Association of ambient air pollution and age at menopause: a population-based cohort study in Tehran, Iran

Menopause is influenced by various factors including age, lifestyle, and environmental factors. Whether long-term exposure to ambient air pollutants is associated with a decrease in menopausal age requires further study. In this study, we investigated the association between ambient air pollutants with decreasing menopausal age in women participating in the Tehran Lipid and Glucose Study (TLGS). The study population were reproductive aged women who participated in TLGS. The annual average concentrations of pollutants including NO, NO2, NOX, PM10, PM2.5, SO2, benzene, toluene, ethylbenzene, p-xylene, m-xylene, o-xylene (BTEX), and total BTEX for each person were estimated based on the residence addresses, the date, and duration of their residence at each address using previously developed land use regression (LUR) models. The multivariable Cox proportional hazards regression model was used to estimate the hazard ratio (HR) with 95% confidence intervals (CI) between the tertiles of study air pollutants and age at menopause, after adjustment for enter age, BMI, smoking, physical activity, menarche age, education, marital status, and parity (number of deliveries). Additionally, the associations between menopausal age and the air pollutants exposures were estimated using multivariable linear regression. There was no statistically significant association between the hazard of menopause event and tertiles of exposure to air pollutants by Cox proportional hazard models. The multiple linear regression model revealed that despite observing a negative association between air pollutants with age at menopause, this association was not statistically significant. We found associations between air pollution and reduction in menopausal age but that were not statistically significant. Further research with larger sample size is recommended for future studies.