Incidence of Metabolic Syndrome in Young Japanese Adults in a 6-Year Cohort Study: The Uguisudani Preventive Health Large-Scale Cohort Study (UPHLS).

To clarify the incidences of metabolic syndrome (MS) and risks in young Japanese adults by gender. A total of 58,901 adults who had undergone annual health check-ups in 2010 without a diagnosis of MS or missing data were divided into three age groups (20s through 40s) by gender. Participants were followed up for 6 years for new-onset MS according to Japanese criteria. The incidences of MS and risks were analyzed using the Cox proportional hazards model to adjust for confounding factors. The incidences of MS per 1,000 person-years were 2.2, 5.5, and 10.2 for women aged in their 20s, 30s, and 40s, respectively, and 26.3, 40.5, and 57.4 in the respective men groups. Compared with the group aged in their 40s, the hazard ratios of new MS were 0.19 (95% confidence interval [CI], 0.13-0.29) for women in their 20s and 0.50 (95% CI, 0.41-0.61) for women in their 30s, and 0.46 (95% CI, 0.42-0.50) and 0.70 (95% CI, 0.66-0.73) for men in their 20s and 30s, respectively, after adjustment for lifestyle factors. For women, MS was associated with smoking in their 20s and 30s, and eating speed in their 30s, and for men, was associated with physical activity, eating speed, alcohol intake in their 20s and 30s, and smoking in their 30s. Our findings suggest that the incidences of MS in the 20s and 30s are lower, but account for about 20-50% of women with MS and 50-70% of men with MS in their 40s. However, the data are not negligible and early lifestyle intervention for MS is necessary in young adults.