Pain mediates the association between psychological distress and increases in inflammation in middle-aged and older rural adults: A longitudinal cohort study.

Rural populations are under-represented in empirical studies testing associations between psychological distress, pain, and inflammation, despite known health disparities between rural and urban areas. This study examined associations between psychological distress symptoms and change in the inflammatory marker C-reactive protein (CRP), whether pain and functional limitations accounted for this association, and whether observed patterns varied among urban or rural adults. Participants were middle-aged and older adults (N = 5766; mean age = 52.98, SD = 8.64; 52.3% women) from the Korean Genome and Epidemiology Study (KoGES) community-based cohort, who completed survey questionnaires and a clinical visit biannually from 2005 to 2012. Linear regression, mediation, and moderated mediation analyses were conducted using data from waves 3 to 5, with CRP at wave 3 controlled as a covariate to model change in CRP. Rural adults had lower socioeconomic status, higher psychological distress, more functional limitations, and higher pain and CRP levels than their urban counterparts. Psychological distress at wave 3 was not directly associated with change in CRP (W3 to W5) after adjusting for demographic and health-related covariates including baseline CRP. However, moderation by residential areas was observed: Specifically, pain and functional limitations at wave 5 mediated the association between psychological distress at wave 3 and change in CRP only among rural adults (indirect effect = .003, p = .04). Findings provide preliminary evidence of the importance of addressing psychological distress in pain and systemic inflammation-related health conditions in adults who live in rural areas.