Socioeconomic status and morbidity: Are stress exposure, stress reactivity, or both the key mediators?

Abstract

Low socioeconomic status (SES) is robustly associated with higher risks of morbidity and early mortality. Two intermediate mechanisms—stress exposure and stress reactivity—have been proposed to explain this association. However, few studies have formally examined the mediation roles of these two processes in the SES-health link, particularly using a longitudinal design. This study, therefore, aimed to test the intermediate role of stress exposure (i.e., the total number of stressors, stress severity) and stress reactivity (i.e., emotional reactivity, stress appraisal) in contributing to SES disparities in morbidity over a 10-year period. Data were drawn from a subsample of 1,522 middle-aged and older adults (34-83 years of age, 57.2% female, 83.5% White) from the Midlife in the United States study, a nationally representative community sample. SES was assessed in 2003-2004. Stress exposure and stress reactivity were assessed using an 8-day daily stress assessment in 2004-2009. Morbidities (i.e., 26 chronic medical conditions) were assessed in 2003-2004 and 2013-2014. Participants from low socioeconomic status reported a faster increase in the total number of morbidities from 2003-2004 and 2013-2014 than their high-SES counterparts. Mediation analyses showed that the association between SES and morbidities was partially mediated by stress reactivity, or specifically, negative emotional reactivity, but not by stress exposure. These findings highlight the intermediate role of stress reactivity in contributing to SES disparities in morbidities, suggesting the importance of developing interventions focusing on strengthing stress reactivity to promote health in middle-aged and older US adults with low SES.