To investigate the association between loneliness and all-cause mortality and inpatient hospitalisation among adults with atherosclerotic cardiovascular disease (ASCVD) in a real-world setting, and to explore the potential implications of routine loneliness screening. The primary hypothesis was that loneliness is associated with increased all-cause mortality.

Observational retrospective cohort study.

Analysis of linked administrative claims and routinely collected loneliness screening data from a large health plan.

7484 adult health plan members with documented ASCVD and ≥10 months of continuous enrolment around the screening date. Selection criteria included ASCVD diagnosis and sufficient enrolment for baseline assessment.

The primary outcome measure was 365-day all-cause mortality. The secondary outcome measure was the 365-day all-cause inpatient hospitalisation rate.

881 deaths occurred during follow-up (18% in the lonely group vs 11% in the non-lonely group). The lonely group had a lower proportion of men (54% vs 65%, p

Our findings corroborate the association between loneliness and morbidity and mortality among those with known ASCVD. The effect for loneliness was similar in magnitude to clinical comorbidities and smoking, suggesting that routine screening for loneliness may provide valuable information for assessing and managing the risk of death among patients with ASCVD.