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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.