Abstract
Background: Previous studies have shown seasonal variation in LDL cholesterol (LDL-C) levels. However, there have been no studies on seasonal variation in LDL-C levels in Ningen Dock examinees.
Subjects: The subjects swere 8,295 men and 6,802 women among Ningen Dock examinees in 2012 who were not going to hospitals for treatment of diabetes, dyslipidemia, hypertension, liver diseases, or malignant tumors.
Results: We first analyzed the data for men. The age-adjusted odds ratios of the subjects with an LDL-C level of >/= 140 mg/dL in each month against July were calculated. The months having the highest and lowest odds ratios were January (odds ratio: 1.89) and July (1.0), respectively. To examine the seasonal variation in LDL-C levels in detail, we compared the average level of serum lipids in summer (June to August) and winter (January to March) after adjusting for confounding factors. LDL-C, HDL cholesterol, and triglyceride levels in summer and winter were 122 mg/dL and 131 mg/dL (p<0.001), 57.1 mg/dL and 58.0 mg/dL (p<0.05), and 131 mg/dL and 129 mg/dL (p=0.441), respectively. When the subjects were divided according to their age, body mass index, or triglyceride levels, LDL-C levels in winter were higher than those in summer in all of the 3 subgroups. Such seasonal variation in LDL-C levels was also observed in women except for those aged >/= 60 year-old.
Conclusion: Ningen Dock data showed seasonal variation in LDL-C levels. Ningen Dock results should be interpreted in consideration of this seasonal variation.
