Does where you live affect your health?
Research has shown that neighborhoods with high socioeconomic deprivation also have higher mortality rates. But, those studies were a snapshot in time and did not consider how changes in socioeconomic deprivation—either positive or negative—corresponded to changes in health.
Most research also didn’t track subjects over time to determine if health outcomes improved when a person’s neighborhood conditions improved.
In a pair of new observational studies published in August and November in the journals American Journal of Epidemiology and Cancer, Qian Xiao, assistant professor of health and human physiology at the University of Iowa, tracked health outcomes among Americans who stayed in the same neighborhood for more than a decade. For the American Journal of Epidemiology, Xiao examined mortality rates for cardiovascular disease, cancer, and all causes generally. For Cancer, Xiao and postdoctoral researcher Dong Zhang studied rates of colorectal cancer specifically.
“The reason why we thought our study design is important was that previous studies only looked at conditions at one time point,” Xiao says. “People in lower socioeconomic status neighborhoods are more likely to die and more likely to get cancer. The next step would be, if you changed your neighborhood, would that have an impact on your health outcomes? That’s really the focus.”
Xiao says the studies supported her hypotheses—if the socioeconomic status of a neighborhood improves, mortality rates decline; however, if the status deteriorates, mortality rates rise. To measure socioeconomic status, Xiao says she looked at variables within neighborhoods such as household income, the number of people living beneath the poverty line, employment rate, and education levels, among other factors.
“If you improve neighborhood conditions—if a neighborhood is in an upward trajectory—we found that there is a lower mortality rate,” she says. “If a neighborhood has a downward trajectory, the death rate rises.”
In the colorectal cancer study, Xiao found that colorectal cancer rates increase as neighborhoods deteriorate. However, she says colorectal cancer rates did not improve when a neighborhood went from a low socioeconomic status to a higher level.
For the two studies, Xiao and her fellow researchers relied upon data from a 1995–96 National Institutes of Health-AARP study that surveyed people age 50 to 71 in California, Florida, Louisiana, New Jersey, North Carolina, and Pennsylvania, as well as Atlanta and Detroit. The researchers focused on study participants who remained within a kilometer of their address 10 years later. Neighborhoods were determined by census tracts and health outcomes were determined by the Social Security Administration Death Master File and cancer registry databases, according to the studies.
“Among various types of cancers, there has been more robust evidence suggesting that socioeconomic status plays an important role in colorectal cancer when compared to other cancers,” Xiao says of the reason for focusing on colorectal cancer. “It’s not the only cancer in which socioeconomic status plays a role, but one of them.”
In the mortality rate study, Xiao says researchers found that the scale of change in a neighborhood directly correlated to the overall degree of improvement in mortality rates.
“We did find that the higher the improvement was, the higher the reduction of mortality in general,” she says. “Also, the higher the increase in socioeconomic deprivation, we also find a higher increase in mortality rate. There seemed to be a trend there.”
The colorectal study yielded slightly different results, however. Xiao says neighborhoods that remained low or trended lower in terms of socioeconomic status had a higher risk of colorectal cancer.
“But we did not find any difference in people who lived in a neighborhood that moved from low to high socioeconomic status,” Xiao says. “Neighborhood improvement didn’t seem to do much here for colorectal cancer—not like for mortality rate.”
Because the studies are observational, Xiao says she cannot provide direct evidence that socioeconomic status changes health outcomes. However, she says she is hopeful that those interested in improving neighborhood conditions take the results of the studies into consideration.
“Both studies found that neighborhoods that are in a downward trajectory had adverse health outcomes and maybe that suggest we should be more aware of the risk there and monitor or study what mechanisms appear to drive those risks,” she says.
Also participating in the study published in the American Journal of Epidemiology were David Berrigan at the National Cancer Institute in Bethesda, Maryland; Tiffany M. Powell-Wiley at the National Heart, Lung, and Blood Institute in Bethesda, Maryland; and Charles E. Matthews of the National Cancer Institute. Participating in the colorectal cancer study were Matthews, Powell-Wiley, and Dong Zhang in the Department of Health and Human Physiology at the University of Iowa.
Source: University of Iowa
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