Neighborhood disadvantage linked to dementia risk in New Zealand population

People living in socioeconomically disadvantaged neighborhoods may have a higher risk of developing dementia, according to an NIA-funded study published in Alzheimer's & Dementia. Findings suggest that focusing dementia-prevention efforts on disadvantaged neighborhoods and encouraging health care providers to consider a patient's residential address could help reduce dementia risk.

Recent research has shown that individual behavioral changes, such as regular exercise, may help lower dementia risk. However, some neighborhoods where midlife and older adults live can limit their ability to make significant lifestyle changes. The environment in which a person resides also affects their exposure to other potential dementia risk factors, including pollution, noise, and extreme temperatures. Previous studies have explored the relationship between neighborhood characteristics and dementia risk, but results were mixed. To address the gap, a Duke University-led international team of researchers analyzed neighborhood disadvantage and dementia risk within New Zealand's population.

The researchers examined data from 1.41 million people using the New Zealand Integrated Data Infrastructure, which includes government, hospital, clinic, and pharmacy records. They calculated dementia rates based on diagnostic codes and dementia-related prescriptions. The level of neighborhood disadvantage was assessed using a score called the NZDep, which combines factors including income, unemployment, education, housing stability, and living conditions.

Analyses of this extensive dataset revealed that New Zealanders living in more disadvantaged neighborhoods in adulthood were more likely to develop dementia across the 20-year observation period. This association was most pronounced in disadvantaged neighborhoods, where the risk of developing dementia was more than 20% higher compared to the least disadvantaged areas.

The researchers aimed to determine whether individuals living in disadvantaged neighborhoods had increased dementia risk factors by midlife compared to those living in less disadvantaged areas. They examined data from the Dunedin Study, a long-term project following approximately 1,000 people born in 1972-1973 in Dunedin, New Zealand, tracking their health, behavior, and life circumstances from birth through adulthood. They found that by age 45, individuals from more disadvantaged neighborhoods had more dementia risk factors and scored lower on cognitive tests. These participants also faced more challenges with daily cognitive tasks, such as following conversations or remembering directions. MRI scans showed that, on average, their brain age appeared three years older than those from less disadvantaged areas, and they displayed more brain structure changes related to dementia.

The researchers found that this relationship between dementia risk factors and neighborhood disadvantage remained even after adjusting for individual socioeconomic factors. This suggests that the increased dementia risk associated with disadvantaged neighborhoods is not solely due to the socioeconomic status of the residents. Overall, the study suggests that disadvantaged neighborhoods have higher rates of dementia and that residents are more likely to have dementia-related risk factors, structural brain changes, and cognitive decline well before dementia is diagnosed. However, this study does not prove that neighborhood disadvantage causes dementia, and these results are not generally applicable to individuals in other countries. Nevertheless, these results indicate that neighborhood-level programs to reduce dementia risk factors, such as creating green spaces, are worth considering as a strategy in at-risk communities.

This research was supported in part by NIA grants R01AG032282, R01AG069939, R01AG049789, P30AG028716, P30AG034424, P30AG072958, and P30AG066582.

These activities relate to NIH's Alzheimer's and Related Dementias Research Implementation Milestone 1.I, "Identify risk factors across diverse populations."

Reference: Reuben A, et al. Dementia, dementia's risk factors and premorbid brain structure are concentrated in disadvantaged areas: National register and birth‐cohort geographic analyses. Alzheimer's & Dementia. 2024;20(5):3167-3178. doi: 10.1002/alz.13727.