Monthly Research Highlights
Phelan, Jo C., Bruce G. Link, and Parisa Tehranifar. “Social Conditions as Fundamental Causes of Health Inequalities: theory, Evidence, and Policy Implications.” Journal of Health and Social Behavior 51 (2010): 3-17
Socioeconomic condition is believed to be a “fundamental cause” of inequalities in health outcomes, as postulated by Link and Phelan, 2010. Socioeconomic status (SES) is defined in this context as a combination of money, power, knowledge, prestige and social network. This theory maintains that a gradient exists for the relationship between SES and certain diseases—as SES decreases, the risk for disease grows. To be “fundamental”, a cause must have four features: 1) the cause impacts more than one disease outcome and is not limited to only one health condition; 2) the cause impacts health outcomes through several risk factors; 3) resources can be used to minimize risks and consequences of the health condition after initial occurrence; and 4) the relationship between the cause and health condition(s) is replicated over time through replacement of “intervening mechanisms,” which are variables that mitigate the association between the disease cause and the disease. Support for the first feature comes from evidence that low SES relates to higher risk for death and disability from a range of chronic and infectious diseases. Evidence that multiple risk factors for disease, including obesity, low physical activity level, stress, and smoking status, are more common among individuals of low SES supports the second feature of the fundamental cause definition. The third feature is maintained by the fact that individuals with greater access to socioeconomic resources have a health advantage over those who do not in regards to diseases whose causes can be mitigated through access of those resources. For example, when the polio vaccine was first developed, only those with the most resources could access it. This resulted in a health inequity regarding which socioeconomic groups were affected by polio. When the vaccine was approved for widespread distribution to the entire U.S. population, the health differential lessened. Lastly, the final feature of a fundamental cause exists when advances in treatment and prevention directly impact the socioeconomic gradient of disease prevalence or mortality. For example, researchers Chang and Lauderdale (2009) discovered that higher SES individuals had higher cholesterol levels than low SES individuals, but the relationship between SES and cholesterol levels reversed when statins because widely used. The implication of this knowledge for health policymakers is to prioritize interventions that minimize the use of socioeconomic resources to improve health outcomes. Practice of this recommendation may contribute to the reduction of health inequalities between socioeconomic groups.
Neighborhood and Physical Environment
Diez Roux, Ana V., Sharon Stein Merkin, Donna Arnett, Lloyd Chambless, Mark Massing, F. Javier Nieto, Paul Sorlie, Moyses Szklo, Herman A. Tyroler, and Robert L. Watson. “Neighborhood of Residence and Incidence of Coronary Heart Disease.” New England Journal of Medicine 345.2 (2001): 99-106.
Physical and social features of the places in which individuals live can impact their health, independent of other factors. Diez Roux et al. (2001) utilized data from the Atherosclerosis Risk in Communities Study (ARIC) to conduct a prospective cohort study evaluating the relationship between neighborhood characteristics and incidence of coronary heart disease. A total of 13,009 individuals aged 45-64 were followed over a median of 9.1 years, starting between 1987 and 1989. Participants resided in one of four communities: Forsyth County, North Carolina; Jackson, Mississippi; suburban Minneapolis; or Washington County, Maryland. Residential neighborhoods were separated into three different categories based on an assigned socioeconomic score. Researchers analyzed risk of coronary events separately for black and white participants. Among whites, individuals who lived in the most disadvantaged neighborhoods had a statistically significantly greater risk of coronary events when compared to those who lived in the most advantaged neighborhoods, after controlling for age, study site, income, education, occupation, and other biomedical and behavioral risk factors. Among blacks, those living in disadvantaged neighborhoods also had a greater risk of coronary events than residents of more advantaged areas after controlling for the above factors, though this difference was of borderline significance. The implications of these results are that population health interventions should be designed with not only the individual in mind, but with the community infrastructure as well. Forces distal to individual behaviors are at play in influencing health outcomes of populations.