BACKGROUND AND AIMS: We aimed to test the hypothesis that levels of total and low-density lipoprotein cholesterol are increased after Christmas and that the risk of hypercholesterolemia is increased after the Christmas holidays.

METHODS: We conducted an observational study of 25,764 individuals from the Copenhagen General Population Study, Denmark, aged 20-100 years. Main outcome measures were mean total and LDL cholesterol levels. Hypercholesterolemia was defined as total cholesterol >5 mmol/L (>193 mg/dL) or LDL-cholesterol >3 mmol/L (>116 mg/dL).

RESULTS: Mean levels of total and LDL cholesterol increased in individuals examined in summer through December and January. Compared with individuals examined in May-June, those examined in December-January had 15% higher total cholesterol levels (p < 0.001). The corresponding value for LDL cholesterol was 20% (p < 0.001). Of the individuals attending the study during the first week of January, immediately after the Christmas holidays, 77% had LDL cholesterol above 3 mmol/L (116 mg/dL) and 89% had total cholesterol above 5 mmol/L (193 mg/dL). In individuals attending the Copenhagen General Population Study in the first week of January, the multivariable adjusted odds ratio of hypercholesterolemia was 6.0 (95% confidence interval 4.2-8.5) compared with individuals attending the study during the rest of the year.

CONCLUSIONS: Celebrating Christmas is associated with higher levels of total and LDL cholesterol and a higher risk of hypercholesterolemia in individuals in the general population. Thus, a diagnosis of hypercholesterolemia should not be made around Christmas, and our results stress the need for re-testing such patients later and certainly prior to initiation of cholesterol-lowering treatment.