“A safe, decent, affordable apartment can act like a vaccine. It can keep you healthy now and in the future,” says Dr. Megan Sandel, a pediatrician and researcher at Boston Medical Center.

The safety, education norms and social networks of neighborhoods matter just as much as lead paint and leaky pipes. “That has huge implications for your income and ultimately your life expectancy,” Sandel says. “Your ZIP code may be more important to your health than your genetic code.”