It's a Beautiful Day in the Neighborhood

If you live in the right zip code

This story is part of our ongoing series on the Social Determinants of Health, and where they connect and interact with the Developmental Origins of Health and Disease. Here we explore the social determinants of the built environment and how our environment influences our health. 
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A tale of two neighborhoods 
Neighborhood A wakes to the sound birds chirping. Neighborhood B wakes to the rumbling and honking of traffic. Kids in Neighborhood A walk to school on sidewalks through quiet neighborhoods. Kids in Neighborhood B navigate dangerous road crossings through traffic-filled streets to get to school. Neighborhood A has ample green spaces, parks and walking paths, while Neighborhood B is surrounded by fenced off lots, with nowhere for children to play. These neighborhoods are worlds apart, and yet only two miles from each other. 

Where we live is the framework for our lives. It defines our daily options, exposures, opportunities and connections. Our neighborhoods and physical environments are powerful health determinants. Where you live determines your access to fresh foods, clean air, educational and economic opportunities, and the quality of your schools and housing. These daily factors affect how long you live, and in some extreme cases, it can mean the difference of up to 30 years! Researchers call this the longevity gap, and it is linked to your zip code.  

At the intersection of your zip code and genetic code 
Your zip code is a better predictor of your health than your genetic code. This saying has been used more frequently over the past decade. Research backs it up. In and of themselves zip codes don't mean anything, but they are a rough measure for the wealth, environmental quality and social standing of a community. 

The demographic and wealth patterns we see today track very closely to a dark chapter in our country’s history, when redlining was used. The racially discriminatory housing and planning regulations of the 1930s and ‘40s were designed to segregate Black communities by making it impossible for them to buy homes in so-called “white” neighborhoods. Then, many Black communities were demolished and split apart by highways, as part of the federal interstate highway program. Today, three out of four formerly “redlined” neighborhoods continue to struggle. This translates into countless communities that are impacted by poverty, hunger, racism and pollution to this day.  

Severe, chronic stress  
The strong relationship between the quality of the physical environment and birth outcomes is well documented. Some examples:  

  • Living in an area with more vacant housing and property damage is associated with increased chances of having a pre-term or low birthweight baby.  

  • Women living in areas without a grocery store (food desert) are more likely to have a preterm birth.  

  • Mothers experiencing severe housing insecurity are at a very high risk of having low birthweight or preterm births. 

Developmental Origins of Health and Disease (DOHaD) research points to the reasons for these adverse birth outcomes: psychological, nutritional and environmental stress. The direct biological implications of stress on the next generation means the babies that are born early, or at a low birthweight, will be more susceptible to chronic disease later in their lives. This is at the root of the chronic disease epidemic we are witnessing today.  

The biology of stress 
Nature does have some built-in protections against stress, anxiety and emotional pain. For example, the placenta has the ability to chemically neutralize the stress hormone cortisol to its inactive form, called cortisone, in order to protect the developing fetus. However, this protective mechanism can get overwhelmed when a mother is experiencing extreme, ongoing stress. When this happens, cortisol makes its way through the placenta to the baby. Cortisol inhibits fetal growth, so even babies born at full term to highly stressed mothers can be small for their gestational age. Babies born at the low end of the birthweight scale have a higher risk for developing heart disease, type 2 diabetes, obesity and other diseases later in life. These risks are then passed on to their children, in an intergenerational cycle of risk.  

Addressing social inequity 
In order to address the epidemic of chronic disease in the U.S. we must go upstream, to the headwaters of the problem: the circumstances and places where people live, work, learn and gather. This is where access to the opportunities for health originate, and where we see the cumulative effects of policy, investment and support for individuals and families. We are all vulnerable to the biological effects of adversity. Addressing the underlying social, economic and environmental inequities in society is the key to solving the epidemic of chronic disease and creating healthier communities.