American Journal of Medicine, internal medicine, medicine, health, healthy lifestyles, cancer, heart disease, drugs

Social Determinants of Treatment Response

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Socioeconomic status is consistently linked to population health and specifically to the finding that there is decreasing health associated with decreasing social position. Despite the substantial literature, an analogous literature that is focused on clinical practice, and especially consideration of the individual, is almost nonexistent. Even in the absence of these data, physicians routinely incorporate patient life experience (biography) into their estimation of a patient’s clinical trajectory (prognosis) and when making therapeutic decisions. Some advances have occurred that strengthen the evidence base, such as the US Food and Drug Administration decision to show all results from randomized controlled trials on newly approved drugs by age, sex, and race. In this article we review the current status of research on the impact of social determinants of treatment response and illustrate the important role of the therapeutic context in both research and practice. Examples are provided in which a patient’s “biography” alters treatment response in subgroups of the population studied. We also provide examples in which multi-omic data and biographical information in a single individual can illuminate the clinical expression of disease. Finally, we suggest a research agenda that would better support physicians who use social and behavioral features as important elements in their decision making in clinical care.

Socioeconomic status, typically measured as income, educational attainment, or rank in an occupational hierarchy, is consistently linked to population health. Perhaps the most striking aspect of this relationship is the consistent finding of a gradient, not simply a threshold at the poverty line, with decreasing health associated with decreasing social position. Over time this link between socioeconomic status and health was broadened to include other social conditions, and the term “social determinants of health” was introduced to indicate the importance of the social environment, behavioral factors, and life experiences on population health.

Despite the substantial attention paid to social determinants at the population level, an analogous literature tuned to clinical practice and, of necessity, consideration of the individual patient, is almost nonexistent. Similarly, research on social determinants of health focuses primarily on risk for disease rather than also seeking to understand the way that social determinants relate to treatment response. These gaps are surprising because physicians routinely recognize how much a patient’s life experience (biography) affects both the clinical trajectory of a disease and its influence on response to treatment. For the purpose of discussing the role of social determinants at the individual level, we expand on traditional treatment outcomes (such as death and major morbidity) by considering the changes in specific clinical measures of treatment response (such as blood pressure, chest pain, or social/behavioral functioning) that are monitored as part of clinical care.

In this article we briefly review the current state of research on population-level social determinants of health and their impact on treatment response for the individual patient. We emphasize the importance of generating evidence to support empirically based statements about social determinants of treatment response that are applicable to diverse categories of patients. Such social determinants would be described via combinations of psychosocial and behavioral conditions and the patient’s social environment, some or all of which can be changing over the patient’s clinical course.

Social Determinants of Treatment Response: Population Subgroups

Physicians are aware that factors that influence risk for developing disease may be different from the risk factors of subsequent outcomes after the disease has occurred. For instance, hypertension and elevated blood lipids are both important risk factors for myocardial infarction. Once a myocardial infarction has occurred, however, pump failure, recurrent ischemia, and arrhythmias are more important predictors of the outcomes of myocardial infarction. Similarly, social determinants of health may have a different impact in response to disease treatment than in risk for population health outcomes (eg, disease incidence and risk of death and major morbidity). To date, the study of social determinants of treatment response has primarily been limited to demographic measures, such as age, sex, marital status, and race, or single social environment variables, such as socioeconomic deprivation or exposure to adverse events in childhood. In a first move toward the needs of clinical practice, the US Food and Drug Administration (FDA) 2012 Safety and Innovation Act has Congress instructing the FDA to provide the results of clinical trials by the demographic indicators of age, sex, and race. The FDA website now provides those results in a “snapshot” table for all new molecular entities and original biologics. Although clearly limited, these analyses may still influence clinical practice. For instance, even when treatment effects themselves do not vary by age, higher rates of outcome events in older patients may suggest a greater absolute benefit that changes the threshold for clinical action.

As many studies show the influence of biographical details on treatment response for selected subgroups of patients, the question arises as to why these differences exist. For example, it has been suggested that socioeconomic deprivation compromises the host response to tumors via poor nutrition or ongoing inflammation. Without a robust immune response, these patients are at risk for occult micro-metastases that are not detected during initial screening.123 The neurologic effects of depression may be different for those with and without a history of adverse childhood experiences. The subgroup of patients with depression and adverse childhood experiences may have reduced hippocampal volume and therefore exhibit a different neurologic presentation and treatment response.4 Different approaches to patient pain management may influence muscle strength and impact pain after lumbar disc surgery. Avoiding postsurgical activity might decondition the trunk and weaken back muscles, causing increased pain during normal activities.5 Understanding the reasons for these differences in treatment response is important in being able to target interventions toward restricted classes of patients.

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-Catherine Bachur, BA, Burton Singer, PhD, Allison Hayes-Conroy, PhD, Ralph I. Horwitz, MD, MACP

This article originally appeared in the May issue  of The American Journal of Medicine.

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