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Study finds seasonal change in cholesterol levels

Blood cholesterol levels peak during autumn and winter but decline in spring and summer, perhaps because warm weather and more activity add volume to the blood, researchers announced.

The report from the University of Massachusetts Medical Center in Worcester was based on a study of 517 healthy men and women who were tracked quarterly over a year on their diet, physical activity, exposure to light, general behavior and cholesterol.

It found that the average cholesterol level was 222 milligrams per deciliter of blood in men and 213 in women. If a patient's total blood cholesterol is between 200-239 milligrams per deciliter, that reading is considered borderline high and means lifestyle changes are needed to avoid a heart attack, according to a National Heart, Lung and Blood Institute Web site. A reading above 240 milligrams is considered high or in "the danger zone," the Web site said.

Among men studied, cholesterol levels increased on average by 3.9 milligrams per deciliter of blood, peaking in December, and in women by 5.4 milligrams, peaking in January.

In general the increases were greater in those who had elevated cholesterol levels to begin with. Nearly a quarter of those studied went above the 240 marker in the winter, the study said.

The report, published Monday in the Archives of Internal Medicine, said warmer weather in the summer and more activity probably contribute to a dilution of the blood cholesterol. Among other things exercise facilitates sodium and water retention, the report said.

The authors said it is possible that some people may be misdiagnosed with high cholesterol if measurements are taken in winter -- if the damage to arteries that high cholesterol does is based on an absolute amount, diluted or not.

But it said season-specific cholesterol guidelines are not warranted based on this study. The authors called for more research "to better understand the mechanism through which physical activity and temperature control systems could aid in the prevention of coronary heart disease, morbidity and mortality."

Posted by thinkum at April 27, 2004 03:01 PM