Age-specific change of prevalence of metabolic syndrome: longitudinal observation of large Japanese cohort.

To examine real age-related changes in the prevalence of metabolic syndrome, we studied longitudinal changes in the prevalence of metabolic syndrome in a single cohort of individuals. The participants included 112,960 Japanese (70,996 men, 14-94 years and 41,946 women, 17-85 years), who had received annual examinations between 1989 and 2004. Metabolic syndrome was defined according to the Japan Metabolic Syndrome Criteria Study Group and the US National Cholesterol Education Program (NCEP) guidelines. Overweight was defined as BMI>or=25 kg/m(2). Longitudinal changes indicated a birth cohort effect in the prevalence rate of metabolic syndrome with a lower or higher prevalence in the younger birth cohort than in the older for females or males, respectively. The estimation of the age-specific prevalence of metabolic syndrome demonstrated that in males, the prevalence of metabolic syndrome increased up to 50 decades of life for the Japanese and 60 decades of life for the NCEP criteria. In females, the prevalence increased with age up to 80 years old for both criteria. The estimated secular trends suggested that the prevalence rate of metabolic syndrome decreased in females and increased in males during study periods.