Gaseous air pollution exposure and depression in middle-aged and elderly adults: evidence from a Chinese cohort†

Increasing research has investigated the impact of atmospheric gaseous air pollution on depression. However, the results have exhibited inconsistencies, and the majority of studies have focused on the impact of long- or short-term exposures. The aim of the study was to investigate the impact of intermediate-term exposure to gaseous air pollution on depression in middle-aged and older adults. In 2013, 8639 participants aged 45 and above were enrolled in the China Health and Retirement Longitudinal Study (CHARLS). Using a linear mixed-effects model, we examined the association between gaseous air pollution (NO₂, SO₂, CO, and O₃) and depression over intermediate-term exposure windows (30, 60, 90, and 180 days). Interaction and subgroup analyses were conducted to identify potential effect modifiers in the association. Every 10 μg m⁻³ increase in NO₂ and SO₂ was associated with increased depression scores, with the most pronounced effects observed in the 30 day exposure window (β = 0.55, 95% CI: 0.25–0.85) and 60 day exposure window (β = 0.75, 95% CI: 0.52–0.99), respectively. For CO, every 1 mg m⁻³ increase was associated with elevated depression scores in the 60 day exposure window (β = 1.28, 95% CI: 0.44–2.13). Interaction analyses revealed that individuals who consumed alcohol, lived in urban areas, or were married exhibited heightened susceptibility to the effects of gaseous air pollution on depression. Here, we provide the first evidence that intermediate-term gaseous air pollution exposure within specific temporal windows may substantially increase the risk of depression. It is important to prioritize individuals who consume alcohol, live in urban areas, and are married.