Education, wealth play different roles in health.

It is axiomatic that higher levels of education and wealth correlate with better health. Much research has shown that the more educated and wealthy people are, the more likely they are to be healthy. Very few researchers, however, have investigated the relative contributions of education and wealth to various health-related processes. Population Council demographer Zachary Zimmer and University of Michigan researcher James S. House collaborated on a study of the roles played by education and wealth in the onset and progression of ill health.

Americans' Changing Lives

The researchers used data collected in 1986 and 1994 from the more than 3,500 people aged 25 years or older who responded to the Americans' Changing Lives survey. In their research, Zimmer and House focused on answers to the survey question "How much are your daily activities limited in any way by your health or health-related problems?" On the basis of their answer to this question, people were classified as having no limitations or as having mild, moderate, or severe limitations.

The respondents' education was categorized as less than high school, completed high school, or more than high school. Education is an indicator of people's social and economic status in early adulthood and of their knowledge, skills, and capacities from that time on, all of which influence long-term patterns of exposure to and experience of risk factors.

Wealth was divided into personal incomes of less than US$10,000; $10,000-19,999; $20,000-39,999; or $40,000 or more. Income reflects socioeconomic position and resources closer to the time of the identification of the health problem. Income influences not only the exposure to or experiences of risk factors for disease, but also the resources available for the treatment or management of disease.

Because the survey was conducted in both 1986 and 1994, the researchers were able to explore the effects of education and wealth on both the onset of illness and its progression over time. They controlled for age, sex, race, and marital status, variables that can play a role in health outcomes.

Differing influences

The researchers found that education, which is typically completed by early adulthood, strongly influences when functional health problems arise. (Functional health problems are those that influence one's ability to conduct tasks that need to be completed on a daily basis.) But schooling had little or no effect on recovery or further decline, meaning the progression of such problems is not associated with education. Income affects the onset of functional health problems, and equally affects the course of such problems, especially the chances of improvement and avoidance of further decline.

In this longitudinal study, 542 deaths were recorded over time, and the researchers also looked at survival chances. Death is differentially influenced by education and income. Both factors correlated with improved survival chances among those who were healthy at the start of the survey. But, education had less influence on the risk of death among those who reported limitations at the start of the study.

Unexpected effects

"It is common in the fields of demography and public health to link education and wealth to health outcomes such as illness and death. But it turns out that the effects of education and wealth are not as straightforward as expected," explains Zimmer. "The fact that education does not alter the course of an illness once it arises may give us important clues about the mechanism of the effect of education." The researchers believe that education may improve health by giving people a better understanding of the nature of disease and how to avoid illness. Educated people may be more likely to exercise, eat healthily, and avoid smoking, for example. Hence, those with higher education may experience a delay or compression of illness compared to those with lower education. Illnesses that arrive later in life, however, may be severe and difficult to overcome.

Income is also important with respect to the prevention of illnesses, probably for similar reasons. High income, however, may additionally-help people recover from problems once they arise. Zimmer and House suggest that this may be the result of the greater ability, to treat and manage disease among those with higher income. "Higher current income," says Zimmer, "may allow people to purchase quality. health care and other amenities that can assist in recovery."

SOURCE

Zimmer, Zachary and James S. House. 2003 "Education, income, and functional limitation transitions among American adults: Contrasting onset and progression," International Journal of Epidemiology 32(6): 1089-1097.

OUTSIDE FUNDING

The National Institute on Aging and the Robert Wood Johnson Foundation