Association of Short-Term Exposure to Air Pollution with Depression in Patients with Asthma: A Cross-Sectional Study in Delhi, India.

Background: Patients with asthma are a population at risk for depression and subsequent mental health risks. Previous studies have suggested that exposure to air pollution is associated with lower asthma control and a higher risk of depression. There is limited evidence on the effect of short-term exposure to air pollution on mental health in susceptible populations, such as patients with asthma.

Objectives: The objective of the present study was to assess the association between short-term exposure ( $\le 30d$ ) to air pollution and depression in patients with asthma.

Methods: This hospital-based cross-sectional study included 151 consecutively recruited 18- to 65-y-old patients with asthma from two sites in Delhi, India. The Asthma Control Test and the Patient Health Questionnaire-9 were respectively used to assess asthma control and depression status. Data on particulate matter [PM $\le 10\text{\hspace{0.17em}and\hspace{0.17em}}2.5\mu m$ in aerodynamic diameter ( ${\mathrm{PM}}_{10}$ and ${\mathrm{PM}}_{2.5}$ , respectively)], nitrogen dioxide ( ${\mathrm{NO}}_2$ ), sulfur dioxide ( ${\mathrm{SO}}_2$ ), carbon monoxide (CO), and ozone ( $O_3$ ) were procured from Central Pollution Control Board (CPCB) air quality monitors, and 1-month average exposures were computed using inverse distance weighting (IDW) based on participant residence and workplace address. Ordinal and binary logistic regressions were respectively used to assess the associations for depression status and asthma control with per-unit interquartile range (IQR) increase of air pollution exposure. Sensitivity analyses were conducted using two-pollutant models and mediation effects were evaluated using the Karlson-Holm-Breen method.

Results: Among all participants, 58.3% exhibited depression, and 73.5% had uncontrolled asthma. Adjusted ordinal regression revealed significant associations of ${\mathrm{PM}}_{10}$ , ${\mathrm{PM}}_{2.5}$ , ${\mathrm{NO}}_2$ , and ${\mathrm{SO}}_2$ with increased severity of depression [adjusted odds ratio (aOR) for IQR increase for ${\mathrm{PM}}_{10}=1.65$ (95% CI: 1.27, 2.16), ${\mathrm{PM}}_{2.5}=1.65$ (95% CI: 1.22, 2.22), ${\mathrm{NO}}_2=2.49$ (95% CI: 1.31, 4.73), and ${\mathrm{SO}}_2=1.35$ (95% CI: 1.09, 1.66)]. Similarly, each IQR increase in these pollutants corresponded to significantly lower odds of asthma control [aOR for IQR increase for ${\mathrm{PM}}_{10}=0.72$ (95% CI: 0.50, 0.98), ${\mathrm{PM}}_{2.5}=0.68$ (95% CI: 0.47, 0.99), ${\mathrm{NO}}_2=0.29$ (95% CI: 0.13, 0.65), and ${\mathrm{SO}}_2=0.67$ (95% CI: 0.47, 0.97)]. Asthma control significantly mediated 24.97% and 25.84% of the association of ${\mathrm{NO}}_2$ and ${\mathrm{SO}}_2$ exposure, respectively, with depression status. $O_3$ exposure was not associated with depression status or asthma control.

Conclusions: Our study shows that greater short-term exposure to air pollution may be associated with increased odds of depression and uncontrolled asthma in patients with asthma. Further studies are required to replicate our results and confirm this association. https://doi.org/10.1289/JHP1003.