Long-term effects of ambient air pollutants on suicidal ideation in China: The Henan Rural Cohort Study

Background The association between ambient air pollutants exposure and suicidal ideation (SI) has rarely been explored, especially in Chinese population. Therefore, we aimed to investigate the long-term effects of ambient air pollutants on SI among a Chinese rural population. Method We recruited 29997 participants from the Henan Rural Cohort study in 2016–2017. SI was evaluated by using the ninth item of the Patient Health Questionnaire-9 (PHQ-9) in the baseline survey. We adopted a satellite-based spatiotemporal model to estimate participants’ exposure to particulate matters (PMs) (PM with an aerodynamic diameter ≤1 μm (PM1), ≤2.5 μm (PM2.5) or ≤10 μm (PM10), respectively) and nitrogen dioxide (NO2), and then calculated the 3-year average concentrations of the four pollutants. We used logistic regression models to explore the association between long-term exposure to ambient air pollutants and SI. In addition, we conducted several stratified analyses to examine effect modification of selected factors. Results The odds ratios (95% confidence intervals [CI]) of SI in response to each 1 μg/m3 increase in PM1, PM2.5, PM10 and NO2 concentrations were 1.08 (1.01, 1.15), 1.10 (1.02, 1.19), 1.05 (1.01, 1.09) and 1.12 (1.04, 1.21), respectively. Individuals exposed to PM1, PM2.5, PM10 or NO2 concentrations in the fourth quartile had a 1.36-fold (95%CI: 1.08, 1.72), 1.69-fold (95%CI: 1.05, 2.72), 1.49-fold (95%CI: 1.09, 2.05) or 1.71-fold (95%CI: 1.15, 2.85) risks of SI, compared to the ones with corresponding air pollutants in the first quartile. Besides, the risks of SI increased with the quartiles of air pollutants (PM1: Ptrend = 0.002, PM2.5: Ptrend = 0.003, PM10: Ptrend = 0.010, NO2: Ptrend = 0.010). Stratified analyses suggested that males, highly educated participants, ever-drinkers and people aged range 36–64 years were more vulnerable to the adverse effects of air pollutants. Conclusions This study provided evidence for the long-term effects of ambient PMs and NO2 on SI in rural Chinese adults, particularly for males, highly educated participants, ever-drinkers and people aged range 36–64 years.