Long-term air pollution exposure factors in late-onset depression

Older adults with long-term residential ambient exposure to air pollutants have an increased likelihood of being diagnosed with depression, according to a study.

The study included 8,907,422 Medicare enrolees (mean age 73.7 years, 56.8 percent women, 90.2 percent White) who were at least 65 years old. Of these, 1,526,690 received late-onset depression diagnoses after 5 years of follow-up.

The participants were exposed to an annual mean fine particulate matter (PM_2.5) level of 9.6 μg/m³ and ozone (O₃) level of 39.1 parts per billion (ppb), as well as an annual median nitrogen dioxide (NO₂) level of 15.4 ppb.

Cox proportional hazards based on a tripollutant model showed that each 5-unit increase in long-term mean exposure to PM_2.5, NO₂, and O₃ was associated with an adjusted percentage increase in depression risk of 0.91 percent (95 percent confidence interval [CI], 0.02–1.81), 0.61 percent (95 percent CI, 0.31–0.92), and 2.13 percent (95 percent CI, 1.63–2.64), respectively.

Effect size heterogeneity was found among subpopulations by comorbidity condition and neighbourhood contextual backgrounds. Specifically, the risk of developing late-life depression after being exposed to long-term air pollution was pronounced for older adults who were socioeconomically disadvantaged and those with comorbidities.

The findings may have important implications for both environmental regulation and public health management.