Particulate Air Pollutants and Trajectories of Depressive Symptoms in Older Women

ObjectivesAlthough several environmental factors contribute to the etiology of late-life depressive symptoms, the role of ambient air pollution has been understudied. Experimental data support the neurotoxicity of airborne particulate matter with aerodynamic diameter of ≤2.5 μm (PM_2.5), but it remains unclear whether long-term exposure is associated with late-life depressive symptoms. Our secondary aim was to explore whether the observed associations between exposure and depressive symptoms are explained by dementia risk.Design, Setting, and ParticipantsProspective community-dwelling cohort study from the Women's Health Initiative Study of Cognitive Aging (1999–2010). Our analyses included 1,989 older women (baseline age 73.3 ± 3.75) with no prior depression or cognitive impairment.MeasurementsParticipants completed annual assessments of depressive symptoms (15-item Geriatric Depression Scale). Average ambient PM_2.5 exposure at the residential location was estimated by spatiotemporal modeling for the 3-years preceding each neuropsychological assessment. Participants underwent separate annual examinations for incident dementia defined by DSM-IV. Latent-class mixture models examined the association between PM_2.5 and identified trajectories of symptoms.ResultsSix trajectories of depressive symptoms were identified. Across all women, PM_2.5 exposure was positively associated with depressive symptoms. The effect was especially strong in two clusters with sustained depressive symptoms (n = 625 sustained-mild [31%]; n = 125 sustained-moderate; [6%]). Among those with sustained-moderate symptoms, the estimated adverse effect of PM_2.5 exposure was greater than that of hypertension. Among women without dementia, associations were modestly attenuated.ConclusionLong-term exposure to ambient fine particles was associated with increased depressive symptoms among older women without prior depression or cognitive impairment.