Seasonal variation in metabolic syndrome prevalence.

Accumulating evidence has shown that seasonal variations can exist within metabolic syndrome parameters. The aim of this study was to examine the hypothesis that there are seasonal variations in the prevalence of metabolic syndrome in Japanese subjects. We investigated a total of 1202 male workers in our institution (44+/-10 years) who underwent health checkups in both June (summer) and December (winter) 2008. In this study, metabolic syndrome was defined according to the criteria proposed by the National Cholesterol Education Program (NCEP), the International Diabetes Federation (IDF) and the Japanese Society of Internal Medicine (JSIM). Serum levels of high-density lipoprotein-cholesterol and fasting glucose, as well as blood pressure (BP), were significantly higher in winter than in summer, whereas waist circumference and serum levels of triglyceride exhibited little change. The prevalence rates of NCEP, IDF, and JSIM metabolic syndrome in this study were 3.8, 15.1 and 12.4% in winter and 3.2, 10.7 and 8.4% in summer, respectively. Of all metabolic syndrome components, an elevated BP was most significantly correlated with the seasonal variation of metabolic syndrome prevalence. This study demonstrated seasonal variations in metabolic syndrome prevalence in Japanese male workers. These results indicate that the season of health checkups may affect the clinical diagnosis and management of metabolic syndrome.

Seasonal variation in serum lipid levels in Japanese workers.

AIM: Seasonal variation in serum lipid levels in the Japanese population remains unclear. The aim of this study was to determine whether a variation in lipid levels exists in Japanese workers. METHODS: We investigated 1,331 employees in our institution (1,192 men, 44+/-10 years; 139 women, 38+/-11 years) who underwent health checkups in both June (summer) and December (winter), 2008. RESULTS: Serum levels of low-density lipoprotein (LDL) and high-density lipoprotein (HDL) cholesterol, and triglyceride were significantly higher in winter than in summer (129.1+/-31.2 mg/dL versus 125.2+/-30.2 mg/dL, p<0.0001; 65.9+/-16.8 mg/dL versus 63.5+/-16.1 mg/dL, p<0.0001; 110.4+/-67.5 mg/dL versus 107.5+/-70.4 mg/dL, p<0.05; respectively), although the ratio of LDL to HDL cholesterol was comparable (2.11+/-0.81 in summer versus 2.12+/-0.81 in winter). The frequency of study subjects diagnosed with hypercholesterolemia, defined as LDL cholesterol > or = 140 mg/dL, was significantly higher in winter than in summer (34.5 % versus 30.9 %, p<0.0001). CONCLUSION: In Japanese workers, we demonstrated that there is a seasonal variation in serum lipid levels and the prevalence of hypercholesterolemia. This result indicates that we have to give careful consideration to the season of blood sampling in the clinical diagnosis of and management decisions for hypercholesterolemia.