Association of long-term air pollution and ambient noise with cognitive decline in the heinz nixdorf recall study

Little is known about the impact of long-term ambient air pollution (AP) and noise exposure on change in cognitive function over years in the elderly. In this study, we wanted to examine the association between long-term exposure to AP and noise with the rate of cognitive decline in a population aged 50 and older and susceptible groups with mild cognitive impairment or at a genetically higher risk of Alzheimer's disease (Apolipoprotein E ε4 positive). Participants in the German population-based Heinz Nixdorf Recall study carried out five neuropsychological tests. Individual tests scores at the first (T₁ = 2006–2008) and second (T₂ = 2011–2015) follow-up for each test were used as outcomes after standardization using predicted means adjusted for age and education. Global cognitive score (GCS) was defined as sum of five standardized scores of individual tests. Long-term exposures to particulate matter (PM₂.₅, PM₁₀, PM₂.₅ absorbance), accumulation mode particle number (PNₐcc), a proxy of ultrafine particles, and nitrogen dioxide were estimated by the land-use regression and chemistry transport models. Noise exposures were assessed as outdoor weighted nighttime road traffic noise (Lnight) means. We performed linear regression analyses adjusted for sex, age, individual and neighborhood socio-economic status, and lifestyle variables. Effect modification in vulnerable groups was estimated using multiplicative interaction terms between exposure and a modifier. Overall, 2554 participants (49.5% men, median age is 63 (IQR = 12)) were included. We found weak associations between higher exposure to PM₁₀ and PM₂.₅ with faster decline in the immediate verbal memory test. Adjustment for potential confounders and for co-exposures did not change the results. We saw no effects on GCS, and no effect of noise exposure. In susceptible groups, higher AP and noise exposure were tended to be associated with faster decline in GCS. Our results suggest that AP exposure may accelerate cognitive decline in older ages, particularly in susceptible groups.