Original Contribution Systematic Assessment of the Correlations of Household Income With Infectious, Biochemical, Physiological, and Environmental Factors in the United States,

A fuller understanding of the social epidemiology of disease requires an extended description of the relationships between social factors and health indicators in a systematic manner. In the present study, we investigated the cor-relations between income and 330 indicators of physiological, biochemical, and environmental health in participants in the US National Health and Nutrition Examination Survey (NHANES) (1999–2006). We combined data from 3 survey waves (n = 249–23,649 for various indicators) to search for linear and nonlinear (quadratic) correlates of in-come, and we validated significant (P < 0.00015) correlations in an independent testing data set (n = 255–7,855). We validated 66 out of 330 factors, including infectious (e.g., hepatitis A), biochemical (e.g., carotenoids, high-density lipoprotein cholesterol), physiological (e.g., upper leg length), and environmental (e.g., lead, cotinine) mea-sures. We found only a modest amount of association modification by age, race/ethnicity, and gender, and there was no association modification for blacks. The present study is descriptive, not causal. We have shown in our sys-tematic investigation the crucial place income has in relation to health risk factors. Future research can use these correlations to better inform theory and studies of pathways to disease, as well as utilize these findings to under-stand when confounding by income is most likely to introduce bias. biomarkers; environment; income; nutrition; socioeconomics For the past century, results from studies in the Unite