Associations between long-term exposure to multiple air pollutants and age at menopause: a longitudinal cohort study.

Background: To investigate the associations between long-term exposure to ambient air pollution and age at menopause and the risk of early menopause in two Asian cohorts.
Methods: A total of 53,167 female adults were enrolled from two ongoing cohorts, one each in Taiwan and Hong Kong, between 2003 and 2018, yielding 200,000 person-years of follow-up. We performed a Cox regression model with time-dependent covariates to investigate associations between air pollution and menopause.
Results: The mean age at baseline and at natural menopause was 34.4 and 51.0 years, respectively. In the single-pollutant models, we found that increase in PM _2.5 and NO ₂ was associated a younger age at menopause [hazard ratios (HRs) (95% confidence interval, CI): 1.16 (1.09-1.23) and 1.04 (1.01-1.06), respectively, for each 10 µg/m ³ increase in air pollution]. In the multiple-pollutant models, the NO ₂ -menopause associations were attenuated after adjusting for PM _2.5 and O ₃ , whereas the associations of menopause with PM _2.5 and O ₃ remained stable. Similar associations were observed for the risk of early menopause (age at menopause ≤ 45 years).
Conclusions: Long-term exposure to ambient air pollution was associated with the age at menopause and the risk of early menopause. More effective strategies to mitigate air pollution are required.
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