Passive smoking is associated with lower age at menopause.

Objective: The aim of the study was to investigate the age at menopause in women exposed to passive smoking.

Methods: The study was designed as a case-control study. The main outcome measure was to compare the age at menopause of women exposed to second-hand smoking to non-exposed women.

Results: The age at menopause in the group exposed to second-hand smoking was significantly lower than that of women in the non-exposed group (47.0 ± 4.7 vs. 48.1 ± 5.2 years, p = 0.002). In regression analyses, the age at menopause had an inverse correlation with second-hand smoking, and a positive correlation with the mother's age at menopause. We further stratified women according to their smoking status. Women exposed to second-hand smoking who had never smoked had a significantly lower age at menopause than the non-exposed women only when the duration of exposure exceeded 20 years (46.6 ± 5.6 vs. 48.4 ± 3.7 years, p = 0.008). Furthermore, women who had never smoked and who were exposed to ≥ 10 cigarettes per day had a significantly lower mean age at menopause than non-exposed women who had never smoked. These differences were not observed among women who had ever smoked.

Conclusions: Our findings suggest that earlier age at menopause should be added to the negative effects of passive smoking, in addition to increased risks for overall, cardiovascular and cancer mortality as well as increased risk for osteoporosis.