Ambient air pollution and transportation noise : how they affect mental health in older adults

Abstract

Whether environmental factors are associated with mental health issues among older adults remains unclear. This doctoral thesis aimed to determine the extent to which air pollution and transportation noise affect mental health in older adults. We used data from the Swedish National study on Aging and Care-Kungsholmen (SNAC-K).

Study I PM2.5 was not linearly associated with faster cognitive decline over 12 years of follow-up. A significantly increased risk of faster cognitive decline was observed for low levels of PM2.5 (<8.6μg/m3) among the oldest-old group (OR 1.81; 95% CI: 1.02–3.22). The existence of cerebrovascular diseases further enlarged the risk.

Study II During follow-up, 15% of cognitively intact participants developed CIND, and 19% of cognitively impaired participants developed dementia. We observed 75%, 8%, and 18% increased risk of CIND onset corresponding to PM2.5, PM10 (both per 1μg/m3), and NOx (per 10μg/m3), respectively. Similarly, a higher hazard of progression from CIND to dementia was observed for exposure to higher levels of air pollution.

Study III Out of a total of 2812 participants, 137 initially depression-free participants were diagnosed with depression during follow-up. Exposure to higher levels of PM2.5 and PM10 (per 1μg/m3) and NOx (per 10μg/m3) were associated with 53% (HR 1.53; 95% CI: 1.22–1.93), 7% (HR 1.07; 95% CI: 0.98–1.18), and 26% (HR 1.26; 95% CI: 1.01–1.58) increased risk of depression, accordingly. Importantly, the hazardous effects of air pollution were attenuated among participants with high social activity.

Study IV A higher level of aircraft noise was associated with a faster annual rate of cognitive decline (β −0.007; 95% CI −0.012 to −0.001) over 16 years of follow-up. Higher levels of railway and aircraft noise exposure were associated with a 25% (HR 1.25; 95% CI 1.01–1.55) and 16% (HR 1.16; 95% CI: 0.91–1.49) higher hazard of developing CIND. However, no association was found between road traffic noise and cognitive outcomes.

Conclusions Long-term exposure to air pollution was associated with an increased risk of faster cognitive decline, cognitive impairment, and its progression to dementia, as well as depression incidence in older adults. Aircraft noise may be associated with worsening global cognition and cognitive impairment. Railway noise was associated with an increased risk of cognitive impairment. No evidence supported the relationship between road traffic noise and cognitive outcomes. These findings suggest air pollution and transportation noise may be risk factors impacting the mental well-being of older adults.