Researchers discover why living in a deprived neighborhood may raise dementia risk

Cambridge researchers have discovered why living in a disadvantaged neighborhood may be linked to an increase in an individual's risk of dementia.

In research published today, they show how it is associated with damage to brain vessels – which can affect cognition – and with poorer management of lifestyle factors known to increase the chances of developing dementia.

Dementia disproportionately affects people who live in socioeconomically disadvantaged neighborhoods. Individuals living in such areas show greater cognitive decline throughout their lives and higher dementia risk, regardless of their own socioeconomic status. Recent studies have also found that neighborhood deprivation is linked to differences in brain structure and greater signs of damage to brain tissue.

To explore this link further, researchers examined data from 585 healthy adults aged 40–59 living in the UK and Ireland who had been recruited to the PREVENT-Dementia programme. Details of the study are published in Alzheimer's & Dementia: The Journal of the Alzheimer's Association.

Among the data collected and examined were: neighborhood deprivation according to postcodes; cognitive performance assessed through a series of tests; modifiable lifestyle risk factors; and MRI brain scans to look for signs of damage to the brain's small blood vessels, which are crucial for delivering oxygen and nutrients to brain tissue.

The team found a strong link between living in a deprived neighborhood and poorer management of lifestyle factors known to increase the chances of developing dementia. In particular, people living in areas of high unemployment, low income and/or poor education and training opportunities were more likely to experience poor sleep, obesity and high blood pressure, and do less physical activity.

However, people living in deprived neighborhoods tended to consume less alcohol than those in less disadvantaged neighborhoods. Alcohol consumption is another known risk factor for dementia.

The researchers also found a significant link between cognition and neighborhood deprivation – particularly poorer housing and environment and higher levels of crime. This had the greatest impact on an individual's ability to process information quickly, their spatial awareness and attention.

One possible explanation for this comes from the team's finding that living in a deprived neighborhood was associated with damage to the brain's small blood vessels, which in turn affects thinking skills. Modifiable lifestyle habits are known to contribute to this damage, suggesting that the effect of deprivation on brain function – and hence performance in cognitive tests – may be down to lifestyle and vascular health.

Where someone lives can affect their brain health as early as midlife. It doesn't do this directly, but by making it more difficult for them to engage in positive lifestyle behaviors.

This means that people living in these areas may face more challenges in getting quality sleep and exercise, and in managing blood pressure and obesity. This can then have a knock-on effect on the health of blood vessels in the brain, leading to poorer cognition.

These lifestyle factors are no doubt influenced by both individual circumstances and the external environment in which they live. But importantly, the links we found were independent of educational attainment. So, even a person who has gone on to further or higher education and has a reasonably paid job may be better or worse at managing their lifestyle depending on where they live, perhaps due to better access to affordable healthy food options and safer recreational spaces."

Dr. Audrey Low, First Author, Department of Psychiatry at the University of Cambridge and Mayo Clinic, Minnesota

The researchers say their findings highlight the fact that dementia risk is influenced by environmental factors rather than just individual behaviors, and so reducing dementia risk will mean addressing the wider social determinants of brain health.

Senior author Professor John O'Brien, also from the Department of Psychiatry at Cambridge, said: "Where you live clearly plays an important role in your brain health and risk of dementia, putting people living in deprived neighborhoods at a serious disadvantage. This risk is preventable, but our works shows it's not enough to assume it's down to the individual. If we're serious about reducing health inequalities, it will require support from local and national policymakers."

The study highlights how different areas face their own challenges and hence will need different approaches, say the researchers. In wealthier areas, strategies could focus on reducing alcohol consumption, for example. Lower-income neighborhoods, on the other hand, may benefit from targeted campaigns promoting healthy lifestyles for dementia prevention. This will require policymakers and community leaders to tackle systemic barriers that are impeding individuals' abilities to adopt healthy lifestyle changes. This could include improving access to affordable healthcare and healthy food options, reducing crime, and providing safe recreational areas for exercise.

While these findings hold true for the UK and Ireland, the researchers say that more research is needed into whether they apply in other cultures. There is some previous evidence that the opposite is true in certain Asian cultures, for example.

The research was supported by the Alzheimer's Society, Alzheimer's Association, Race Against Dementia, Wellcome Trust, Alzheimer's Research UK and the National Institute for Health and Care Research Cambridge Biomedical Research Centre.