How Loneliness Gets Under the Skin: Inflammation Mediates the Relationship between Loneliness and Gait Speed

Abstract

Abstract Objective Loneliness is linked to interleukin-6 (IL-6), a marker of systemic inflammation, which chronically has deleterious effects on physical and mental health across the adult life span. This study investigated cross-sectional relationships among loneliness, IL-6, demographics, multimorbidity, depression, obesity, friendship quantity, and slowed gait. Methods Data from the MIDUS Biomarker Project, a national adult sample (N = 822, age range: 26-78 years) was used for this study. The PROCESS macro tested the hypothesis that IL-6 would mediate the relationship between loneliness and gait, after adjusting for demographic and health risk factors. Results Age (ß = .292, p < .001), sex (ß = .197, p < .001), body mass index (BMI: ß = .374, p < .001), waist-hip-ratio (ß = .242, p < .001), and loneliness (ß = .089, p = .025) but not multimorbidity (ß = .043, p = .20), depression history (ß = .022, p = .47), depression symptoms (ß = .036, p = .28), and number of friends (ß = .022, p = .46) contributed to the variance in IL-6. Serial mediation analyses supported the chained effect of loneliness on walking time through BMI and IL-6. Results also showed specific indirect effects of BMI and IL-6 on walking time, suggesting more than one pathway by which loneliness influences health. Conclusions These results suggest that loneliness may increase the risk of systemic inflammation, leading to slowed gait and adverse health outcomes. Psychosocial interventions that address loneliness may provide an optimal treatment target for reducing inflammation and preventing declines in health.