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

Abstract

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 PM2.5 and NO2 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/m3 increase in air pollution]. In the multiple-pollutant models, the NO2–menopause associations were attenuated after adjusting for PM2.5 and O3, whereas the associations of menopause with PM2.5 and O3 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.