DNA methylation in context: Population patterns in social adversity and sensitivity to the health impact of air pollution

University Of Michigan At Ann Arbor, Ann Arbor MI

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Abstract

Inequalities in healthy aging are across racial groups are well-documented; the research literature on these inequalities in chronic conditions and cognitive impairment among older adults is growing. Neighborhood context has emerged as a potentially powerful determinant of these inequalities in aging-related health conditions, including cognitive decline, and may be a key intervention site. Neighborhoods include both social and environmental exposures important for healthy aging. Evidence indicates inequalities across racial groups in exposure to neighborhood social resources and air pollution. Pollution and aspects of social adversity are often correlated and may operate cumulatively to result in differences in healthy aging. Importantly, however, these chemical (i.e. pollution) and non-chemical (i.e., social adversity) stressors may act synergistically, whereby exposure to social adversity can heighten vulnerability to the harmful health impact of even low levels of pollution. Yet, the environmental and social science literatures – even the environmental and social epidemiology literatures – are largely separate. There is a pressing need to integrate the study of these exposures given their likely cumulative and synergistic effects on population health in order to direct effective interventions and policies. In addition to the gaps in our knowledge about the combined impact of chemical and non-chemical stressors on population patterns in healthy aging, there is a need to focus on outcomes that may serve as biological pathways to numerous diseases. Research on either pollution or social adversity has tended to focus on specific health outcomes. Focus on a single disease may underestimate the overall health impact of these exposures. It is critical to clarify the shared biological mechanisms that underlie numerous chronic diseases to understand the full impact of pollution and social adversity on population health. A growing literature points to the importance of epigenetic factors, particularly DNA methylation, linking socioenvironmental context to health. Indeed, it may be that epigenetic processes are an important mechanism through which both air pollution and social adversity are linked to population health. Our objective is to identify underlying DNA methylation mechanisms linking neighborhood social context and ambient and industrial air pollution and social adversity to measures of healthy aging. Clarifying the role of neighborhood in population patterns in health is critical, as neighborhoods are amenable to intervention. Identifying the role of DNA methylation patterns reflecting neighborhood context, including chemical and non-chemical stressors, can point to specific disease etiologies and causal mechanisms effective interventions to improve population healthy aging.