Association between outdoor and indoor air pollutant exposure and depression among middle-aged and older adults in China

Abstract

Limited epidemiological studies have explored the association between outdoor and indoor air pollutants and depressive symptoms among middle-aged and elderly adults. We utilized data from the China Health and Retirement Longitudinal Study (CHARLS). Depressive symptoms were assessed using the 10-item Center for Epidemiologic Studies Depression Scale (CES-D 10), while indoor air pollution was self-reported. Outdoor air pollutant data were obtained from the China National Environmental Monitoring Center (CNEMC). Logistic regression was used to examine the association between exposure to outdoor air pollutants and indoor air pollutants from solid fuel use and depressive symptoms among middle-aged and older adults in China. The study found that each standard deviation (SD) increase in outdoor PM_2.5 and SO₂ was significantly associated with the occurrence of depressive symptoms. Exposure to indoor air pollution from solid fuel use for heating and cooking was also significantly linked to depressive symptoms. Indoor air pollution from solid fuel use for cooking may attenuate the association between outdoor PM_2.5 and PM₁₀ and depressive symptoms on a multiplicative scale. These findings highlight a significant correlation between depressive symptoms and exposure to both outdoor and indoor air pollutants in middle-aged and elderly adults.

Keywords: Air pollutants; Depression; Indoor solid fuel use; Interaction analysis; Middle-aged and elderly adults.

Fig. 1

Sample distribution.

Fig. 2

Odds ratio and 95% CI of each SD increment of outdoor air pollutants for depression symptoms. Notes: *p < 0.05, **p < 0.001. Abbreviations: CI, confidence interval. Model 1: the unadjusted model; Model 2: model 1 adjusted for age and gender; Model 3: model 2 with additional adjustment for smoking status, drinking status, and chronic disease (hypertension, heart disease, stroke, diabetes, cancer, and dyslipidemia); Model 4: model 3 with additional controlling for race, marriage status, education level, residence, and annual household income.

Fig. 3

The relationship between each SD increment of 365-day outdoor air pollutants exposure and depressive symptoms in multivariate models: modification by indoor fuel use types. Notes: *p < 0.05, **p < 0.001. The p-value is the multiplicative interaction. Abbreviations: OR, odds ratio; CI, confidence interval. Multivariate logistic regression adjusted for age, gender, smoking status, drinking status, chronic disease (hypertension, heart disease, stroke, diabetes, cancer, and dyslipidemia), race, marriage status, education level, residence, and annual household income.

Fig. 4

The relationship between each SD increment of 365-day outdoor air pollutants exposure and depressive symptoms (cutoff 12) in multivariate models: modification by indoor fuel use types. Notes: *p < 0.05, **p < 0.001. The p-value is the multiplicative interaction. Abbreviations: OR, odds ratio; CI, confidence interval. Multivariate logistic regression adjusted for age, gender, smoking status, drinking status, chronic disease (hypertension, heart disease, stroke, diabetes, cancer, and dyslipidemia), race, marriage status, education level, residence, and annual household income.