Socioeconomic Disparities and Health: Identifying the Ways Education Plays a Role

Nancy E. Adler, Ph.D., is professor of medical psychology and director of the Center for Health and Community at the University of California, San Francisco School of Medicine. She is also vice chair of the Department of Psychiatry and director of the NIMH-funded training program in Psychology and Medicine there. Adler serves as chair of the John D. and Catherine T. MacArthur Research Network on Socioeconomic Status and Health.

Q. How did socioeconomic status become a focus of research on disparities in health outcomes?

A. There are many factors that have led to more research in the United States on the role socioeconomic status (SES) plays in health. Many researchers were intrigued and challenged by the findings from the Whitehall Study of British civil servants begun by Michael Marmot and colleagues in the 1980s.

This study indicated that health improved with increasing civil service status all the way to the highest occupational levels. This flew in the face of assumptions that effects of socioeconomic status on health were due solely to the adversities of poverty.

The study also made it clear that it was not possible to explain the relationship between civil service status (an indicator of socioeconomic status) through biology alone. The study prompted a lot of research on psychological and social influences on health and illness.

On a more personal level, my work was affected greatly by an observation made by Dr. Len Syme, who is emeritus professor of epidemiology at the University of California, Berkeley, at a meeting of health researchers. We asked him what he would want to know if he had to predict a person's health status.

His response was that he would need just one piece of information: The most powerful predictor of health status was SES, so this is what he would want to know. This comment helped me and others move from seeing SES as something that we needed to control for or adjust for in studies to seeing it as something that needed to be studied in its own right.

Q. What other effects did these factors have on research on SES and health?

A. One critical step was to find out whether the relationship between SES and health shown in the Whitehall studies existed in the United States also. We found that enough studies had been conducted looking at SES and health in the United States to demonstrate that socioeconomic status predicted health at all levels.

This means that there wasn't just a threshold of SES - such as poverty level - below which health was worse. Health improves as SES improves at all levels. Researchers had to start looking at the ways that SES might affect health, rather than simply seeing the issue as solely the effect of poverty. It also meant that it was time to become more serious about how we define SES.

Q. Isn't the definition of socioeconomic status fairly straightforward?

A. At one level, yes. Socioeconomic status encompasses education, income and occupation. These components have been treated like they are interchangeable by most researchers. Researchers in the United States have emphasized education. In British studies, occupation has been emphasized.

Q. What are the differences among the three factors?

A. All three components provide a certain place in the social structure, but each may bring different resources. An important task now, in the second generation of SES-health research, is to disentangle the effects of the different components and find out how and why they may operate in distinct ways to affect health. For example, it's important to be able to identify and understand what it is about education, and at what ages, that affects health. We need to know these pathways to be able to intervene effectively. (9)

Q. What pathways have been identified linking education to health?

A. Michael McGinnis and his colleagues (10) identified five factors that are known to affect health and have estimated the magnitude of the impact of each on premature mortality. SES affects four of the five factors: behavior, which accounts for about 40 percent of premature mortality; social circumstances, which account for about 15 percent; deficiencies in medical care, about 10 percent; and environmental exposures, about 5 percent. These determinants may overlap, but this gives some idea of order of magnitude of the effects of each factor and will help us disentangle the ways that education can affect health outcomes.

Q. What specific knowledge exists about education's relationship with these determinants?

A. Let's start with health behaviors, which include behaviors such as smoking, physical inactivity and a variety of other behaviors that affect health. The frequency of almost every health behavior differs by level of education. For example, the decline in smoking has been much steeper for college-educated individuals than for people with less education. As a result, we are beginning to see a relationship between education and lung cancer rates, with increases for individuals with less education.

Q.What about other pathways?

A. In terms of medical care deficiencies, the less educated experience a poorer quality of care. From the perspective of social circumstances and the social environment, education can provide access to many things. These include higher occupational status, a greater sense of control over your life and increased social support - all of which may affect a person's interactions with the health care system and choices they make.

Q. What are other health benefits of higher levels of education?

A. Education may make it possible to avoid stress and cope with stress better when it happens. In terms of environmental exposures, individuals with less education are more likely to have more hazardous jobs and, because they have less money, to live in areas where they are exposed to toxins (such as emissions from factories or freeways) and pathogens (disease-causing organisms). The focus in the environmental justice movement has been on unequal environmental exposure for poor and minority communities, but education plays a role in occupation and therefore in income.

Q. How do genetics fit in this picture?

A. Genetic predispositions are estimated to account for about 30 percent of premature mortality. There are several ways that genetics could play a role. One is that the same cluster of genes would lead both to education and to health, or there could be a genetically determined third factor - such as the ability to defer gratification or valuing a future time perspective - that predicts education and health.

These are theoretically possible, but there is no empirical data showing that either is true. It seems more likely that genetic vulnerability will play a role in determining which disease a person gets who is exposed to chronic stress or other adversities associated with lower education or SES.

Q. What possible alternate explanations are there for the relationship between SES and health?

A. One fairly frequently suggested alternative explanation is that illness causes decreases in income. The argument here is that health determines SES rather than SES determining health. Health can affect socioeconomic status, but this explanation is less convincing for education than it is for income. Education levels are set much earlier in life and tend to change less than income levels.

Q. What about the role of one's childhood health in determining future SES?

A. It is also possible that poor health during childhood can result in low educational attainment and compromise children's development, leading to lower SES in adulthood. Fortunately, the number of children with health conditions this serious is relatively small. Thus, while there will be some effect of health on education, the stronger effect is likely to be from education to health.

Q. What further study do you think will help advance our understanding of the effects of education on health?

A. We know that more education is better in terms of health. But we have to distinguish among cognitive or intellectual ability, gains in skills and capabilities, social networks and exposure to social norms, and credentials (for example, earning a high school diploma or a college diploma) as the result of education. The end results and policy implications are quite different for these.

Q. How does the quality of education factor in?

A. We also don't know very much about the role that plays. For example, do differences in the quality of education lead to differences in status? If they do, how do quality and status affect the relationship between education and health? Understanding education within the circumstances of our society in general is also very important.

Q. Where do you think research on education and health could lead?

A. I hope that research on education and health will lead to a consideration of education policy as health policy. The cost-benefit ratios for educational interventions may change substantially when health effects are factored in.

It's also important to think about education at all levels - from early childhood through adulthood. A lot of emphasis has been placed on early childhood education with good results, but we need better data to determine the relative impact of education at different levels (for example, interventions in early childhood education versus in secondary education).

Finally, if we take a global perspective, I think we'll see the highest reward-to-cost ratio if a serious investment is made in the education of mothers. In most parts of the developing world, this would mean educating young women.

Heart Smart: The Link Between Education and Cardiovascular Disease

Researchers have found associations between education and a number of specific diseases, with a connection for coronary heart disease particularly well documented. Rates of mortality from CHD decline with increasing levels of education (1) and education attainment has been linked to a number of biological and behavioral risk factors for CHD. (12)

In a large study of middle-aged women in the 1980s, Karen Matthews, Ph.D., of the University of Pittsburgh School of Medicine and colleagues found that women with lower levels of education were likely to also have a number of biological, psychological and social risk factors for CHD. These include higher systolic blood pressure, increased levels of LDL ("bad") cholesterol and lower levels of HDL ("good") cholesterol, and higher blood glucose and insulin levels.

Participants in the study with lower levels of education also reported more fat in their diets and were less likely to be physically active. They were also more likely to report that they smoked.

A lower level of education was also associated with higher levels of job dissatisfaction, higher levels of depressive symptoms, lower self-esteem and higher levels of anger. (12)

Dr. Matthews and her colleagues have also found that the incidence of aortic calcification (an indicator of cardiovascular disease) is related to education.

They have begun to examine how socioeconomic differences affect children's health at different ages. This work shows, for example, that lower SES is related to high blood pressure in childhood but not in adolescence, while physical inactivity is associated with lower SES in adolescence but not in childhood. (13) Matthews notes that children may start to develop unhealthy behaviors fairly early and that by adolescence, young people begin to show evidence of fibrous plaques, a type of damage to the arteries.

Matthews says these findings call for more study on the pathways that connect education and the risk of cardiovascular disease, and investigations of how the duration and quality of education improve cardiovascular disease risk at different stages of development.

Interview:

Education, Technology and Self-Management: Explaining the SES-Health Gradient

Dana P. Goldman, Ph.D., is director of health economics at RAND in Santa Monica, Calif., and an adjunct associate professor in the David Geffen School of Medicine and the School of Public Health at the University of California, Los Angeles. He received the 2002 National Institute for Health Care Management Research and Educational Foundation award for excellence in health policy.

Q. What is the SES-health gradient?

A. This is one of the most robust research findings in social science. However one measures socioeconomic status (SES) - usually by measuring income, education, or wealth - people with higher economic status have better health outcomes. So when we look at the population as a whole, we see that people at higher levels of SES appear to be in better health. This is true whether health is measured using mortality, general health, or other outcomes.

Q. How does medical technology affect the relationship between socioeconomic status and health?

A. New medical technology makes it possible for people to be healthy in ways that may have been considered almost unattainable in the past. New technology also tends to lower the price of health care. One example of this is highly active antiretroviral therapy (HAART) for the treatment of HIV. This treatment was not available in the 1990s. It may seem expensive in absolute terms, but it offers individuals the prospect of living - of making HIV a chronic disease rather than a disease that is inevitably fatal in the short term. That makes the cost of HAART therapy seem relatively low when measured as the cost per unit of health improvement.

Q. Who sees the health benefits of technology?

A. Individuals with more education are better able to comply with treatment and many new technologies make it possible for them to have better health. This is also true in the case of HAART, which involves a very complicated medication regimen. We've found that better adherence to the regimen is associated with higher levels of socioeconomic status.

From this perspective, new medical technologies can lead to bigger SES-related difference in health outcomes - there is a greater impact of SES than we might see with other types of medical care. People with higher SES tend to benefit more and earlier from certain types of new medical technologies. One way to think about this is to think of new medical technologies as a sale on health - people with higher SES are often situated to take advantage of the sale and are likely to benefit more.

Q. You refer to certain types of new medical technologies. Are there exceptions to this?

A. Yes, some medical technologies work the other way and tend to improve the health of individuals with lower SES. Examples of this include pharmaceuticals like the anti-hypertensives and beta blockers. These basically take the place of health behaviors, like improving one's diet, exercising and not smoking. The central issue is how medical technology interacts with patient behavior - this is what affects health outcomes.

Q. How does SES, or education in particular, affect the interaction between medical technology and patient behavior?

A. Education gives some benefit beyond that of income alone. Let's take the treatment of diabetes as an example. Current treatments for diabetes involve technologies such as oral medications, insulin injections or the use of an insulin pump that require a lot of self-management on the part of the patient. These include home monitoring of blood and glucose, changes in diet and exercise, and a range of other behaviors to help keep blood glucose under good control. From a purely health disparities perspective, these treatments are likely to offer more benefit to educated patients who are more likely to comply with fairly complex treatment regimens. (11)

On the other hand, a treatment for diabetes like a stem cell transplant that restores insulin-producing capabilities to the pancreas is likely to be neutral on education or SES, or to disproportionately benefit low-SES individuals because it does not require the same kind of patient self-management over the long haul.

Q. But certain types of educational interventions are also likely to lead to greater improvements in self-management for lower-SES individuals?

A. Yes, our research indicates that in diabetic patients randomized to intensive treatment or standard care, intensive monitoring has greater benefits for individuals with less education. (11) This was the case even when we looked at a population where all participants had at least a high school diploma and we measured education up to a postgraduate degree. These intensive treatment regimens led to better control of blood glucose levels for less educated participants in comparison to a control group following a common treatment regimen. We found that enforcing an intensive treatment regimen had a much larger impact on individuals with fewer years of education than on individuals with higher levels of education.

Q. Did the treatment itself lead to the improvement, or did patients change other behaviors that led to better control of their diabetes?

A. We found that there were not any significant differences between the treatment and control groups at any education level in behaviors such as smoking or vigorous exercise. So the improved health among less-educated individuals in the treatment group doesn't seem to be caused by changes in personal behaviors that are likely to lead to better health outcomes. Better adherence to a medically superior treatment regimen is what appears to have led to improved health.

Q. What is it about education that appears to affect patients' self-management behaviors?

A. We investigated the relationship between years of schooling, higher-level reasoning (as measured by the Wechsler Adult Intelligence Score) and poor self-maintenance behavior. We found that when the measure of higher-level reasoning was included, the effect of years of schooling disappeared. This suggests that the capacity for higher-level reasoning, rather than economic resources, may play an important role in patient self-management. (11)

Q. What conclusions can be drawn from your research?

A. Better-educated people are healthier, but our studies indicate that the SES gradient can be changed. This raises lots of questions about why education is important and how to modify the relationship between SES and health. Is higher-level reasoning a critical determinant of patients' abilities to self-manage their care? Is it possible to design treatment protocols that are based on the education level of the target population? Can findings from these studies be generalized to other diseases and conditions? Questions about how different medical technologies affect the SES-health gradient, and how medical technologies and education interact to produce health outcomes, also remain to be explored.

Definitions and Implications

Education may seem like a fairly straightforward concept, but there are many ways to think of education and many ways to measure it. The ways that education is measured in most studies are quite basic. Measurements typically include the number of years of education completed or whether a subject obtained a specific educational credential, such as a high school diploma or undergraduate degree.

To be able to answer questions about education's role in society and how it is related to health, more sophisticated measures of education - and its effects - are needed.

Education may cause changes in intellectual flexibility, leading to better skills in using and evaluating information. In a highly technical health and health care environment, this could mean that increasing the average level of education would also lead to improved population health.

Education may also act as a kind of super-resource - an avenue to achieve what is good and avoid what is bad in any particular social context. For instance, education leads to credentials and skills that provide access to prestige, jobs and money. On the negative side, disease may not be as avoidable among people who have lower levels of education. Education can also be viewed as a flexible resource. The pathways connecting education and health can change or go away, and new ones may emerge. The role of education, or of its different aspects, may also change or be different in relation to different health outcomes. (14)

Although there is some evidence that more education leads to better health, (7) most of the research on education and health is "correlational," indicating an association between the two factors, but not that either causes the other. Many possible explanations for the relationship between education and health are still being explored, with particular attention to the ways in which education or the experience of being educated is transformed or translated into specific health outcomes.

2. How does SES 'get under the skin'?

There are several ways that the process of education, or the level of education achieved, could affect health. Some of these involve education-related skills and their use specifically within health contexts. The process of becoming educated may lead to increases in the ability to understand and use complex information. Education may improve people's abilities to manage their own health - to comply with medical advice and to change behaviors that are bad for them. Education may also help individuals feel more confident about using the health care system.

Many of these skills are aspects of health literacy, (15) which has been defined in Healthy People 2010 as "the degree to which individuals have the capacity to obtain, process and understand basic health information and services needed to make appropriate health decisions."

The level of education completed or credentialing, in the form of a high school diploma or college degree, may also open doors to many benefits and resources that are associated with better health, including greater income and safer occupations.

One area of research that holds promise is examining the relationships among education, stress and health. Chronic stress has been shown to have a negative effect on health. (16) Recent research suggests that education may have a protective effect among adults who have a child being treated for pediatric cancer. Researchers found that parents with higher levels of education were less likely to experience the types of changes in immune functioning experienced by parents with lower levels of education. The processes or mechanisms by which education would trigger this protection have not been identified, however. (17)

Studies, primarily of rats and non-human primates, have also documented the changes in physiology and neurobiological development that can occur in very young animals experiencing early deprivation or other negative early experiences. (18,19) These studies, in combination, suggest that early experiences - including learning and education - might be reflected in biological and behavioral changes that affect health across the lifespan.

Resources

* For information about the Whitehall Study, contact:

Professor Michael Marmot
Department of Epidemiology & Public Health
University College London
1-19 Torrington Place
London WC1E 6BT, England
Tel: 44 171 391 1717
Fax: 44 171 813 0280
Michael@public-health.ucl.ac.uk
www.workhealth.org

* Health Canada-Santé Canada
Population Health Approach: What Determines Health: "What Makes Canadians Healthy or Unhealthy?"
[with underlying premises and evidence table]

The Research

Bibliography

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12. Matthews, K.A., Kelsey, S.F., Meilahn, E.N., Kuller, L.H., Wing, R.R. Educational attainment and behavioral and biologic risk factors for coronary heart disease in middle-aged women. American Journal of Epidemiology, 1989;129(6):1132-1144.

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