Atopic dermatitis (AD) is an inflammatory skin condition characterized by recurring flares of intensely itchy skin. It affects up to 17% of children and 10% of adults in the United States and carries a significant global burden as well. AD can cause sleep disturbances, behavioral issues, and social anxiety which can inflict psychosocial burdens on AD patients and their families in addition to the time and financial burden of caring for a chronic skin condition.
Risk factors for AD include genetic predisposition, skin barrier dysfunction, and environmental factors. Many studies have revealed differences in the prevalence, severity, and persistence of AD across racial and ethnic groups. In a recent review article, Croce, Levy, Adamson, and Matsui propose a framework for conceptualizing racial and ethnic disparities in AD.
Black and Latinx children are more likely to be diagnosed with AD and more likely to have severe and persistent AD, as compared to White children. This is despite the fact that the most well-described genetic risk factor for AD, mutation in the filaggrin gene, is less common in Black children than White children. Croce et al. point out that other biological variables which have been shown to vary across race exhibit conflicting data (as is the case for differences in transepidermal water loss, a biomarker which measures skin hydration) or can be influenced by someone’s environment (as is the case for differences in immunological phenotypes across race). Though more genetic risk factors might be discovered in the future, the lack of evidence supporting biological differences between groups points to the importance of contextual factors in explaining racial and ethnic differences in AD prevalence and severity.
Healthcare access, socioeconomic status (SES), and environmental exposures are three important factors which have been shown to influence AD prevalence and severity. Croce et al. point out that individual and structural racism have led to racial and ethnic disparities in all three of these areas, with minority groups generally experiencing less access to healthcare, lower SES, and more exposure to environmental risk factors. In their model, racism is the shared risk factor between Black and Latinx groups and its effect on AD prevalence, persistence, and severity is mediated through the variables of healthcare, SES, and the environment.
In addition to building a strong conceptual model for explaining AD disparities, Croce et al. identify numerous understudied research questions addressing the influence of different contextual factors on AD prevalence and severity. For example, no studies have addressed the impact of individual racism on AD, and many environmental factors which have been studied in other atopic diseases like asthma are understudied in AD including air pollution, indoor allergen exposure, and psychosocial stress. Though their review article focuses on Black and Latinx populations, racism and structural determinants of health may also explain why other racial and ethnic groups, such as Asian Americans, are disproportionately affected by AD.
This model could drive a paradigm shift in research on AD outcomes and interventions. Measuring and studying the ways in which structural and individual racism drive disparities in health care access, SES, and the environment could elucidate key risk factors for AD. Importantly, these disparities are treatable with various interventions including changes in individual attitudes, policy changes, and social justice. For example, a medical-legal partnership was used to identify and treat substandard housing conditions associated with childhood asthma. Interventions like this might reduce the incidence or severity of AD in populations with high risk of exposure to environmental triggers associated with AD development and flares, such as dust mites or mold.
Including contextual factors in clinical trial design could test whether certain treatments work better for certain populations. For example, a large-scale randomized control study in the United Kingdom found that daily application of emollient was not effective in preventing AD development in at-risk infants. At-risk infants were defined based on having a first-degree relative diagnosed with AD. Infants with specific contextual risk factors for AD, such as environmental exposures or reduced access to health care, might show a different level of benefit from this treatment or a community-based intervention targeting their specific risk factor. In summary, Croce et al. lay out a framework for understanding racial and ethnic disparities in AD which builds upon numerous studies across the biomedical and social sciences. Considering the high prevalence of AD and its substantial impact on quality of life, reducing disparities in AD will go a long way in promoting health equity, the attainment of the highest level of health for all people.