<p>All-cause mortality by sex at 1, 3, and 5 years.</p>

Between-group differences were assessed using risk differences, Kaplan-Meier survival analysis, and Cox proportional hazards models, overall and across prespecified subgroups.</p> <p>Results</p><p>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.</p> <p>Conclusion</p><p>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.</p></div>