Cigarette smoking affects timing of menopause
Cigarette smoking appears to have a dose-response association with the risk of early menopause among both current smokers and past smokers, according to a study.
Researchers used data from the Nurses’ Health Study II involving 116,429 nurses, among whom 69,881 reported never smoking (mean age at baseline 33.7 years), 22,619 reported past smoking (mean age at baseline 35 years) and 13,756 reported current smoking (mean age at baseline 34.4 years).
Current smokers were 1.9 times (95 percent CI, 1.71 to 2.11) as likely as never smokers to experience early menopause. The risk was 1.1-fold (1.00 to 1.21) higher among former vs never smokers.
A clear dose-response effect of smoking was observed on the risk of early menopause, such that the risk increased with increasing levels of pack-years among women reporting current smoking. The hazard ratios (HRs) were 1.72 (1.36, 2.18) with 11 to 15 pack-years, 1.72 (1.38 to 2.14) with 16 to 20 pack-years, and 2.42 (2.11 to 2.77) with >20 pack-years.
Likewise, increased risk of early menopause was seen among former smokers reporting 11 to 15 pack-years (HR, 1.29; 1.07 to 1.55), 16 to 20 pack-years (HR, 1.42; 1.13 to 1.79) or >20 pack-years (HR, 1.54; 1.23 to 1.93).
The risk did not particularly differ between never smokers and women who smoked ≤10 cigarettes/day but quit by the age of 25 years (HR, 1.03; 0.91 to 1.17).
Researchers explained that cigarette smoking may influence timing of menopause through the acute effects on gonadotropin and sex steroid levels or through direct toxic effects on ovarian follicles, as cigarette smoke constitutes nicotine and polycyclic hydrocarbons, which block aromatase conversion of androgens into oestrogens in animal models, as well as lower blood levels of oestrogen and peak luteinizing hormone.
Early menopause or cessation of ovarian function before the age of 45 years affects roughly 5 to 10 percent of Western women and is associated with increased risk of premature mortality and cognitive decline, osteoporosis, cardiovascular disease, and other adverse health outcomes. [Maturitas 2010;65:161–166; Menopause 2012;19(10):1081–1087; Menopause 2013;20(11):1139–46]