002;155:339–45. [PubMed] [Google Scholar]
7. Van der Schouw YT, van der Graaf Y, Steyerberg EW, et al. Age at menopause as a risk factor for cardiovascular mortality. Lancet. 1996;347:714–8. [PubMed] [Google Scholar]
8. Jacobsen BK, Nilssen S, Heuch I, et al. Does age at natural menopause affect mortality from ischemic heart disease? J Clin Epidemiol. 1997;50:475–9. [PubMed] [Google Scholar]
9. Hu FB, Grodstein F, Hennekens CH, et al. Age at natural menopause and risk of cardiovascular disease. Arch Intern Med. 1999;159:1061–6. [PubMed] [Google Scholar]
10. Atsma F, Bartelink ML, Grobbec DE, et al. Postmenopausal status and early menopause as independent risk factors for cardiovascular disease: a meta-analysis. Menopause. 2006;13:265–79. [PubMed] [Google Scholar]
11. Cui R, Iso H, Toyoshima H, et al. JACC Study Group. Relationships of age at menarche and menopause, and reproductive year with mortality from cardiovascular disease in Japanese postmenopausal women: the JACC study. J Epidemiol. 2006;16:177–84.[PMC free article] [PubMed] [Google Scholar]
12. Jansen SC, Temme EH, Schouten EG. Lifetime estrogen exposure versus age at menopause as mortality predictor. Maturitas. 2002;43:105–12. [PubMed] [Google Scholar]
13. Jacobsen BK, Knutsen SF, Fraser GE. Age at natural menopause and total mortality and mortality from ischemic heart disease: the Adventist Health Study. J Clin Epidemiol. 1999;52:303–7. [PubMed] [Google Scholar]
14. Lisabeth LD, Beiser AS, Brown DL, et al. Age at natural menopause and risk of ischemic stroke The Framingham Heart Study. Stroke. 2009;40:1044–9.[PMC free article] [PubMed] [Google Scholar]
15. Parashar S, Reid KJ, Spertus JA, et al. Early menopause predicts angina after myocardial infarction. Menopause. 2010;17:938–45.[PMC free article] [PubMed] [Google Scholar]
16. Joakimsen O, Bonaa KH, Stensland-Bugge E, et al. Population-based study of age at menopause and ultrasound assessed carotid atherosclerosis: the Tromso Study. J Clin Epidemiol. 2000;53:525–30. [PubMed] [Google Scholar]
17. Parazzini F, Bidoli E, Franceschi S, et al. Menopause, menstrual and reproductive history, and bone density in northern Italy. J Epidemiol Community Health. 1996;50:519–23.[PMC free article] [PubMed] [Google Scholar]
18. Kritz-Silverstein D, Barrett-Connor E. Early menopause, number of reproductive years, and bone mineral density in postmenopausal women. Am J Public Health. 1993;83:983–8.[PMC free article] [PubMed] [Google Scholar]
19. Van Der Voort DJ, Van Der Weijer PH, Barentsen R. Early menopause: increased fracture risk at older age. Osteoporos Int. 2003;14:525–30. [PubMed] [Google Scholar]
20. Kelsey JL, Gammon MD, John EM. Reproductive factors and breast cancer. Epidemiol Rev. 1993;15:36–47. [PubMed] [Google Scholar]
21. Monninkhof EM, van der Schouw YT, Peeters PH. Early age at menopause and breast cancer: are leaner women more protected? A prospective analysis of the Dutch DOM cohort. Breast Cancer Res Treat. 1999;55:285–91. [PubMed] [Google Scholar]
22. De Graaff J, Stolte LA. Age at menarche and menopause of uterine cancer patients. Eur J Obstet Gynecol Reprod Biol. 1978;8:187–93. [PubMed] [Google Scholar]
23. Franceschi S, La Vecchia C, Booth M, et al. Pooled analysis of 3 European case-control studies of ovarian cancer: II. Age at menarche and at menopause. Int J Cancer. 1991;49:57–61. [PubMed] [Google Scholar]
24. Kaaks R, Lukanova A, Kurzer MS. Obesity, endogenous hormones, and endometrial cancer risk: a synthetic review. Cancer Epidemiol Biomarkers Prev. 2002;11:1531–43. [PubMed] [Google Scholar]
25. Xu WH, Xiang YB, Ruan ZX, et al. Menstrual and reproductive factors and endometrial cancer risk: results from a population-based case-control study in urban Shanghai. Int J Cancer. 2004;108:613–9. [PubMed] [Google Scholar]
26. Rivera CM, Grossardt BR, Rhodes DJ, et al. Increased cardiovascular mortality after early bilateral oophorectomy. Menopause. 2009;16:15–23.[PMC free article] [PubMed] [Google Scholar]
27. Lokkegaard E, Jovanovic Z, Heitmann BL, et al. The association between early menopause and risk of ischaemic heart disease: influence of hormone therapy. Maturitas. 2006;53:226–33. [PubMed] [Google Scholar]
28. Woods NF, Mitchell ES, Adams C. Memory functioning among midlife women: observations for the Seattle Midlife Women's health Study. Menopause. 2000;7:257–65. [PubMed] [Google Scholar]
29. Halbreich U, Piletz J, Halaris A. Influence of gonadal hormones on neurotransmitters, receptor, cognition and mood. Clin Neuropharmacol. 1992;15(Suppl A):590A–1A. [PubMed] [Google Scholar]
30. Kok HS, Kuh D, Cooper R, et al. Cognitive function across the life course and the menopausal transition in a British birth cohort. Menopause. 2006;13:19–27. [PubMed] [Google Scholar]
31. World Health Organization . Research on the menopause in the 1990s. World Health Organization; Geneva (Switzerland): 1996. [Google Scholar]
32. Skolnick AA. At third meeting, menopause experts make the most of insufficient data. JAMA. 1992;268:2483–5. [PubMed] [Google Scholar]
33. Avis NE, Kaufert PA, Lock M, et al. The evolution of menopausal symptoms. Baillieres Clin Endocrinol Metab. 1993;7:17–32. [PubMed] [Google Scholar]
34. Cramer DW, Xu H. Predicting age at menopause. Maturitas. 1996;23:319–26. [PubMed] [Google Scholar]
35. Hahn RA, Eaker E, Rolka H. Reliability of reported age at menopause. Am J Epidemiol. 1997;146:771–5. [PubMed] [Google Scholar]
36. Sowers MF, LaPietra MT. Menopause: its epidemiology and potential association with chronic diseases. Epidemiol Rev. 1995;17:287–302. [PubMed] [Google Scholar]
37. Gosden RG. Biology of the menopause: the causes and consequences of ovarian ageing. Academic Press; London: 1985. [Google Scholar]
38. Burger HG, Dudley EC, Hopper JL. The endocrinology of the menopausal transition: a cross-sectional study of a population-based sample. J Clin Endocrinol Metab. 1995;80:3537–45. [PubMed] [Google Scholar]
39. Soule MR, Bremner WJ. The menopause and climacteric: endocrinologic basis and associated symptomatology. J Am Geriatrics Soc. 1982;30:547. [PubMed] [Google Scholar]
40. Thomford PJ, Jelovsek FR, Mattison DR. Effect of oocyte number and rate of atresia on the age of menopause. Repro Toxicol. 1987;1:41–51. [PubMed] [Google Scholar]
41. Faddy MJ, Gosden RG, Gougeon A, et al. Accelerated disappearance of ovarian follicles in mid-life: implications for forecasting menopause. Hum Reprod. 1992;7:1342–6. [PubMed] [Google Scholar]
42. Ginsberg J. What determines the age at the menopause. BMJ. 1991;302:1288–9.[PMC free article] [PubMed] [Google Scholar]
43. Aydos SE, Elhan AH, Tukun A. Is telomere length one of the determinants of reproductive life span? Arch Gynecol Obstet. 2005;2727:113–6. [PubMed] [Google Scholar]
44. Sherman BM, West JH, Korenman SG. The menopausal transition: analysis of LH, FSH, estradiol and progesterone concentrations during menstrual cycles of older women. J Clin Endocrinol Metab. 1976;42:629–36. [PubMed] [Google Scholar]
45. Santoro N, Rosenberg-Brown J, Adel T, et al. Characterization of reproductive hormonal dynamics in the perimenopause. J Clin Endocrinol Metab. 1996;81:1495–1501. [PubMed] [Google Scholar]
46. Upton GV. The perimenopause: physiologic correlates and clinical management. J Reprod Med. 1982;27:1–28. [PubMed] [Google Scholar]
47. Shideler SE, DeVane GW, Kalra PS, et al. Ovarian pituitary hormone interactions during the menopause. Maturitas. 1989;11:331–9. [PubMed] [Google Scholar]
Average age of dating begins in usa 2020Age
48. Trevoux R, DeBrux J, Castaneir M, et al. Endometrium and plasma hormone profile in the peri-menopause and post-menopause. Maturitas. 1986;8:309–26. [PubMed] [Google Scholar]
49. McKinlay SM, Brambilla DJ, Posner JG. The normal menopause transition. Maturitas. 1992;14:103–15. [PubMed] [Google Scholar]
50. Greendale G, Hogan P, Kritz-Silverstein D, et al. Age at menopause in women participating in the postmenopausal estrogen/progestins interventions (PEPI) trial: an example of bias introduced by selection criteria. Menopause. 1995;2:27–34. for the PEPI trial investigators. [Google Scholar]
51. Luoto R, Laprio J, Uutela A. Age at natural menopause and sociodemographic status in Finland. Am J Epidemiol. 1994;139:64–76. [PubMed] [Google Scholar]
52. Stanford JL, Hartge P, Brinton LA, et al. Factors influencing the age at natural menopause. J Chron Dis. 1987;40:995–1002. [PubMed] [Google Scholar]
53. Magursky V, Mesko M, Sokolik L. Age at the menopause and onset of the climacteric in women of Martin district, Czechoslovakia. Int J Fertil. 1975;20:17–23. [PubMed] [Google Scholar]
54. Gold EB, Sternfeld B, Brown C, et al. The relation of demographic and lifestyle variables to symptoms in a multi-racial/ethnic population of women aged 40-55 years. Am J Epidemiol. 2000;152:463–73. [PubMed] [Google Scholar]
55. van Noord PAH, Dubas JS, Dorland M, et al. Age at natural menopause in a population-based screening cohort: the role of menarche, fecundity, and lifestyle factors. Fertil Steril. 1997;68:95–102. [PubMed] [Google Scholar]
56. Flint M. Is there a secular trend in age of menopause. Maturitas. 1978;1:133–9. [PubMed] [Google Scholar]
57. Rodstrom K, Bengtsson C, Milsom I, et al. Evidence for a secular trend in menopausal age: a population study of women in Gothenburg. Menopause. 2003;10:538–43. [PubMed] [Google Scholar]
58. Gold EB, Bromberger J, Crawford S, et al. Factors associated with age at menopause in a multi-ethnic population of women. Am J Epidemiol. 2001;153:865–74. [PubMed] [Google Scholar]
59. Bromberger JT, Matthews KA, Kuller LH, et al. Prospective study of the determinants of age at menopause. Am J Epidemiol. 1997;145:124–33. [PubMed] [Google Scholar]
60. Alvarado G, Rivera R, Ruiz R, et al. Characteristicas del patron de sangrado menstrual en un grupo de mujeres normales de Durango. Ginecol Obstetr Mex. 1988;56:127–33. [PubMed] [Google Scholar]
61. Torgerson DJ, Avenell A, Russell IT, et al. Factors associated with onset of menopause in women aged 45-49. Maturitas. 1994;19:83–92. [PubMed] [Google Scholar]
62. MacMahon B, Worcester J. Age at menopause, United States 1960-1962. Vital Health Stat. 1966;19:1–19. [PubMed] [Google Scholar]
63. Palmer JR, Rosenberg L, Wise LA, et al. Onset of natural menopause in African American women. Am J Public Health. 2003;93:299–306.[PMC free article] [PubMed] [Google Scholar]
64. McKinlay SM, Bifano NL, McKinlay JB. Smoking and age at menopause in women. Ann Intern Med. 1985;103:350–6. [PubMed] [Google Scholar]
65. Andersen FS, Transbol I, Christiansen C. Is cigarette smoking a promoter of the menopause. Acta Med Scand. 1982;212:137–9. [PubMed] [Google Scholar]
66. Hiatt RA, Fireman BH. Smoking, menopause, and breast cancer. J Natl Cancer Inst. 1986;76:833–8. [PubMed] [Google Scholar]
67. Hartz AJ, Kelber S, Borkowf H, et al. The association of smoking with clinical indicators of altered sex steroids—a study of 50,145 women. Pub Health Rep. 1987;102:254–9.[PMC free article] [PubMed] [Google Scholar]
68. Brambilla DJ, McKinlay SM. A prospective study of factors affecting age at menopause. J Clin Epidemiol. 1989;42:1031–9. [PubMed] [Google Scholar]
69. Willett W, Stampfer MJ, Bain C, et al. Cigarette smoking, relative weight and menopause. Am J Epidemiol. 1983;117:651–8. [PubMed] [Google Scholar]
70. Snieder H, MacGregor AJ, Spector ID. Genes control cessation of a woman's reproductive life: a twin study of hysterectomy and age at menopause. J Clin Endocrinol Met. 1998;83:1875–80. [PubMed] [Google Scholar]
71. Castelo-Branco C, Blümel JE, Chedraui P, et al. Age at menopause in Latin America. Menopause. 2006;13:706–12. Erratum in: Menopause 2006;13:850. [PubMed] [Google Scholar]
72. Gonzales GF, Villena A. Age at menopause in central Andean Peruvian women. Menopause. 1997;4:32–8.[Google Scholar]
73. McCarthy T. The prevalence of symptoms in menopausal women in the Far East: Singapore segment. Maturitas. 1994;19:199–204. [PubMed] [Google Scholar]
74. Samil RS, Wishnuwardhani SD. Health of Indonesian women, city-dwellers of perimenopausal age. Maturitas. 1994;19:191–7. [PubMed] [Google Scholar]
75. Wasti S, Robinson SC, Akhtar Y, et al. Characteristics of menopause in three groups in Karachi, Pakistan. Maturitas. 1993;16:61–9. [PubMed] [Google Scholar]
76. Blumel J, Cubillos M, Brandt A, et al. Some clinical aspects of menopause. Rev Chil Obstet Ginecol. 1988;53:278–82. [PubMed] [Google Scholar]
77. Kapoor AK, Kapoor S. The effects of high altitude on age at menarche and menopause. J Biometeor. 1986;30:21–6. [PubMed] [Google Scholar]
78. Beall CM. Ages at menopause and menarche in a high altitude Himalayan population. Ann Hum Biol. 1983;10:365–70. [PubMed] [Google Scholar]
79. Flint MP. PhD dissertation. City University of New York; 1974. Menarche and menopause in Rajput women. [Google Scholar]
80. Otolorin EO, Adeyefa I, Osotimehin BO, et al. Clinical, hormonal and biochemical features of menopausal women in Ibadan, Nigeria. Afr J Med Sci. 1989;18:251–5. [PubMed] [Google Scholar]
81. Beyene Y. Cultural significance and physiological manifestations of menopause, a bicultural analysis. Culture Med Psychiatr. 1986;10:47–71. [PubMed] [Google Scholar]
82. Boulet M. The menopause and the climacteric in seven Asian countries. In: Sixth International Congress on the Menopause. Parthenon; New Jersey: 1990. [Google Scholar]
83. Chompootweep S, Tankeyoon M, Yamarat K, et al. The menopausal age and climacteric complaints in Thai women in Bangkok. Maturitas. 1993;17:63–71. [PubMed] [Google Scholar]
84. Ramoso-Jalbuena J. Climacteric Filipino women: a preliminary survey in the Philippines. Maturitas. 19:183–90. [PubMed] [Google Scholar]
85. Lawlor DA, Ebrahim S, Smith GD. The association of socio-economic position across the life course and age at menopause: the British Women's Heart and Health Study. Br J Obstet Gynecol. 2003;110:1078–87. [PubMed] [Google Scholar]
86. Santoro N, Brockwell S, Johnston J, et al. Helping midlife women predict the onset of the final menses: SWAN, the Study of Women's Health Across the Nation. Menopause. 2007;14:415–24. [PubMed] [Google Scholar]
87. Hardy R, Kuh D. Social and environmental conditions across the life course and age at menopause in a British birth cohort study. BJOG. 2005;112:346–54. [PubMed] [Google Scholar]
88. Mishra G, Hardy R, Kuh D. Are the effects of risk factors for timing of menopause modified by age? Results from a British birth cohort study. Menopause. 2007;14:717–24. [PubMed] [Google Scholar]
89. Brand PC, Lehert PH. A new way of looking at environmental variables that may affect the age at menopause. Maturitas. 1978;1:121–32. [PubMed] [Google Scholar]

Average Age Of Dating Begins In Usa 2020

90. McKinlay S, Jefferys M, Thompson B. An investigation of the age at menopause. J Biosoc Sci. 1972;4:161–73. [PubMed] [Google Scholar]
91. Whelan EA, Sandler DP, McConnaughey DR, et al. Menstrual and reproductive characteristics and age at natural menopause. Am J Epidemiol. 1990;131:625–32. [PubMed] [Google Scholar]
92. Treloar AE, Boynton RE, Behn BG, et al. Variation of the human menstrual cycle through reproductive life. Int J Fertil. 1966;12(Pt 2):77–126. [PubMed] [Google Scholar]
93. Soberon J, Calderon JJ, Goldzieher JW. Relation of parity to age at menopause. Am J Obstet Gynecol. 1966;96:96–100. [PubMed] [Google Scholar]
94. Dorjgochoo T, Kallianpur A, Gao Y-T, et al. Dietary and lifestyle predictors of age at natural menopause and reproductive span in the Shanghai Women's Health Study. Menopause. 2008;15:924–33.[PMC free article] [PubMed] [Google Scholar]
95. Loh FH, Khin LW, Saw SM, et al. The age of menopause and the menopause transition in a multiracial population: a nation-wide Singapore study. Maturitas. 2005;52:169–80. [PubMed] [Google Scholar]
96. Reynolds RF, Obermeyer CM. Age at natural menopause in Spain and the United States: results from the DAMES project. Am J Hum Biol. 2005;17:331–40. [PubMed] [Google Scholar]
97. Parazzini F, Negri E, LaVecchia C. Reproductive and general lifestyle determinants of age at menopause. Maturitas. 1992;15:141–9. [PubMed] [Google Scholar]
98. van Keep PA, Brand PC, Lehert PH. Factors affecting the age at menopause. J Biosoc Sci Suppl. 1979;6:37–55. [PubMed] [Google Scholar]
99. Lindquist O, Bengtsson C. Menopausal age in relation to smoking. Acta Med Scand. 1979;205:73–7. [PubMed] [Google Scholar]
100. Daniell HWP. Smoking, obesity, and the menopause. Lancet. 1978;2:373. [PubMed] [Google Scholar]
101. den Tonkelaar I, Seidell J. Fat distribution in relation to age, degree of obesity, smoking habits, parity and estrogen use: a cross-sectional study of 11,825 Dutch women participating in the DOM project. Int J Obesity. 1990;14:753–61. [PubMed] [Google Scholar]
102. Kaufman DW, Slone D, Rosenberg L, et al. Cigarette smoking and age at natural menopause. Am J Public Health. 1980;70:420–2.[PMC free article] [PubMed] [Google Scholar]
103. Kaye S, Folsom A, Prineas RJ, et al. The association of body fat distribution with lifestyle and reproductive factors in a population study of postmenopausal women. Int J Obesity. 1990;14:583–91. [PubMed] [Google Scholar]
104. Kok HS, van Asselt KM, van der Schouw YT, et al. Genetic studies to identify genes underlying menopause age. Hum Reprod Update. 2005;11:483–93. [PubMed] [Google Scholar]
105. Van Asselt KM, Kok HS, Pearson PL, et al. Heritability of menopausal age in mothers and daughters. Fertil Steril. 2004;82:1348–51. [PubMed] [Google Scholar]
106. Torgerson DJ, Thomas RE, Reid DM. Mothers and daughters menopausal ages: is there a link? Eur J Obstet Gynecol Reprod Biol. 1997;74:63–6. [PubMed] [Google Scholar]
107. Cramer DW, Xu H, Harlow BL. Family history as a predictor of early menopause. Fertil Steril. 1995;64:740–5. [PubMed] [Google Scholar]
108. DeBruin JP, Bovenhuis H, VanNoord PA, et al. The role of genetic factors in age at natural menopause. Hum Reprod. 2001;16:2014–8. [PubMed] [Google Scholar]
109. Murabito JM, Yang Q, Fox C, et al. Heritability of age at natural menopause in the Framingham Heart Study. J Clin Endocrinol Metab. 2005;90:3427–30. [PubMed] [Google Scholar]
110. Stolk L, Zhai G, Van Meurs JB, et al. Loci at chromosomes 13, 19 and 20 influence age at natural menopause. Nat Genet. 2009;41:645–7.[PMC free article] [PubMed] [Google Scholar]
111. Weel AE, Uitterlinden AG, Westendorp IC, et al. Estrogen receptor polymorphism predicts the onset of natural and surgical menopause. J Clin Endocrinol Metab. 1999;84:3146–50. [PubMed] [Google Scholar]
112. He C, Kraft P, Chen C, et al. Genome-wide association studies identify loci associated with age at menarche and age at natural menopause. Nat Genet. 2009;41:724–8.[PMC free article] [PubMed] [Google Scholar]
113. He C, Kraft P, Chasman DI, et al. A large-scale candidate gene association study of age at menarche and age at natural menopause. Hum Genet. 2010;128:515–27.[PMC free article] [PubMed] [Google Scholar]
114. Lu Y, Liu P, Recker RR, et al. TNFRSF11A and TNFSF11 are associated with age at menarche and natural menopause in white women. Menopause. 2010;17:1048–54.[PMC free article] [PubMed] [Google Scholar]
115. Hardy R, Kuh D. Does early growth influence timing of the menopause? Evidence from a British birth cohort. Hum Reprod. 2002;17:2474–9. [PubMed] [Google Scholar]

Average Age Of Dating Begins In Usa Today

116. Cresswell JL, Egger P, Fall CH, et al. Is the age of menopause determined in-utero? Early Hum Dev. 1997;49:143–8. [PubMed] [Google Scholar]
117. Treloar SA, Sadrzadeh S, Do KA, et al. Birth weight and age at menopause in Australian female twin pairs: exploration of the fetal origin hypothesis. Hum Reprod. 2000;15:55–9. [PubMed] [Google Scholar]
118. Kuh D, Butterworth S, Kok H, et al. Childhood cognitive ability and age at menopause: evidence from two cohort studies. Menopause. 2005;12:475–82. [PubMed] [Google Scholar]
119. Richards M, Kuh D, Hardy R, et al. Lifetime cognitive function and timing of the natural menopause. Neurology. 1999;53:308–14. [PubMed] [Google Scholar]
120. Whalley LJ, Fox HC, Starr JM, et al. Age at natural menopause and cognition. Maturitas. 2004;49:148–56. [PubMed] [Google Scholar]
121. Kinney A, Kline J, Levin B. Alcohol, caffeine and smoking in relation to age at menopause. Maturitas. 2006;54:27–38. [PubMed] [Google Scholar]
122. McKinlay SM, Brambilla DJ, Posner JG. The normal menopause transition. Maturitas. 1992;14:103–15. [PubMed] [Google Scholar]
123. Adena MA, Gallagher HG. Cigarette smoking and the age at menopause. Ann Human Biol. 1982;9:121–30. [PubMed] [Google Scholar]
124. Jick H, Porter J, Morrison AS. Relation between smoking and age of natural menopause. Lancet. 1977;1:1354–5. [PubMed] [Google Scholar]
125. Midgett AS, Baron JA. Cigarette smoking and the risk of natural menopause. Epidemiol. 1990;1:464–80.[Google Scholar]
126. Mattison DR, Thorgierssen SS. Smoking and industrial pollution and their effects on menopause and ovarian cancer. Lancet. 1978;1:187–8. [PubMed] [Google Scholar]
127. Essenberg JM, Fagan L, Malerstein AJ. Chronic poisoning of the ovaries and testes of albino rats and mice by nicotine and cigarette smoke. West J Surg Obstet Gynecol. 1951;59:27–32. [PubMed] [Google Scholar]
128. Hart P, Farrell GC, Cooksley WGE, et al. Enhanced drug metabolism in cigarette smokers. Br Med J. 1976;3:147–9.[PMC free article] [PubMed] [Google Scholar]
129. Michnovicz J, Hershcopf R, Naganuma H, et al. Increased 2-hydroxylation of estradiol as a possible mechanism for the anti-estrogenic effect of cigarette smoking. N Engl J Med. 1986;315:1305–9. [PubMed] [Google Scholar]
130. Krailo MD, Pike MC. Estimation of the distribution of the age at natural menopause from prevalence data. Am J Epidemiol. 1983;117:356–61. [PubMed] [Google Scholar]
131. Everson RB, Sandler DP, Wilcox AJ, et al. Effect of passive exposure to smoking on age at natural menopause. Br Med J. 1986;293:792.[PMC free article] [PubMed] [Google Scholar]

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132. Mamelle N, Laumon B, Lazar P. Prematurity and occupational activity during pregnancy. Am J Epidemiol. 1984;119:309–22. [PubMed] [Google Scholar]
133. McDonald AD, McDonald JC, Armstrong B, et al. Fetal death and work in pregnancy. Br J Ind Med. 1988;45:148–57.[PMC free article] [PubMed] [Google Scholar]
Avaerage Age Of Dating Begins In Usa
134. Beaumont JJ, Swan SH, Hammond SK, et al. Historical cohort investigation of spontaneous abortion in the Semiconductor health Study: methods and analyses of risk in fabrication overall and in fabrication work groups. Am J Ind Med. 1995;28:735–50. [PubMed] [Google Scholar]
135. Swan SH, Beaumont JJ, Hammond SK, et al. Historical cohort study of spontaneous abortion among fabrication workers in the Semiconductor Health Study; agent-level analysis. Am J Ind Med. 1995;28:751–70. [PubMed] [Google Scholar]
136. Ng TP, Foo SC, Young T. Menstrual function in workers exposed to toluene. Br J Ind Med. 1992;49:799–803.[PMC free article] [PubMed] [Google Scholar]
137. Messing K, Saurel-Cubizolles MG, Bourgine M, et al. Menstrual cycle characteristics and work condition of workers in poultry slaughterhouses and canneries. Scand J Work Environ Health. 1992;18:302–9. [PubMed] [Google Scholar]
138. Eskenazi B, Gold EB, Samuels SJ, et al. Prospective assessment of fecundability of female semiconductor workers. Am J Ind Med. 1995;28:817–32. [PubMed] [Google Scholar]
139. Gold EB, Eskenazi B, Hammond SK, et al. Prospectively assessed menstrual cycle characteristics in female wafer-fabrication and nonfabrication semiconductor employees. Am J Ind Med. 1995;28:799–816. [PubMed] [Google Scholar]
140. Falck F, Jr, Ricci A, Jr, Wolff MS, et al. Pesticides and polychlorinated biphenyl residues in human breast lipids and their relation to breast cancer. Arch Environ Health. 1992;47:143–6. [PubMed] [Google Scholar]
141. Wolff MS, Toniolo PG, Lee EW, et al. Blood levels of organochlorine residues and risk of breast cancer. J Natl Cancer Inst. 1993;85:648–52. [PubMed] [Google Scholar]
142. Krieger N, Wolff MS, Hiatt RA, et al. Breast cancer and serum organochlorines: a prospective study among white, black and Asian women. J Natl Cancer Inst. 1994;86:589–99. [PubMed] [Google Scholar]
143. Hunter DJ, Hankinson SE, Laden F, et al. Plasma organochlorine levels and risk of breast cancer. N Engl J Med. 1997;337:1253–8. [PubMed] [Google Scholar]
144. Eskenazi B, Warner M, Marks AR, et al. Serum dioxin concentrations and age at menopause. Environ Health Perspect. 2005;113:858–62.[PMC free article] [PubMed] [Google Scholar]
145. Cooper GS, Savitz DA, Millikan R, et al. Organochlorine exposure and age at natural menopause. Epidemiol. 2002;13:729–33. [PubMed] [Google Scholar]
146. Cummings SR, Kelsey J, Nevitt MC, et al. Epidemiology of osteoporosis and osteoporotic fractures. Epidemiol Rev. 1985;7:178–208. [PubMed] [Google Scholar]
147. Bonen A, Ling WH, Belcastro AN, et al. Profiles of selected hormones during menstrual cycles of teenage athletes. J Appl Physiol. 1981;50:545–51. [PubMed] [Google Scholar]
148. Jurkowski JE, Joanes NL, Walker C, et al. Ovarian hormonal responses to exercise. J Appl Physiol. 1978;44:109–14. [PubMed] [Google Scholar]
149. Loucks AB, Mortola LF, Girtoon L, et al. Alterations in the hypothalamic-pituitary-ovarian and the hypothalamic-pituitary-adrenal axes in athletic women. J Clin Endocrinol Metab. 1989;68:402–11. [PubMed] [Google Scholar]
150. Jasienska G, Ziomkiewicz A, Thune I, et al. Habitual physical activity and estradiol levels in women of reproductive age. Eur J Cancer Prev. 2006;15:439–45. [PubMed] [Google Scholar]
151. Bernstein L, Ross RK, Lobo RA, et al. The effects of moderate physical activity on menstrual cycle patterns in adolescence: implications for breast cancer prevention. Br J Cancer. 1987;55:681–5.[PMC free article] [PubMed] [Google Scholar]
152. Loucks AB, Horvath SM. Athletic amenorrhea: a review. Med Sci Sports Exer. 1985;17:56–72. [PubMed] [Google Scholar]

Average Age Of Dating Begins In Usa Today

153. Scragg RFR. Menopause and reproductive span in rural Nuigini. Proc Ann Symp Papua New Guinea Med Soc. 1973:126–44.[Google Scholar]
154. Baird DD, Trlavsky FA, Anderson JJB. Do vegetarians have earlier menopause? Proc Soc Epidemiol Res. 1988:907–8.[Google Scholar]
155. Nagata C, Takatsuka N, Kawakami N, et al. Association of diet with the onset of menopause in Japanese women. Am J Epidemiol. 2000;152:863–7. [PubMed] [Google Scholar]
156. Nagata C, Takatsuka N, Inaba S, et al. Association of diet and other lifestyle with onset of menopause in Japanese women. Maturitas. 1998;29:105–13. [PubMed] [Google Scholar]
157. Nagel G, Altenburg HP, Nieters A, et al. Reproductive and dietary determinants of the age at menopause in EPIC-Heidelberg. Maturitas. 2005;52:337–47. [PubMed] [Google Scholar]
158. Hill PB, Garbaczewski L, Daynes G, et al. Gonadotrophin release and meat consumption in vegetarian women. Am J Clin Nutr. 1986;43:37–41. [PubMed] [Google Scholar]
159. Adlercreutz H, Mousavi Y, Loukovaara M, et al. Lignans, isoflavones, sex hormone metabolism and breast cancer. In: Hochberg R, Naftolin F, editors. The new biology of steroid hormones. Raven Press; New York: 1992. pp. 145–54. [Google Scholar]
160. Martin LJ, Greenberg CV, Kriukov V, et al. Intervention with a low-fat, high-carbohydrate diet does not influence the timing of menopause. Am J Clin Nutr. 2006;84:920–8. [PubMed] [Google Scholar]

Average Age Of Dating

161. Cassidy A, Bingham S, Setchell KDR. Biological effects of a diet of soy protein rich in isoflavones on the menstrual cycle of premenopausal women. Am J Clin Nutr. 1994;60:333–40. [PubMed] [Google Scholar]
162. Baird DD, Umbach DM, Lansdell L, et al. Dietary intervention study to assess estrogenicity of dietary soy among postmenopausal women. J Clin Endocrinol Metab. 1995;80:1685–90. [PubMed] [Google Scholar]

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Though it's probably something you could've guessed, given that as a culture, we're getting less and less traditional as time goes on, a new study has confirmed it: We're having babies later in life than we used to. Women are now more likely to have their first child in their early 30s than they are to begin their family in their 20s.

According to the report from the Centers for Disease Control and Prevention, this change only came about last year. For the 30 years prior, women had been mostly likely to give birth to their first child in their late 20s. However, in 2016, the birth rate for women ages 30 to 34 was 103 per 1,000, compared to the rate of 102 for women between the ages of 25 to 29. On average, women still give birth for the first time in their late twenties — at age 28, to be exact. The study also found that while teen birth rates are down, as is the overall birth rate, infant mortality rates have stayed about the same.

Though the study purely states statistical findings, there are many reasons why women may be waiting longer to have children — or not having them at all. Despite societal pressure, not all women feel compelled to become mothers, and changing attitudes about gender are encouraging more women to make whatever decision feels right for them. Advances in medicine, such as in vitro fertilization and egg-freezing, are allowing women to wait longer to have children while feeling less pressured by biology. Regardless of what you decide for yourself, however, once you hit age 28, brace yourself for many more newborns in your Instagram and Facebook feeds.

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