BACKGROUND: Since the World Health Organization's pandemic declaration in March 2020, Korea has witnessed shifts in lifestyle behaviors, impacting habits tied to socioeconomic status and contributing to metabolic syndrome (MetS). To investigate this issue, the current study aimed to investigate changes in MetS prevalence, particularly based on income levels before and after the coronavirus disease 2019 (COVID-19) pandemic. METHODS: This study used data from the 8th Korea National Health and Nutrition Examination Survey (2019-2020). A total of 6,840 individuals aged 30-65 years were included in this study. Household income was divided into high (≥75th percentile), middle (25-75th percentile), and low (≤25th percentile). A multivariable logistic regression analysis was performed to explore the interaction between this association before and after the COVID-19 pandemic. RESULTS: A statistically significant difference was found in the prevalence of MetS before and after the COVID-19 pandemic (26.7% to 30.2%, P=0.001). These changes differed based on income levels. The increase in the prevalence of MetS was statistically significant in the low- and high-income groups but not in the middle-income group (low: 8.0%p increase [P=0.039], middle: 1.0%p increase [P=0.522], high: 6.4%p increase [P<
0.001]). The interaction between household income and the COVID-19 pandemic on MetS was statistically significant (P for interaction=0.032). CONCLUSION: This study revealed that P for interaction between household income, MetS, and the period before and after the COVID-19 pandemic was significant. Changes in physical activity and eating habits during the COVID-19 pandemic may have contributed to these differences.