Loneliness in middle age and biomarkers of systemic inflammation: Findings from Midlife in the United States

Abstract Objective Middle-aged adults who are lonely have an elevated likelihood of death. Systemic inflammation may contribute to these increased odds. Using population-level data, this study tested if systemic inflammation is associated with loneliness in a broad age range of middle-aged adults in the United States. Methods This study used data from the Midlife in the US (MIDUS) survey Biomarker Project, which collected data on psychological, social, and physiological measures from a sample of middle-aged adults. This sample included the 927 participants who were 35–64 years at Biomarker Project data collection. MIDUS collected baseline data from 1995-1996 and a follow-up survey was conducted from 2004-2006. The baseline Milwaukee sample of African Americans was collected in 2005–2006 and the biomarker database was collected in 2004–2009. Biomarkers were obtained from a fasting blood sample. Self-reported loneliness was categorized as feeling lonely or not feeling lonely. Hierarchical regressions examined the association between biomarkers of systemic inflammation (interleukin-6, fibrinogen, C-reactive protein) and feeling lonely, adjusted for covariates. Results Twenty-nine percent of the sample reported feeling lonely most or some of the time. There was a positive significant relationship between loneliness and the three systemic inflammation biomarkers after controlling for covariates: interleukin-6 ( n  = 873) ( b [ se ] = 0.07 [0.03], p  = .014); fibrinogen ( n  = 867) ( b [ se ] = 18.24 [7.12], p  = .011); and C-reactive protein ( n  = 867) ( b [ se ] = 0.08 [0.04], p  = .035). Conclusions Feeling lonely is associated with systemic inflammation in middle-aged community-dwelling US adults.