Polycyclic aromatic hydrocarbon exposure and depressive symptoms among middle-aged and older Chinese adults: a prospective cohort study using CHARLS data

Depressive symptoms are highly prevalent among older Chinese adults, and environmental pollutants such as PAHs may contribute to this disease burden. This study aimed to identify modifiable PAH‑related risk factors to inform targeted preventive interventions. We included 5,006 participants from the 2015 wave of the China Health and Retirement Longitudinal Study (CHARLS) who were free of depression at baseline. Exposure to 16 ambient PAHs was assigned based on annual average concentrations matched to participants’ residential counties. Incident depressive symptoms were defined as a CES‑D‑10 score ≥ 10 at the 2018 follow‑up. Multivariable logistic regression was used to estimate odds ratios (ORs), along with subgroup, interaction, and sensitivity analyses. The cumulative incidence of depressive symptoms was 21.8%. Five individual PAHs were significantly associated with depressive symptoms: acenaphthylene (Acy) was associated with a reduced risk (OR = 0.857, 95%CI: 0.780–0.940, P = 0.001), whereas benzo[k]fluoranthene (BkF; OR = 1.035), anthracene (Ant; OR = 1.136), acenaphthene (Ace; OR = 1.166), and fluorene (Flu; OR = 1.066) were associated with an elevated risk (all P < 0.05). Subgroup analyses revealed stronger associations among participants aged < 60 years (9 significant PAHs) than among those aged ≥ 60 years (no significant associations), with more significant PAH associations observed in males (4 compounds) than in females (2 compounds). Four significant interactions were identified: older age attenuated the effects of Ace, Ant, and Phe, whereas smoking significantly enhanced the pro‑depressive effect of BaP (all P < 0.05). PAH exposure is a modifiable risk factor for depressive symptoms among middle‑aged and older Chinese adults, with marked heterogeneity across demographic and behavioral subgroups. Public health strategies should include reducing solid fuel use, strengthening air quality standards, and integrating depression screening for high‑exposure populations, particularly younger males and smokers. Notably, this is the first prospective study to identify a protective association between Acy and depressive symptoms, which contrasts with the well‑documented neurotoxicity of other PAH congeners.