Association between socioeconomic position and transitions to multimorbidity involving major chronic diseases in Northwest Italy

Multimorbidity, the co-occurrence of multiple chronic conditions in individuals, complicates clinical management, increases healthcare use, and reduces life quality. This study investigates the association between socioeconomic position and multimorbidity, restricted to co-occurrence of two or more conditions among type 2 diabetes, cardiovascular diseases, selected cancers as a single category, chronic obstructive pulmonary disease, and depression, in a population-based cohort in Piedmont, Italy. A multimorbidity registry was built from 2013 to 2019, and diseases were identified through healthcare databases. Multistate models estimated the association between multimorbidity and socioeconomic position, stratifying by sex. Among 1,534,975 individuals, multimorbidity incidence was 1.31 (95% CI: 1.29-1.33) per 100,000 person-days. Lower SEP was associated with higher risk in almost all transitions to T2D and to CVD. In women, borderline significant associations were found from cancer to depression and from COPD to depression, comparing the lowest to the highest SEP. In men, significant associations were found for transitions to COPD as well as from COPD to cancer and from depression to cancer. Lower SEP was consistently associated with higher risks of single diseases and multimorbidity, with some sex-specific patterns. These findings highlight cumulative disadvantage and the need for policies targeting health inequalities in aging populations.