Socioeconomic gradients in health

Social scientists have examined the associations between social class and health. In general, wealthy people are found to live longer on average than middle-class people, and middle-class people live longer than poor people, but not longer than rich people. One researcher referred to this gradient as the “status syndrome”. This concept can be illustrated using an example of a short ride on the Washington DC subway. From the southeast of downtown DC to Montgomery County, Maryland, for each mile traveled, life expectancy rises by about 1.5 years. At this rate, a twenty-year gap would exist between poor Blacks at one end of the journey and rich Whites at the other.

The US Panel Study of Income Dynamics (Study 1) used a sample of 8,500 men and women who were followed for a twenty-year period, 1972-1991, or until they died. The study examined the risk of dying (in the twenty-year period) to average household income. Table 1 shows the risk of death in each group relative to the best-off group (those with incomes of 70k or more were arbitrarily a risk of dying of 1, and all other groups were compared with them). Two genders were combined, and the differences between income groups such as differences in age, sex, race, family size, and time period are taken into account. For example, in the 20-30k income group, 2.21 means that they have a 2.21 relative risk of dying indicating that they were 121% more likely to die in the twenty-year period compared to the richest group.

This relationship between income and health has shown to be true even in countries where everyone has access to health care, and when comparing those who have similar rates of smoking, obesity, and alcohol use. Now, let’s say that hypothetically, a second group of researchers used the same data and adjusted for an additional variable related to a person’s socioeconomic status--educational attainment. Hypothetical Study 2 attempts to see whether the effect of income on mortality would change when controlling for a person’s education level. The results are shown in Table 2.

Sources: Adapted from M. Marmot, “The Status Syndrome: How Social Standing Affects Our Health and Longevity.” Copyright 2004. Owl Books.