Short-term exposure to air pollution and depressive symptoms: Findings from the French CONSTANCES cohort.

BACKGROUND

Major depressive disorders pose a substantial public health burden, with emerging evidence linking these disorders to air pollution.

OBJECTIVE

To investigate the association between short-term exposure to air pollution and depressive symptoms, focusing on particulate matter with a diameter ≤ 2.5 μm (PM2.5) and nitrogen dioxide (NO2).

METHODS

Data from the enrollment phase of the French CONSTANCES cohort (2012-2016) were analyzed cross sectionally. For each participant, we assigned the median concentrations of PM2.5 and NO2, estimated by the CHIMERE model, over the seven days preceding completion of the Centre of Epidemiologic Studies Depression (CES-D) scale to their residential addresses. We assessed depressive symptoms using the CES-D and defined clinically significant depressive symptoms (binary variable) with the validated threshold of 19. We used negative binomial regression models (yielding Incidence Rate Ratio (IRR) and 95% confidence interval (CI)) and logistic regression models (yielding Odds Ratio (OR) and 95% CI), for an interquartile range (IQR) increase in exposures, adjusted for two sets of confounders.

RESULTS

105,976 participants (mean age, 47.3 ± 13.7 years; 53% women) were included. The 7-day median PM2.5 and NO2 exposures were 8.4 µg/m3 (IQR: 5.9-12.2) and 2.2 µg/m3 (IQR: 1.3-3.5), respectively. Short-term exposures to PM2.5 and NO2 were positively associated with a higher CES-D score (IRR = 1.009 (95% CI: 1.003-1.014) and IRR = 1.009 (95% CI: 1.004-1.014), respectively) and with higher rates of clinically-significant depressive symptoms (OR = 1.027 (1.008-1.046) and OR = 1.031 (1.012-1.051), respectively). These results were consistent across sensitivity analyses. There was an interaction between BMI and exposure to NO2, with a significant effect only among subjects with obesity.

CONCLUSIONS

Our results suggest that air pollution may affect mental health, even at a subclinical level, warranting further research especially during pollution peaks. However, this study could not establish causality.