Social Isolation and Loneliness Across the Cardiovascular Disease Spectrum: A Narrative Review of Evidence, Mechanisms, and Clinical Implications

Social isolation is the objective paucity of social ties; loneliness is the subjective distress of relationships falling short of what one desires. Both are common, affecting roughly a quarter to a third of older adults, and both have cardiovascular consequences through several mechanisms, with some estimates suggesting an increase of 29% in coronary heart disease risk and 21-23% in heart failure hospitalization. We review the evidence for social isolation and loneliness' impact on cardiovascular disease separately for ischemic heart disease, heart failure, arrhythmia and sudden cardiac death, and stress- and substance-related cardiomyopathies. We also highlight plausible mechanisms by which social isolation and loneliness are linked to downstream adverse cardiovascular events, limitations with existing evidence, societal guidance, and policy frameworks currently aimed at addressing them. The evidence is densest for ischemic heart disease, though the largest cohort shows a 43% excess risk of myocardial infarction attenuating by approximately 84% to nonsignificance after full adjustment, and Mendelian randomization estimates a far smaller effect. The prognostic signal is more consistent than the etiologic one, with low functional social support carrying a pooled hazard ratio of 1.59 in established coronary disease. In heart failure, objective isolation rather than loneliness predicts post-diagnosis mortality, mainly in women, consistent with a self-care-dependent behavioral pathway.