There’s a saying in public health that I can’t stop thinking about: your zip code might matter more than your genetic code. It sounds dramatic, but the data actually backs it up.

The Robert Wood Johnson Foundation has done a lot of work showing how much your neighborhood or environment around you affects how long you live. In one example often cited in these reports, two neighborhoods just a few train stops apart in the same city had life expectancies that differed by over a decade. Their research shows that where you live can strongly influence how long you live, sometimes by many years, because of differences in quality of life through things such as income, housing, food access, safety, and care.

Think about how interesting it is that a person’s environment in which they live can affect their life span by that much! Two people, born around the same time, maybe with similar genes, can have totally different life expectancies just based on the few miles between where they grew up. That gap isn’t about biology; rather, it is about the conditions of these locations and how they affect public health.

This is the clearest example I know of why health equity matters. Health equity basically means everyone having a fair shot at being healthy, no matter where they’re from. And right now, that fair shot isn’t equal at all. Some neighborhoods set people up to be healthy, and some set people up to struggle, before those people have made a single choice about their own health.

I’ve seen pieces of this myself. The kids I coached lived in communities with fewer resources than the ones I’ve been lucky to grow up around, and you could see how that shaped their options. It wasn’t about effort or willpower. It was about what their environment did or didn’t give them.

The reason this gives me a little hope, though, is that it’s changeable. Genes are hard to change or improve. Neighborhoods, food access, parks, clinics, and policies are not. If your zip code is shaping your health, then improving conditions within these various zip codes is one of the most powerful things public health can do.