Informal care outside the household by older people and cardiovascular health of caregivers: A Cross-Sectional Analysis of the SHARE European study.

Social isolation is an established cardiovascular risk factor, but the health implications of providing social support remain understudied. We examined whether informal care outside the household is associated with any self-reported cardiovascular disease. We conducted a cross-sectional analysis of 62,881 community-dwelling adults aged 50-84 from 28 countries (SHARE Wave 9, 2021-2022), using multivariable logistic regression with country fixed effects, clustered standard errors, E-values for unmeasured confounding, and sequential exclusions to probe reverse causality. The primary model adjusted for confounders only (age, sex, education, marital status, household wealth, and country); models additionally adjusting for potential mediators were treated as secondary. Among 16,178 informal carers (25.7%), the prevalence of any self-reported cardiovascular disease was 8.8% versus 12.8% in non-carers. In the confounder-adjusted model, informal care was associated with 15% lower odds of any self-reported cardiovascular disease (OR=0.85, 95% CI: 0.78-0.93; E-value 1.39 using the square-root odds-ratio-to-risk-ratio conversion appropriate for a common outcome, or 1.64 treating the odds ratio directly as a risk ratio, which overstates robustness). The association persisted after excluding care recipients and those with functional limitations, attenuated towards the null after excluding those in poor self-rated health, and was similar across age groups and sexes. Inference was robust to a pairs-cluster bootstrap and to population-averaged and random-intercept models, and to a weighted sensitivity analysis using SHARE calibrated weights (OR=0.78, 95% CI: 0.63-0.96).. Because the outcome reflects lifetime self-reported diagnoses and the design is cross-sectional, temporality cannot be established and the findings should be interpreted as hypothesis-generating. Informal care was consistently associated with lower prevalence of any self-reported cardiovascular disease and may be a marker of healthier cardiovascular ageing rather than a demonstrated cause of it.