Causes of Different Estimates of the Prevalence of Metabolic Syndrome in Korea

Background/Aims: Reports of the prevalence of and trends in metabolic syndrome in Korea have been inconsistent. Thus, we investigated the reasons underlying these inconsistencies. Methods: We estimated the prevalence of metabolic syndrome using different diagnostic criteria, exclusion criteria, and sampling weights among 5,509 respondents, aged 20-79, who participated in the 2001 Korean National Health and Nutrition Examination Surveys (KNHANES). Trends in metabolic syndrome were assessed by examining the 1998 (n = 6,747), 2001 (n = 4,337), and 2005 (n = 5,139) KNHANES. Results: The estimated prevalence of metabolic syndrome in 2001 ranged from 1.6 to 29.6% in males and from 10.1 to 32.8% in females, depending on the diagnostic criteria used. The exclusion criteria and sampling weights did not significantly affect the prevalence estimates. The prevalence of metabolic syndrome first significantly increased and then decreased between 1998, 2001, and 2005 in males (26.2, 29.6, and 27.2%, respectively) and females (29.2, 32.8, and 24.7%, respectively). Among the individual metabolic variables, triglyceride levels in 2001 were significantly higher than in 1998 and 2005, whereas other variables remained relatively constant during the same period. The exceptionally high triglyceride levels in 2001 might have contributed to the increased prevalence of metabolic syndrome between 1998 and 2001. Conclusions: Different diagnostic criteria for metabolic syndrome represent a major cause of the inconsistent estimates of prevalence, and the absence of standardized laboratory methods might have affected the trend estimates.