In a newly published study, researchers at the University of Wisconsin School of Medicine and Public Health report finding a correlation between living in neighborhoods with the fewest social and economic advantages and experiencing changes in brain structure and function that are characteristic of Alzheimer’s diseases and related dementias.
“Worldwide, dementia is a major cause of illness and a devastating diagnosis,” said study author Amy Kind, MD, PhD, professor of medicine in the University of Wisconsin School of Medicine and Public Health.
“There are currently no treatments to cure the disease, so identifying possible modifiable risk factors is important. Compelling evidence exists that the social, economic, cultural and physical conditions in which humans live may affect health. We wanted to determine if these neighborhood conditions increase the risk for the neurodegeneration and cognitive decline associated with the earliest stages of Alzheimer’s disease and dementia.”
The research was published in the journal Neurology. Scientists identified 601 people from two larger studies at UW of Wisconsin residents, the Wisconsin Registry for Alzheimer’s Prevention or WRAP and Wisconsin Alzheimer’s Disease Research Center clinical cohort.
Participants had an average age of 59 and no thinking or memory problems at the start of the study, although 69 percent had a family history of dementia. Most (85 percent) lived in Wisconsin. Study volunteers were followed for ten years to analyze changes in thinking, memory, and brain structure that are characteristic of early stage Alzheimer’s dementia. These data were correlated with qualities of participants’ residential neighborhoods while controlling for demographic factors such as race, sex, and age.
Participants had an initial MRI brain scan and then additional scans every three to five years. With each scan, researchers measured brain volume in areas of the brain linked to the development of Alzheimer’s dementia. Participants also took thinking and memory tests every two years, including tests that measured processing speed, mental flexibility and executive function.
Researchers used the residential address of each participant and a measure called the Area Deprivation Index to determine the neighborhood-level of disadvantage for each participant. Neighborhoods in the index are determined by Census block-group areas of 1,500 residents. The index ranks each neighborhood based on 17 indicators of disadvantage including income, employment, education and housing quality.
Of all participants, 19 lived in the 20 percent most disadvantaged neighborhoods in their state and 582 participants lived in the 80 percent of all other neighborhoods in their state. People in the first group were then matched one to four to people in the second group for race, sex, age and education and compared.
At the start of the study, there was no difference in brain volume between people living in the most disadvantaged neighborhoods and those in other neighborhoods. But at the end, researchers found more brain shrinkage in areas of the brain associated with dementia in people in the most disadvantaged neighborhoods. Researchers also found a higher rate of decline on tests that measure risk of Alzheimer’s disease.
“Our findings suggest that increased vigilance by healthcare providers for early signs of dementia may be particularly important in this vulnerable population,” said Kind.
“Some possible causes of these brain changes may include air pollution, lack of access to healthy food and healthcare as well as stressful life events. Further research into possible social and biological pathways may help physicians, researchers and policymakers identify effective avenues for prevention and intervention in Alzheimer’s disease and related dementia.”
Limitations of the study included a small number of participants from highly disadvantaged neighborhoods and a limited geographic setting. Future studies should involve larger and more diverse groups of people over longer periods of time.
The study was supported by the National Institute on Aging, the National Institute on Minority Health and Health Disparities and the University of Wisconsin Institute for Clinical and Translational Research.