According to the article, a variety of studies have suggested that cholesterol levels are higher in the fall and winter than they are in the spring and summer. Although the mechanism for this phenomenon is not clear, such variation could result in larger numbers of people being diagnosed as having high cholesterol in the winter, the article states.

Ira S. Ockene, M.D., of the University of Massachusetts Medical Center, Worcester, and colleagues investigated the seasonal variation in cholesterol among 517 healthy volunteers from a health maintenance organization serving central Massachusetts. Data were collected quarterly over a twelve-month period on diet, physical activity, exposure to light, general behavioral information, and cholesterol levels were also measured.

The researchers found that the average cholesterol level was 222 mg/dL (milligrams per deciliter of blood) in men and 213 mg/dL in women. According to the U.S. National Cholesterol Education Program guidelines, 240 mg/dL is the threshold level for hyperlipidemia (high cholesterol). Cholesterol levels were increased by 3.9 mg/dL in men, with a peak in December, and by 5.4 mg/dL in women, with a peak in January. The researchers found that the increases were greater in participants who had high cholesterol levels to begin with. Overall, 22 percent more participants had total cholesterol levels of 240 mg/dL or greater (high cholesterol) in the winter than in the summer. The researchers write that seasonal changes in plasma volume (a component of blood) explained a substantial proportion of the observed increase in cholesterol levels in the winter. The authors also report that there were no statistically significant seasonal changes in dietary and caloric int
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Contact: Michael Cohen
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JAMA and Archives Journals
26-Apr-2004