Associations between air pollution and depressive symptoms in older adults: a repeated measurement study

Abstract

BACKGROUND AND AIM: Epidemiological studies concerning the relationships between different exposure windows of air pollution and symptoms of depression in older adults are limited. Hence, we investigate the relations between short-term and long-term exposure to ambient air pollution (PM10, O3, SO2, CO, and NOX) and depressive symptoms in a community-dwelling, free-living elderly population. METHODS: Study participants were in a multiple-wave representative sample (Taiwan Longitudinal Study on Aging, n=1956). In four surveys between 1996 and 2007, their depressive symptoms were assessed using the 10-itemed Center for Epidemiologic Studies Depression (CESD-10). We estimated air pollution from 1993 to 2007, including daily concentrations of five air pollutants from air quality monitoring stations, based on the administration zone of each participant’s residence. Generalized linear mixed models were applied to examine these associations after adjusting for covariates at different exposure windows (7-, 14-, 21-, 30-, 60-, 90-, 180-days, and 1-year moving averages). RESULTS:In one-pollutant model, the short-term and long-term exposure to CO and NOX were associated with increased risk of depressive symptoms; the ORs and 95% CIs for each 1 ppm increment in CO at 7-, 14-, 21-, 30-, 60-, 90-, 180-days, and 1-year moving averages were 2.23 (1.53, 3.27), 2.27 (1.63, 3.16), 2.19 (1.62, 2.96), 2.23 (1.62, 3.07), 2.12 (1.55, 2.90), 2.15 (1.55, 2.98), 2.14 (1.53, 2.99), 2.13 (1.56, 2.91), respectively. Moreover, for each 10 ppb increment in NOX at series exposure windows were 1.16 (1.08, 1.25), 1.18 (1.11, 1.26), 1.17 (1.11, 1.24), 1.18 (1.11, 1.25), 1.18 (1.11, 1.26), 1.18 (1.11, 1.26), 1.18 (1.11, 1.26), 1.18 (1.11, 1.26), respectively. In two-pollutant model, only the associations of exposure to NOX with depressive symptoms remained robust after adjustment for any other pollutant. CONCLUSIONS:Exposure to traffic-related air pollutants could increase the risk for depressive symptoms in older adults. KEYWORDS: air pollution, depressive symptoms, older adults, repeated measurement.