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Over the 6 decades, the mean age at natural menopause increased from 48.4 years to 49.9 years (P < 0.001 for trend).
During the same time period, the mean reproductive life span rose from 35.0 years to 37.1 years (P < 0.001 for trend), while the mean age at menarche declined from 13.5 years to 12.7 years (P < 0.001 for trend).
This longer reproductive life span is attributed to both an increased age at natural menopause and an earlier age at menarche, according to a research letter in JAMA.
“Understanding changes in the timing of age at natural menopause and length of the reproductive life span, and associated factors, are important because these issues influence multiple health conditions,” said lead author Duke Appiah, PhD, MPH, an assistant professor of public health and director of the master of public health program at Texas Tech University Health Sciences Center in Lubbock, Texas.
For instance, earlier age at natural menopause is reported to be linked to cardiovascular diseases, neurological diseases, and osteoporosis risk, according to Appiah, whereas later menopause has been connected to increased risk of breast, endometrial, and ovarian cancers.
“Overall, longer reproductive life spans are associated with reduced morbidity and mortality,” Appiah told Contemporary OB/GYN®.
Study data was collected by the National Center for Health Statistics (NCHS). The 2 successive surveys were the National Health Examination Survey I (NHES I; 1959-1962) and the National Health and Nutrition Examination Surgery (NHANES) for 1971 to 2018.
The response rate was 87% for the earlier survey and 49% for the latter survey.
Ages at menarche and menopause were self-reported. A total of 7,773 women aged 40 to 74 years with natural menopause and no missing age at menopause were included in the analysis.
“The increases in the mean age at natural menopause and reproductive lifespan were anticipated, as reports from several countries point toward increasing trends in age at natural menopause,” Appiah said.
The study also found that Black or Hispanic race/ethnicity, poverty, current and former smoking status, and hormone therapy were linked to earlier age at natural menopause and shorter reproductive lifespan.
“Conversely, greater years of education and oral contraceptive use were associated with later age at natural menopause and longer reproductive lifespan,” Appiah said.
Additionally, because American women are adopting healthier lifestyles “as evidenced by the decrease in the proportion of current smokers, coupled with increasing use of oral contraceptives and additional years of education, we anticipate that the mean age at natural menopause for American women will continue to increase, similar to that reported for other industrialized countries,” Appiah said.
Whether the increase in age at natural menopause over the study period has clinical significance for women’s health, apart from reproduction, is unknown, according to the authors.
“Future studies from a variety of disciplines are needed to determine why age at natural menopause is associated with certain chronic diseases,” Appiah said.
Appiah reports no relevant financial disclosures.