Background

The aim of this study was to determine the gender-specific association of socio-economic status and obesity with the risk of metabolic syndrome (MetS) in the adult Korean population.

Methods

We used a national health examination data from a total of 8,606,008 individuals (males: 4,609,877, females: 3,996,131) with mean age 45.6±13.9 years from 2009 to 2015. Income level was categorized into 6 groups: Medical Aid beneficiaries and quintiles of income level in Health Insurance beneficiaries. MetS was defined according to diagnostic criteria of the National Cholesterol Education Program (modified NCEP ATPIII). Cox proportional hazard analysis were performed to evaluate the risk of MetS according to income level and obesity degree after adjusting for covariates.

Results

During 6 years of follow-up, 2,102,741 participants (males: 1,373,104, females: 729,637) diagnosed with MetS. High BMI was associated with higher risk of MetS in all income groups in both men and women.The risk of developing MetS in highest BMI level (≥35.0 kg/m2) was highest in Medical Aid beneficiaries in men (hazard ratio [HR]: 7.71, 95% CI: 6.10-9.73)) and was lowest in Medical Aid beneficiaries in women (HR:3.61, 95% CI: 2.63-4.94). In women, the risk of developing MetS in highest BMI level in the highest income group was lower than that in the lowest income group (HR: 4.74, 95% CI: 4.32-5.19 for Q1; HR: 5.66, 95% CI: 5.17-6.20 for Q2; HR: 4.51, 95% CI: 4.04-5.04 for Q5). However, the risk of developing MetS in highest BMI level in men according to the income level was not clear (HR: 3.83, 95% CI: 3.34-4.38 for Q1; HR: 4.41, 95% CI: 4.00-4.87 for Q2; HR: 4.19, 95% CI: 3.75-4.67 for Q5).

Conclusions

A positive association between obesity and MetS was lower in the high income group in women, suggesting that socioeconomic disparities might increase the risk of MetS development, especially in women.