Social and environmental determinants of dementia risk: An umbrella review.

BackgroundGrowing evidence suggests that dementia risk is influenced not only by genetic factors but also by social and environmental determinants. Understanding these modifiable factors is critical for informing prevention strategies.ObjectiveTo synthesize existing evidence from systematic reviews on the associations between social and environmental determinants and the risk of dementia, including Alzheimer's disease, vascular dementia, and frontotemporal dementia.MethodsAn umbrella review was conducted by systematically searching five major databases for systematic reviews published between 2004 and 2024. Eligible reviews examined the relationship between at least one social or environmental determinant and dementia outcomes.ResultsThe review found strong associations between environmental exposures and increased dementia risk. Exposure to fine particulate matter (PM2.5) was consistently linked to elevated dementia risk, with estimates ranging from 3% to 226% per 10 μg/m3 increase. Occupational exposures to toxic metals, pesticides, and electromagnetic fields were also associated with higher neurodegeneration risk. Conversely, protective environmental factors included residential greenness and walkable neighborhoods. Among social determinants, higher education, socioeconomic status, and social engagement were found to promote cognitive resilience. In contrast, social disadvantage and limited access to healthcare contributed to increased dementia risk, likely through cumulative psychosocial stress.ConclusionsThis umbrella review underscores the significant role of social and environmental determinants in dementia risk. Targeted public health policies aimed at reducing environmental hazards and addressing social inequalities are essential for mitigating dementia risk and promoting cognitive health at the population level.