Brazilian researchers are finding that cholesterol levels increase with winter's arrival and drop again as warmer weather returns.
Whether these changes in cholesterol are putting patients at risk for heart attacks or stroke isn't clear.
Experts say it's a complex picture and these changes might play a role, but there are many other factors to consider.
There are several possible reasons cholesterol varies by season, including changes in diet, exercise and exposure to the sun.
This research is being discussed at the American College of Cardiology's annual scientific session.