Educational disparities in health behaviors among patients with diabetes: the Translating Research Into Action for Diabetes (TRIAD) Study

Social disparities in health are well recognized, although the mechanisms that link lower socioeconomic status (SES) with poorer health outcomes are not fully understood [1, 2]. Poorly educated, impoverished and minority patients often have poorer access to and lower quality of medical care [3, 4]. However, social disparities in health have been reported even in populations with uniform access to care [5, 6], and thus alternative pathways should be considered. Educational attainment is the one aspect of SES which is usually established in early adulthood and stable over the life course, and is relatively easily ascertained. This paper focuses on educational disparities in diabetes-related health behaviors.

Unhealthy behaviors and psychological states (e.g., depression, hopelessness, anxiety) have been associated with poor childhood conditions, inadequate education, blue-collar employment and financial barriers [7]. Social epidemiologists Mirowsky and Ross have used the theory of human capital [8] to propose that education endows people with the means to become "effective" individuals, who gain control of their health by developing a healthy lifestyle, thus mediating the association between education and health. Moreover, effectiveness yields benefits that include prosperity (e.g., higher income among well educated) as well as social support, but also provides benefits that transcend both. The authors pose three ancillary hypotheses about how education promotes health [8]. The first hypothesis, the human capital theory of learned effectiveness, posits that education enables people to better merge otherwise unrelated behaviors into a unified healthy lifestyle [8]. Refutation of this theory requires that income fully mediates the education effect on health. The second hypothesis, the theory of personal control, posits that education facilitates a sense of control over one's life, and those who feel in control seek and act on information that may improve health [8]. The third hypothesis suggests that education-related family human capital is transmitted, i.e., educated parents inspire a healthy lifestyle in their offspring [8].

The associations between educational attainment and health behaviors are particularly important in diabetes, given the critical role of health behaviors, including diabetes self-management and health-related lifestyle [9‐15]. Studies in diabetic populations with uniform access to and quality of care (receiving managed care or socialized medicine) have reported persistent social disparities in glycemic control [16, 17], diabetes-related comorbidites [18‐20], and diabetes-related mortality [21], suggesting that factors other than health care access likely mediate the SES-diabetes health relationship. Using a sample of managed care patients with diabetes, we studied the cross-sectional relationship between educational attainment (our primary measure of SES) and smoking, physical activity, self-monitoring of blood glucose (SMBG), foot self-exam, and diabetes-related health-seeking behaviors. We have previously shown that these managed care settings provide uniform access to and quality of diabetes care across levels of SES [6], providing less confounded data on the relationship between SES and health behaviors.

We hypothesized an educational gradient in health behaviors and that better quality of care and provider communication would attenuate the gradient. To elucidate possible mechanisms through which education may influence health behaviors, we structured analyses to evaluate (directly or indirectly) Mirowsky and Ross' hypotheses.

This is the first large study of the relationship between educational attainment and multiple health behaviors among fully insured patients enrolled in a managed care setting. We found that even in managed care settings with uniform access to and quality of diabetes care across levels of SES [6], less education was associated with poorer health care behaviors among particularly high risk patients for whom these behaviors would be unquestionably indicated and recommended by their health care providers.

Alternative SES indicators yielded similar, although not always significant, findings. In general, education and income more strongly predicted health behaviors than social class or parental education. Each indicator has characteristics which influence its association with each outcome. Income varies over time and is likely to be influenced by adult health status, since progressing disease severity may reduce income. Educational attainment, on the other hand, is generally more stable over the life course, and less likely to be influenced by diabetes health status, since diabetes related complications typically occur later in the life course. Moreover, since education is a strong predictor of subsequent income, income may be considered as on the causal pathway between education and behaviors. Parental education may be less predictive of adult behavior given that childhood social exposures may be overshadowed by later life experiences and opportunities for social advancement. The Olin Wright social classification was only weakly associated with health behaviors in this study. This measure of social stratification is questionable among homemakers and the unemployed; furthermore, class may be a less pertinent social determinant of health in the United States than in Europe.

The observed relationships further our understanding of the poorer health outcomes persisting in lower SES patients with diabetes in managed care settings. The strong SES gradients in smoking and physical activity are consistent with other population-based studies including diabetic patients, although the SES indicators varied across studies [28, 29]. A population-based US study (Americans' Changing Lives Survey) reported that poor behavioral patterns failed to fully explained the greater all-cause mortality rates in lower SES individuals [30]. Although differences in model specification make the findings difficult to compare, a study of individuals from Finland, a country with socialized medicine, showed that the association between SES and mortality was practically eliminated by adjustment for health behaviors, biologic factors, and psychosocial factors [31]. Subjects with widely varying degrees of health coverage, access and quality are included in population-based studies in the U.S., while, like countries with socialized medicine, subjects in managed care settings such as in TRIAD, have relatively uniform access to care.

Mirowsky and Ross's theory of human capital [8] suggests that education improves health by allowing people to develop healthy lifestyles and prosperity (i.e., economic resources to buffer against illness and want). We found evidence that education has an independent effect on health behaviors in models adjusted for income. Moreover, education was predictive of a count of healthy behaviors, giving an indication of the degree of congruence of these health behaviors. Mirowsky and Ross's second hypothesis, the theory of personal control, suggests that education facilitates a sense of control over one's life, encouraging one to seek information that may improve health [8]. We found that education was strongly predictive of health-seeking activities in diabetes, and this was independent of income. The third theory suggests that educated parents practice and transmit a healthy lifestyle to their offspring. We found that parental education was modestly predictive of health-seeking behavior and regular exercise, although less strongly than SES indicators from mid- and later adult life.

Some study limitations and strengths should be considered. Our study analyses are based on self-reported education and health behaviors, and may be subject to some misclassification due to social desirability of some response options. The cross-sectional design precludes causal inferences. Although we found no significant interactions, the nonlinearity of logistic regression models limits our ability to detect significant interactions [32]. The Olin Wright classification applies only to currently employed subjects and led to exclusion of approximately 200 unemployed subjects who likely had lower SES. By creating indicators and proxies for childhood (parental education), mid-life (educational attainment) and late-life (income) socioeconomic status on health outcomes, we were able to consider a "life course approach [33]." While current health behaviors may reflect early SES influences over the life course and may have an accumulated impact [34], we find that health behaviors are more strongly associated with proximate social indicators than those from early life. Unfortunately, disentangling the separate and propagated effects of early-, mid- and late-life SES was not possible [35]. Additionally, we were unable to address potential mediators (particularly health literacy [36‐38]) that may explain observed social differences in behavior. Our sample came from the managed care populations participating in the 6-state TRIAD study. Findings may not apply to uninsured subjects given they would not be included in this sample. Thus our sample of subjects was not randomly selected from all people with diabetes in the United States, and our health plans may not represent the larger population of managed care settings. Our sample only included small numbers of subjects whose primary language was Spanish. It is important to note that our findings were observed in samples selected so that each examined health care behavior was unquestionably indicated as a beneficial, preventive measure (e.g., daily foot examination in diabetic patients with peripheral neuropathy, or a history of ulcers or amputations).

The need to improve health outcomes associated with diabetes has been a major focus in the United States in recent years. We find evidence of less frequent self care behaviors among particularly high risk, diabetic patients with less education and similar findings using alternative measures of socio-economic status. Our findings were consistent across demographic subgroups, and we did not find that better quality care or better health care provider communication attenuated educational disparities in health behaviors. Although the relationship between education and health behaviors was modest in strength for most behaviors, the cumulative effect of reduced practice of multiple self-care behaviors among less educated patients, over the course of diabetes, may have an important impact in shaping the social health gradient. Given the vulnerability of this population and the persistent social health disparities even in settings offering uniform care [5, 6], the effectiveness and benefits of targeted public health interventions that reduce barriers for and promote beneficial diabetes-related health behaviors in patients with less education should to be considered. However, because lower educational attainment is associated with poorer health, and poorer health can diminish patients' ability to practice beneficial health behaviors, we can not yet conclude from our findings that interventions aimed at improving health behaviors in disadvantaged patients will be effective in reducing social disparities in health.