Joint effects of environmental and neighborhood socioeconomic factors on cognitive function in the Heinz Nixdorf Recall Study

Background: Modifiable physical and social environments are believed to influence cognitive health in older age. Objectives: To employ cutting-edge methods to analyze the impact of correlated environmental and socioeconomic neighborhood factors on cognitive function in German older participants. Methods: In the German Heinz Nixdorf Recall cohort study, participants underwent neuropsychological testing at the first follow-up examination (2006–2008) to derive a global cognitive score (GCS). Long-term exposure to air pollution was estimated by the land-use regression and chemistry transport models. Road traffic noise was assessed as outdoor weighted 24h and nighttime means. Seven neighborhood-level socioeconomic position (nSEP) characteristics were linked from administrative data. The joint effects of exposure combinations on GCS were estimated using two dimensionality reduction techniques: principal component (PC) analysis (PCA) and self-organizing maps (SOM). Results: Overall, 3748 individuals were included (median age 65 years; 50.7 % female). In single-exposure linear regression analysis, higher particle matter with aerodynamic diameter ≤2.5 μm (PM_2.5) and nitrogen oxides exposure, higher proportion of welfare recipients, and lower living area per resident were negatively associated with GCS. In the PCA, the first principal component (PC), the direction of maximum variance, was positively correlated with all disadvantageous nSEP factors and higher concentrations of all environmental exposures except ozone. This PC was associated with lower GCS. SOM revealed associations with lower GCS for 3 of 6 exposure clusters. These clusters were characterized by low nSEP (Cluster 1), high environmental exposure (Cluster 4) and high concentration of accumulation mode particle number concentration (Cluster 5). Discussion: We identified associations between distinct combinations of intercorrelated air pollution, road traffic noise, and nSEP disadvantages with poorer cognitive function, using two different dimensionality reduction methods. Our findings highlight the importance of considering combined environmental and social exposures to systematically assess the potential benefits of multimodal urban interventions aimed at mitigating these risk factors.