Impact of socioeconomic status on cardiometabolic multimorbidity progression trajectories: a multi-state model analysis based on three prospective cohort studies

Background: Cardiometabolic multimorbidity (CMM) has emerged as a persistent global health challenge, yet the role of socioeconomic status (SES) remains insufficiently elucidated. This study aims to investigate the associations between SES and both CMM progression trajectories and mortality risk. Methods: We harmonized data from three UKB, SHARE, and KLoSA. SES was defined based on income, education, and employment via latent class analysis. CMM was defined as the coexistence of two or more cardiometabolic diseases (CMDs), including type 2 diabetes (T2D), coronary artery disease, and stroke. First-onset cardiometabolic disease (FCMD) was defined as the initial manifestation within the spectrum of CMDs. Multi-state models and restricted mean survival time analyses were performed to explore potential underlying relationships. Results: This study included 387,665 UKB participants, 22,505 SHARE participants, and 8,357 KLoSA participants, with median follow-up times of 13.4, 17.3, and 16.0 years, respectively. Individuals with lower SES consistently had higher cumulative risks of disease progression and reached the equivalent 10-year cumulative risk much earlier. Low-SES individuals exhibited a 33.4% higher risk of developing FCMD and a 33.3% increased risk of progressing to CMM compared with the high-SES group. Notably, the strongest socioeconomic disparities in disease progression were observed for the transition from health to T2D (HR=1.45 [1.39-1.52]) and from stroke to CMM (HR=1.51 [1.19-1.93]). Low SES elevated the mortality risk following FCMD (HR=1.41 [1.30-1.54]), which was further exacerbated for transitions from stroke (HR=1.68 [0.95-2.96]) and CMM (HR=1.72 [1.41-2.09]) to death. Across all cohorts, a socioeconomic gradient was evident where disease progression and survival time declined with lower SES, with the onset of FCMD occurring 0.47 (0.16-0.79) years earlier and the progression to CMM occurring 0.76 (0.37-1.14) years earlier in low-SES participants compared to their high-SES counterparts. This trajectory culminated in a significant survival disparity after CMM diagnosis, where medium-SES and low-SES groups lived 1.39 (1.12-1.67) and 1.57 (0.73-2.41) years less, respectively. Conclusion: Significant SES disparities substantially accelerate CMM progression and mortality risk; this association has been consistently observed across populations in various countries. SES intervention strategies should be integrated into CMM assessments to mitigate the adverse health impacts of CMM progression on populations.