Assessing the relationship between social deprivation and DNA methylation in a traumatic brain injury cohort

Health outcomes in human populations are strongly influenced by social, economic, and environmental factors known collectively as social determinants of health (SDH). Many of these factors are linked to the neighborhood in which a person lives, which has led to the development of measures such as the Social Deprivation Index (SDI) to characterize the level of social deprivation an individual is likely to experience based on where they live. One mechanism through which social deprivation may influence health outcomes is DNA methylation (DNAm). Research suggests that certain environmental exposures can cause localized changes in DNAm levels, which may influence specific health outcomes, as well as sweeping changes in global DNAm patterns, which may accelerate biological aging processes. The current project sought to investigate the relationship between social deprivation and DNAm levels in a cohort of adult traumatic brain injury (TBI) patients. Using patient zip code data as well as genome-wide DNAm data collected from the cerebrospinal fluid (CSF) of patients in this TBI cohort, we performed linear regression analyses comparing patient SDI to DNAm levels at specific sites in and around the BDNF gene as well as analyses comparing patient SDI to epigenetic age acceleration, which was calculated based on DNAm levels at multiple sites across the genome. Although previous research suggests that low socioeconomic status may contribute to increased methylation of BDNF, we found no significant association between SDI and DNAm of BDNF within the TBI cohort. However, our results did support a negative linear relationship between SDI and epigenetic age acceleration according to multiple epigenetic clock measures. Furthermore, stratifying participants by age revealed that this negative linear relationship was only found in participants 40 years and older. This project is significant to the field of public health because it contributes to the growing body of research on how epigenetic mechanisms like DNAm mediate the relationship between social deprivation and health outcomes. This research can help public health professionals better understand the causes of health disparities in this country and what policies and healthcare interventions can best address them