Underweight women have high risk of early menopause

Underweight women have a significantly greater risk of experiencing early menopause compared with lean or overweight women, researchers reported in Human Reproduction.

In a Nurses’ Health Study II, monitored from 1989 to 2011, Kathleen Szegda, PhD, MPH, MS, from the Department of Biostatistics & Epidemiology, School of Public Health & Health Sciences at the University of Massachusetts in Amherst, and colleagues included 78,759 premenopausal women to test the likelihood of natural early menopause, defined as menopause occurring without the facilitation of health issues such as hysterectomies, oophorectomies, or cancers before or at the age of 45.

Participants were asked to report their weight (at age 18 years and current) and height, which were used to determine weight change and BMI. Reported BMIs were categorized into 7 groups (lowest BMI group, <18.5kg/m²; highest BMI group, ≥35.0 kg/m²). Women who were recorded as being underweight at age 18 were subdivided into a <17.5 kg/m² group and a 17.5 kg/m²-18.5 kg/m² group. Those who had a weight change 3 or more times, losing 20 or more pounds (severe) and losing 10 or more pounds (mild), from age 18 years to the end of this study were monitored closely and compared with normal, lean women.

The patients were asked if they were smokers or non-smokers but were not screened for anorexia nervosa, irritable bowel syndrome, or autoimmune disorders, which might facilitate weight loss or fluctuation.

Compared with lean-normal weight women (BMI, 18.5-22.4kg/m²) the underweight subjects (BMI, <18.5 kg/m²) had a 30% increased odds of early menopause. Odds were much lower with obese women (BMI, 30.0-34.9 kg/m²) and overweight women (BMI, 25.0-27.4 kg/m²), who had odds ratios of 0.83 and 0.70, respectively.

Among the participants, 3.56% of the population had a natural early menopause. Weight cycling from ages 18 to 30 years did not indicate any risk of early menopause. The study did not find increased odds of early menopause in either smoking or non-smoking women, although the risk of early menopause increased greatly in underweight smokers (OR, 1.40). The researchers theorize that this may be due to compounds in cigarettes linked to ovarian toxicity.

Although the study concludes that underweight women, primarily those with serious weight fluctuations, have a greater risk of earlier menopause than overweight women, the authors plan to expand their research to include a wider range of ethnic groups (this study focused predominantly on white, non-Hispanic women). They also plan to include more variables to monitor health risks associated with early menopause.

“This is among the first prospective studies to focus specifically on adiposity and early menopause, which has been associated with increased risk for cardiovascular disease and other health conditions,” the researchers stated.

1. Szegda KL, Whitcomb BW, Purdue-Smithe AC, Boutot ME, Manson JE, Hankinson SE, et al. Adult adiposity and risk of early menopause. Hum Reprod. 2017 Oct 25.  doi: 10.1093/humrep/dex304