You may have heard this before, but if not, let us be the first to tell you. Your ZIP code, census area, or any other identifier of your precise location, is highly correlated with how long you end up living. There is a ton of variation in lifespan across United States neighborhoods, with a life expectancy of 56.9 years in one census area in West Virginia, while the average life expectancy in one North Carolina census tract is 97.5 years. That’s a massive difference for two groups of people in the same country, and especially in states that are not too far apart geographically.
Looking at the map of lifespan by census tract in the United States (Figure 1), a few things stand out to me. First, it comes as no surprise that the areas with the shortest life expectancy are concentrated in the southern states. We know that these areas generally have a lower average household income, and struggle disproportionately with chronic diseases such as obesity, diabetes, and hypertension. Another notable red spot on the map is in northeast Arizona, which is the location of the Navajo Nation. The Navajo, and Native Americans broadly, are known to suffer from very high rates of diabetes and other chronic diseases.
Figure 1: Life expectancy across census tracts in the United States (Source: CDC)
While these big picture takeaways aren’t particularly surprising, as we look closer, we see that these regions (the South, the Navajo Nation) aren’t alone. In fact, if you zoom in to any region on this map, you’re bound to find census tracts with higher than average life expectancy, as well as tracts with lower than average life expectancy. Take our home, the Bay Area, which overall has excellent life expectancy (Figure 2).
You’ll see that many of the census tracts are in the highest 20% by lifespan (dark blue), but there are also several that are in the lowest 20% (red). In the city of San Francisco, there are census tracts within half a mile of one another that have life expectancy differences of 20 years or more. We have massive discrepancies on a large scale (the South vs. the Northeast) and on a smaller scale (within the same city).
Figure 2: Life expectancy across census tracts in the San Francisco Bay Area (Source: CDC)
Why these discrepancies form and how to address them continues to be a hot topic, but some things are obvious. Differences in household income undeniably contribute to differences in lifespan, and if you look at a map of poverty in the United States, you’ll see a ton of overlap with the red areas representing shorter life expectancy. Income inequality is not the only answer, however.
It matters that a neighborhood is safe, not only to avoid death from violence or accidents, but also to encourage regular physical activity. Sticking with the importance of physical activity, things like parks and hiking trails actually do increase the health of the communities around them. Additionally, communities that are more suitable for walking and biking (rather than driving) can enhance physical activity and reduce rates of chronic disease.
Environmental health risks are a factor in many communities. Living near a major highway can lead to poor health outcomes, and this circumstance has been forced upon many marginalized communities. Nutrition is also a key factor, and many of the areas with the lowest life expectancy would also be classified as food deserts, meaning areas with low access to nutritious food.
There are too many factors for me to mention, but they all support the key takeaway which is that we’re a product of our environment. We spend a ton of time talking about individual behaviors, because it is possible to have a long healthy life while living in one of the census tracts in the bottom 20% by lifespan. Likewise, individual behaviors can lead to someone in a top 20% census tract having a shorter life than expected.
Nevertheless, there’s no denying that one’s circumstances have an enormous impact on their behaviors. We can talk all we want about getting 4 hours of Zone 2 exercise a week, but is that going to be possible for a single mother with no access to a gym or even a safe space to walk? We can talk about reaching protein targets and limiting refined carbohydrates, but we can’t control whether your block has a Whole Foods or a liquor store. Your health is what you make of it, but what you’re able to make of it has a lot to do with the community around you.
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