Women who smoke begin menopause a year earlier than nonsmokers, researchers concluded, adding that earlier menopause is associated with osteoporosis and heart disease.
Researchers conducted a meta-analysis of the available data about smoking and menopause, finding 11 studies comprising about 50,000 women, using age 50 as a threshold for early or late age at natural menopause (ANM). Results appeared in Menopause.
In five studies, participants were classified as early or late menopause (dichotomous). The pooled effect was an odds ratio (OR) of 0.74 (95% confidence interval [CI], 0.60 to 0.91, P less than 0.01), or, smoking increased the risk of menopause before age 50 by 43%.
In six others, mean and standard deviation were provided for smoking and nonsmoking samples (continuous), and weighted mean difference (WMD) was -1.12 (95% CI, -1.80 to -0.44, P=0.04), or, smokers incurred menopause a year earlier than nonsmokers.
After adjustment of the original data for heterogeneity, the pooled results were OR=0.67 (95% CI, 0.61 to 0.73, P less than 0.01) for dichotomous studies and WMD=-0.90 (95% CI, -1.58 to -0.21, P=0.01) for the continuous studies.
Smoking may have an antiestrogenic effects, the authors explained, which might trigger earlier menopause. For example, smoking may induce expression of CYP1A2, may decrease estrogen in the blood, or may increase metabolic 2-hydroxyestrogen.
They wrote, “Our results give further evidence that smoking is significantly associated with earlier ANM and provide yet another justification for women to avoid this habit.”
*This blog post was originally published at ACP Internist*