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BMI may affect timing of menopause
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The risk for early natural menopause appears to be associated with BMI, with increased risk among underweight women and lower risk for women with overweight compared with normal-weight women, according to findings published in Human Reproduction.
“Up to 10% of women experience early menopause, and it is associated with a higher risk of cardiovascular disease and other health conditions, such as cognitive decline, osteoporosis and premature death, so these findings have important implications for women and their doctors,” Kathleen Szegda, PhD, MPH, of the department of biostatistics and epidemiology at the School of Public Health and Health Sciences at the University of Massachusetts in Amherst, said in a press release. “Underweight women may want to consider discussing the potential implications of these findings with their doctors.”
Szegda and colleagues evaluated data from the Nurses’ Health Study II on 78,759 premenopausal women (mean age at baseline, 34.8 years) followed from 1989 to 2011 for incidence of early natural menopause. Researchers sought to assess the associations between overall adiposity, weight distribution and weight change with early natural menopause. Early menopause was defined as natural menopause occurring before age 45 years.
Participants were divided into seven groups based on BMI: less than 18.5 kg/m2 (n = 2,650), 18.5 kg/m2 to 22.49 kg/m2 (n = 35,539), 22.5 kg/m2 to 24.99 kg/m2 (n = 17,581), 25 kg/m2 to 27.49 kg/m2 (n = 9,745), 27.5 kg/m2 to 29.99 kg/m2 (n = 4,413), 30 kg/m2 to 34.99 kg/m2 (n = 5,145) or at least 35 kg/m2 (n = 3,237).
Overall, 2,804 participants experienced early menopause.
Participants with BMI less than 18.5 kg/m2 had 30% higher risk for early menopause, whereas the risk was lower in participants with BMI 25 kg/m2 to 27.4 kg/m2 (OR = 0.79; 95% CI, 0.69-0.96) and BMI 27.5 kg/m2 to 29.9 kg/m2 (OR = 0.7; 95% CI, 0.58-0.84) compared with participants with lean-normal BMI. Participants with BMI 30 kg/m2 to 34.9 kg/m2 also had a lower risk compared with lean-normal-weight participants (OR = 0.83; 95% CI, 0.71-0.98).
The risk for early natural menopause was 50% higher among participants with BMI less than 17.5 kg/m2 at age 18 years compared with lean-normal-weight participants (OR = 1.54; 95% CI, 1.24-1.9). The risk for early menopause was marginally higher in participants who lost at least 20 lb from age 18 to 35 years compared with participants who gained 5.1 lb to 15 lb (OR = 1.38; 95% CI, 0.97-1.96).
Among a subset of participants who were smokers, the odds for early menopause were significantly higher for participants who were underweight (OR = 1.4; 95% CI, 1.03-1.9), whereas the odds were lower among participants with overweight (BMI 25-27.4 kg/m2, OR = 0.7; 95% CI, 0.57-0.86; BMI 27.5-30 kg/m2, OR = 0.57; 95% CI, 0.43-0.8) compared with lean normal-weight participants.
“Causes of early menopause are not clearly understood,” Szegda told Endocrine Today. “Our findings suggest that being underweight may have an impact on the timing of menopause. ... More research is needed to replicate findings and better understand how low adiposity may physiologically impact timing of menopause.” – by Amber Cox
For more information:
Kathleen Szegda , PhD, MPH, can be reached at kzegda@umass.edu.
Disclosures: The authors report no relevant financial disclosures.
Perspective
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Determining the risk factors that affect the age of menopause is important for fertility, aging and overall female health risk implications. Ten percent of women are diagnosed with early menopause (age 45 years or younger).
This large prospective cohort study strikingly reveals 30% higher odds of early menopause in underweight women (BMI, < 18.5 kg/m2), while overweight women (BMI, 25 kg/m2 to 29.9 kg/m2) had a significant 21% to 30% lower odds.
This nonlinear, J-shaped association between BMI and risk for early menopause is clinically important for several reasons. Early menopause is associated with increased health risks for CVD, osteoporosis, cognitive decline and earlier mortality. Early menopause affects fertility, which is critical in women who continue to delay childbearing.
Women with low BMI in early and mid-adulthood, particularly those who reported marked weight cycling, had a higher risk for early menopause compared to lean normal-weight women. While we would certainly not encourage being overweight to avoid early menopause, women should be counseled regarding the risks of weight cycling and being underweight as well as being grossly overweight. It is important to note that low BMI increases risk for functional hypothalamic amenorrhea, which leads to anovulation, low estrogen level and infertility.
On the flip side, blocking high follicle-stimulating hormone in mice has been recently reported to be associated with increased thermogenesis and reduced adiposity (Liu P, et al. Nature. 2017;doi:10.1038/nature22342). This is important because menopause is associated with bone loss and adipose gain. Understanding the relationship with FSH, active brown fat and ovarian function may help us understand mechanisms of obesity and chronic disease.
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