Loneliness and all-cause mortality in the United States

Importance Loneliness affects more than half of US adults and has been declared a public health epidemic, yet whether clinically documented loneliness independently predicts mortality across diverse populations remains unclear. Objective To examine the association between clinically documented loneliness and all-cause mortality at 1, 3, and 5 years, overall and by sex, race and ethnicity, and age. Methods We conducted a propensity score–matched retrospective cohort study using the TriNetX US Collaborative Network, comprising electronic health record data from 65 health care organizations. Adults aged 18–90 years with at least one clinical encounter between January 1, 2016, and December 31, 2022, were eligible. Patients with a clinically documented diagnosis of loneliness were matched 1:1 (n = 28,944 per group) on age, sex, race and ethnicity, and 12 comorbidity domains to comparison patients with outpatient engagement and no loneliness diagnosis. The primary outcome was all-cause mortality at 1, 3, and 5 years. Between-group differences were assessed using risk differences, Kaplan-Meier survival analysis, and Cox proportional hazards models, overall and across prespecified subgroups. Results Among 57,888 matched adults (mean age, 55.4 years; 62.9% female), loneliness was associated with increased mortality at every horizon: 1-year hazard ratio (HR), 1.52 (95% CI, 1.40–1.66); 3-year HR, 1.35 (95% CI, 1.27–1.43); and 5-year HR, 1.29 (95% CI, 1.22–1.35). Absolute survival gaps widened from 1.57 to 2.82 percentage points. The largest 1-year relative excess occurred among male patients (HR, 1.85) and Hispanic patients (risk ratio, 2.33). Black patients had the greatest 3-year absolute gap (2.49 percentage points). Working-age adults showed sustained excess hazard across all windows (HR, 1.34–1.42), whereas older adults had the largest 1-year absolute gap (2.28 percentage points) with convergence by 5 years. Conclusion Clinically documented loneliness was independently associated with increased all-cause mortality at 1, 3, and 5 years, with the burden varying by sex, race and ethnicity, and age. These findings identify loneliness as a measurable, independent mortality risk marker and suggest that routine screening and targeted psychosocial intervention warrant prospective evaluation.