Multimorbidity, health service use, and health insurance by socioeconomic groups in 31 countries: a multi-cohort study

The prevalence of physical, psychological, and cognitive multimorbidity is marked by socioeconomic status (SES) inequalities. However, the relationship between multimorbidity patterns—particularly those involving cognitive conditions—and healthcare utilization, as well as the role of health insurance, remains poorly understood. This is the first study to explore healthcare-seeking behaviour among individuals with multimorbidity and assess whether these vary by SES and health insurance coverage. This multicohort study analyzed data from six longitudinal studies across 31 countries, including participants aged 50 years and older. Multimorbidity was defined as the coexistence of two or more disorders across physical, psychological, or cognitive disorders. Outpatient and inpatient healthcare utilization were measured. Random-effects logistic regression models were employed to assess associations with healthcare utilization, and random-effects Poisson regression models analyzed visit frequencies. Country-specific analyses were aggregated via multinational meta-analyses using random-effects models to generate overall effect sizes. We included a total of 1450209 individuals. Compared with individuals without any conditions, those with the most complex multimorbidity pattern had higher outpatient care utilization (OR 3.13, 95% CI [2.21–4.05]) but not as high as those with physical-psychological multimorbidity (OR 7.83, 95% CI [6.59–9.07]). Additionally, the association varied across socioeconomic groups, with lower SES individuals experiencing more pronounced disparities in care use. In contrast, the association between multimorbidity and inpatient care utilization was less pronounced. Health insurance coverage weakened the association between multimorbidity and outpatient care use, especially for individuals with physical-psychological-cognitive multimorbidity. Those with insurance had a stronger likelihood of utilizing outpatient care (OR 6.14, 95% CI [5.26, 7.16]) compared with those without insurance (OR 2.98, 95% CI [2.65, 3.36]). Cognitive disorders further complicate multimorbidity, indicating unmet healthcare needs, especially among individuals with lower SES. Our study highlights a potential role of health insurance in mitigating disparities in healthcare utilization related to multimorbidity.