Your neighborhood is an important place – it’s where your home is, of course, but also likely a source of socialization opportunities and a factor in where you shop, dine out, get your healthcare, etc. A recent study published in JAMA Neurology in January, 2020 found that your neighborhood can also play a role in the actual size of your brain, as well as the size of a very important structure called the hippocampus. The hippocampus is essentially your memory storage center; without it, you would not be able to form new memories about things that happen, people you meet, and what you do in a given day. The hippocampus is also typically one of the first brain regions to be affected by the tau tangles in Alzheimer's disease. This is why memory loss usually occurs as an early symptom for many people.
The study involved looking at about 950 cognitively normal individuals living in Wisconsin with a family history of dementia who were part of the Wisconsin Registry for Alzheimer’s Prevention (WRAP) or the Wisconsin Alzheimer’s Disease Research Center. The researchers created an index of how “disadvantaged” a neighborhood was (i.e. the poverty, educational level, income level, employment, and infrastructure within a geographic region), and also looked at cardiovascular disease risk. They then looked at magnetic resonance imaging (MRI) pictures of the brain for each individual to see if there was any relationship between the socioeconomic standing of people’s neighborhood and brain volumes.
The results found that people who lived in the most disadvantaged neighborhoods had approximately 4% lower hippocampal volume and 2% lower total brain tissue volume. This was true even after the researchers accounted for educational attainment, individual socioeconomic status, age, race/ethnicity, and sex. When cardiovascular risk factors were considered, these explained total brain volume differences, but could not account for the relationship between neighborhood and hippocampal volume.
Overall, the authors concluded that living in a very disadvantaged neighborhood is a separate risk factor for lower brain volumes. They speculated that there is an effect of the type of immediate community one lives in on overall brain volume during the aging process, especially on that critical memory storage area (the hippocampus). The broader implication of a study like this, that looks at how our environment affects our health, is to help to know where to target policies and interventions to try to improve overall health.
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What sort of community interventions can you think of that might help improve the quality of disadvantaged neighborhoods?