Underweight at early, mid-adulthood tied to early menopause risk
Women who are underweight, particularly in their late teens and mid-thirties, may be at risk for early menopause, a recent study found.
“Up to 10 percent 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,” said study author Dr Kathleen Szegda from the University of Massachusetts, Amherst, Massachusetts, US.
“Our findings suggest that women who are underweight in early or mid-adulthood may be at increased risk for early menopause … so these findings have important implications for women and their doctors,” she said.
The study cohort comprised 78,759 women aged 25–42 years (premenopausal at baseline, mean age 34.8 years) from the prospective Nurses’ Health Study II who were followed-up from 1989 (baseline) to 2011. Early menopause, defined in this study as natural menopause before age 45 years (amenorrhoea for 12 consecutive months), was reported by 2,804 women.
Participants provided information on height, weight, and menopausal status at baseline, and updated menopausal cause and status, weight, hormone therapy use, and lifestyle factors every 2 years through questionnaires.
Compared with women of normal weight (BMI 18.5–22.4 kg/m2), underweight women (BMI <18.5 kg/m2) had a significantly elevated risk for early menopause (odds ratio [OR], 1.30). [Hum Reprod 2017;doi:10.1093/humrep/dex304]
In contrast, overweight women (BMI 25.0–27.4 kg/m2 and 27.5–29.9 kg/m2) were less likely to experience early menopause (OR, 0.79 and 0.70, respectively), and while obese women (BMI 30.0–34.9 kg/m2) had a reduced risk of early menopause (OR, 0.83), this risk did not extend to women with a BMI ≥35.0 kg/m2 (OR, 1.02).
Women who were underweight at age 18 (BMI <17.5 kg/m2) and 35 years (BMI <18.5 kg/m2) had significantly higher risks of early menopause compared with normal weight women (OR, 1.54 and 1.59, respectively), while the risk was lower in women who were overweight at age 35 years (BMI 27.5–29.9 kg/m2; OR, 0.71).
Underweight women (BMI <18.5 kg/m2) who had severe weight cycling (loss of ≥20 pounds ≥3 times between age 18 and 30 years) had twice the risk of early menopause than non-cyclers (OR, 2.40), though there were only seven women included in this analysis.
According to Szegda, the mechanisms behind the underweight-early menopause link are not clearly understood.
An increased “risk for functional hypothalamic amenorrhoea” due to low body weight, is one reason postulated by Szegda and colleagues. Another reason is the “increased activation of the hypothalamic-pituitary-adrenal axis”, which in turn, leads to an increase in corticotrophin releasing hormone, adrenocorticotrophin, and cortisol levels, of which chronic elevations may result in a higher risk of early menopause, they said.
Future research avenues include determining the mechanisms behind the association, identifying the link between birth weight, adiposity in early life, and menopause timing, and whether the association applies to different ethnicities, as this study population was predominantly Caucasian, said the researchers.
These results are also limited to early natural menopause and not surgical menopause or menopause due to cancer, they said.