"Fundamental Causes" of Social Inequalities in Mortality

A Test of the Theory

Researchers have typically viewed socioeconomic status as a distal cause of mortality that is only the beginning of a chain of more causally relevant factors. However, historical patterns indicate a continuing link between socioeconomic status and mortality despite the mitigation or elimination of intervening factors. For example, after poor sanitation and overcrowding were essentially eliminated in developed countries as factors influencing disease and mortality, socioeconomic disparities in mortality remained strong. Two of the authors (Phelan and Link) previously argued that socioeconomic differences in mortality continue as new intervening mechanisms appear because individuals with higher socioeconomic status hold a wide range of resources that provide a health advantage. Among these are money, knowledge and power. These resources can be used to influence health outcomes through a variety of risk and protective mechanisms and are adaptable to changing health-related conditions. In this study the authors proposed to test this argument—that socioeconomic status is a “fundamental cause” of mortality—by examining mortality data for up to nine years from the National Longitudinal Mortality Study of 370,930 respondents to the Current Population Survey. The researchers hypothesized that the association of socioeconomic status and mortality would be stronger with more preventable causes of death (where socioeconomically-related resources would be useful) and less strong with less preventable causes.

Key Findings:

  • For high preventability causes of death, the differences in survival for different levels of socioeconomic status are much greater than for low preventability causes of death, supporting the authors' hypothesis.
  • Significant differences are found for each age group (25-44, 45-64, 65-99) and each socioeconomic status measure (education, family income) studied.