Evaluation of the association between mortality and economic status in patients with metabolic syndrome in Korea: a retrospective cohort study using the National Health Screening cohort.

Background The disease burden of metabolic syndrome (MetS) is increasing with increasing prevalence. Economic deprivation is a risk factor for MetS and contributes to the overall mortality. Therefore, this study aimed to investigate the association between economic status and mortality in patients with MetS.

Methods Overall, 83,786 patients with MetS were included from the Korean National Health Insurance Service-Health Screening Database. They were divided into three economic levels (low, medium, and high) based on the health insurance premiums charged according to the annual household income. Adjusted hazard ratios (HRs) with 95% confidence intervals (CIs) for all-cause mortality were calculated using Cox proportional hazards regression models.

Results The median follow-up duration was 10.0 years. Kaplan-Meier plots showed that the mortality rate was highest in males with a low economic status (P<0.001, log-rank test). Compared with that of the high economic status group, unadjusted HRs (95% CIs) of the middle and low economic status groups for all-cause mortality were 1.44 (1.32-1.57) and 1.88 (1.72-2.06), respectively, in males, and 0.84 (0.76-0.93) and 0.99 (0.89-1.10), respectively, in females. However, in the fully adjusted model, the corresponding HRs (95% CIs) were 1.23 (1.13-1.48) and 1.35 (1.23-1.48), respectively, in males and 1.17 (1.06-1.30) and 1.25 (1.12-1.39), respectively, in females.

Conclusion Among South Korean adults with MetS, the economically deprived population was significantly associated with higher mortality rates than those of wealthier groups.