Association between socioeconomic status and multimorbidity indices across 15 countries: a multi-regional cohort...

Multimorbidity poses a major threat to health systems. Given no internationally accepted definition of multimorbidity, little is known about multimorbidity burden worldwide and whether it varies across socioeconomic status (SES). We used individual-level data from four prospective cohorts between 2000 and 2022 to examine the association of SES with multimorbidity (measured by simple disease counts and four multimorbidity indices) using Cox proportional hazards models. Among 28 766 participants aged over 50 years, the incidence of multimorbidity ranged from 7.82 (95% confidence interval [CI] = 2.08-29.47) per 100 person-years to 29.01 (24.41-34.49) per 100 person-years. Low SES was related to an increased risk of multimorbidity, ranging from 5% (hazard ratio [HR] = 1.05; 95% CI = 1.00-1.11, defined by multimorbidity-weighted index) to 85% (HR = 1.85; 95% CI = 1.67-2.04, measured by simple disease counts), with a pooled HR of 1.04-1.27. Sociodemographic factors should be taken into consideration in multimorbidity prevention and management strategies.