OBJECTIVES: This study was conducted to clarify the relationship between lifestyle-related diseases and medical expenses after 10 years of metabolic syndrome. METHODS: The subjects of analysis were 2165 people who were randomly selected from a population insured by the government-managed health insurance. The test results of 1993 were used to divide the subjects of analysis into the following 4 groups, and the diseases and medical expenses of each group were examined for 2003. Group 1 had no abnormality in any of the four test RESULTS: BMI, blood pressure, lipid levels, and glucose metabolism. Group 2 was not obese but had abnormality in one or more of the other three tested categories. Group 3 was only obese or obese and had abnormality in one of the other three tested categories. Group 4 had metabolic syndrome. In this study, the lifestyle-related diseases were diabetes, hypertension, hyperlipidemia, cerebrovascular disease, and ischemic heart disease. RESULTS: The risk of each lifestyle-related disease was examined by odds ratio adjusted by sex and age in comparing Groups 2, 3, and 4 with Group 1. The odds ratios of Groups 2, 3, and 4 were higher than that of Group 1. In Group 4, there were significant differences in all diseases. Analysis of covariance adjusted for sex and age was performed, and medical expenses were compared between each group. As a result, the total amount of annual medical expenses in 2003 was 52,470 yen for Group 1, 82,120 yen for Group 2, 72,720 yen for Group 3, and 109,660 yen for Group 4. The medical expenses were significantly higher in Group 4 compared with Group 1. CONCLUSION: The risks of lifestyle-related disease and medical expenses of the metabolic syndrome are higher than that of non metabolic syndrome.