In her commentary on our article originally published in the Proceedings of the National Academy of Science (Goldman & Smith, 2002), Maitra discount the importance of factors related to self-management of disease and then claims that economic resources-in particular household wealth and health insurance- are the most important factors explaining the health education gradient (Maitra, 2010). We disagree. First, our paper is based on three complementary studies. The first involved a national probability sample of HIV-infected individuals (HCSUS) and examined patients receiving highly active antiretroviral therapy (HAART) and their adherence to that regimen. We demonstrated that the fraction using HAART, as well as the fraction adhering to the appropriate regimen, were both strongly related to schooling. For these two adherence measures, all education groups above high school were statistically different than the lowest education category. Finally, we found that both using HAART and effectively adhering to this treatment were associated with improvements in health status over time as measured by changes in general health status and CD4 cell counts per mm. Nowhere in their comment is the evidence from this study contested. The second—and by far our most important— study was a randomized prospective diabetes clinical trial (Diabetes Control and Complications Trial or DCCT). In this trial, diabetes patients were randomized to either an intensive or conventional therapy and followed through from the mid-1980s until 1993. Randomization is key since assignment to treatment was random by education groups allowing us to estimate differential impacts of enforced effective treatment across patients in different SES groups. DCCT was also our preferred diabetes study since it provided a far more objective health outcome measure—changes in glycosylated hemoglobin. At baseline of DDCT, the less educated were clearly engaging in worse adherence behavior (ie.the fraction missing an insulin injection among those with a high school degree or less was twice that of those with a post-graduate degree). The intensive therapy in DCCT included insulin injections three or more times daily or an external pump and were strictly enforced—patients were seen weekly at the clinic until a stable treatment program was achieved and then at least monthly. Telephone contact was made daily for the first week and weekly thereafter. Our results clearly showed that imposing intensive regime of adherence had a much larger impact on better health for less educated diabetic patients, and it is from this study that the title of our paper is derived. Being in the treatment group that had good adherence enforced on them eliminated 72% of the health outcome differences by education among these diabetics. Regardless of whether education's effect is causal or not, our paper shows that interventions to improve self-management will be more effective among the less-educated population and can also help reduce health disparities. As the DCCT trials shows, these can be achieved without providing health insurance to everyone (which does not improve adherence in our studies) or giving everyone an extra ‘dose’ of education. Analysis using randomized data is much less likely to be subject to various estimation biases stemming from non-random assignment or endogenity encountered in observational studies, including clinical heterogeneity. Our evidence from this DDCT study is not mentioned in this comment. The third study was a social science survey least well-suited to this task—namely, the Health and Retirement Study (HRS). The label least well suited is applied due both to the subjective health outcome measure, but mostly to the limited information available in the HRS on adherence. HRS diabetic respondents are asked at each wave whether they were taking medication that they swallowed and/or an insulin injection. Since there is no information available on episodes when medication is missed or injections are skipped, we could only use patterns available at the two year intervals of the survey, In spite of the admittedly limited data on adherence behavior, our analysis showed that poor treatment maintenance behavior was more common among the less educated and was negatively correlated with subsequent good health. While we would prefer the evidence in our paper be considered as a whole, Maitra's (2010) commentary only revisits the HRS observational diabetes study, so a more appropriate title might be “Can Patient Self-Management Explain the Health Gradient? One third of Goldman and Smith (2002) Revisited.” While we should not be giving new titles to comments on our work, we would like to hold Maitra to the same standard. The original title of our article was “Can Patient Self-Management Help Explain the Health Gradient?” and we have highlighted the omitted word in bold and italics. Since there was never a claim that adherence behavior was the sole explanation of the SES health gradient or for that matter even the most important, we are a bit puzzled by this comment since it also shows that adherence behavior, even when not well measured, does improve health.
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Sep 5, 2022
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