Background: Metabolic syndrome (MetS) is a major cause of increased cardiovascular disease mortality in middle-aged men. Previous studies examined the birth season and health status such as obesity and cardiovascular mortality in adulthood. However, the relationship between birth season and MetS has not yet been studied. In this study, we examined the prevalence of MetS in middle-aged men according to birth season. Materials and Methods: In this cross-sectional study, the data were collected from 4575 middle-aged men 30-50 years of age, who underwent a comprehensive health checkup examination. The subjects were separated into four seasons according to birth month. Results: There were no statistically significant differences in age according to birth season. However, there was a significant difference in the prevalence of MetS according to birth season: it was highest in spring (25.9%) and lowest in autumn (21.7%, odds ratio [OR] 0.787, 95% confidence interval [CI] 0.646-0.960, P = 0.001). Middle-aged men born in the spring had the highest body mass index (BMI) and prevalence of high waist circumference (WC), high fasting plasma glucose (FPG), and high blood pressure (BP), while those born in autumn had the lowest BMI (η2 = 0.007, P = 0.001) and prevalence of high WC (OR = 0.664, 95% CI 0.558-0.790, P = 0001), high FPG (OR = 0.761, 95% CI 0.624-0.928, P = 0.03), and high BP (OR = 0.633, 95% CI 0.531-0.755, P = 0.001). The prevalence of MetS according to birth months was highest in March (26.8%) and lowest in July (18.6%, OR 0.629, 95% CI 0.444-0.980, P = 0.001). Conclusion: Middle-aged men born in the spring had a higher prevalence of MetS than those born in the fall.
Keywords: birth season; metabolic syndrome; obesity; prevalence.