March 28, 2014
Winter’s Cold May Lead To Higher Cholesterol Levels: Study
Brett Smith for redOrbit.com - Your Universe Online
Past research has shown that heart attacks and heart-related deaths rise during the winter months and researchers at Johns Hopkins Ciccarone Center for the Prevention of Heart Disease recently found that increased cholesterol levels may be to blame.
The new study, which is being presented at the American College of Cardiology's 63rd Annual Scientific Session in Washington, DC this week, is based on cholesterol parameters among a sample of 2.8 million adults.
"In this very large sample, we found that people tend to have worse cholesterol numbers on average during the colder months than in the warmer months – not by a very large amount, but the variation is significant," said study researcher Dr. Parag Joshi, a cardiology fellow at Johns Hopkins Hospital. "It confirms findings from smaller studies and raises a lot of interesting questions, including what might be driving these (variations)."
Scientists noted that these conclusions do not mean patients should change their seasonal habits. They said the information does validate a suspected year-long pattern and emphasizes the need to focus on behaviors that are important to reducing cardiovascular risk.
"In the summer, we tend to get outside, we are more active and have healthier behaviors overall," Joshi said. "In the colder months, we tend to crawl into our caves, eat [fat-laden] comfort foods and get less exercise, so what we see is that LDL and non-HDL [bad cholesterol markers] are slightly worse. So you have a lipid signature of higher risk, but it's probably driven by a lot of behaviors that occur with the changing seasons."
The study team theorized that more time spent indoors during the winter may mean less sun exposure and therefore lower concentrations of vitamin D, which has been linked to cholesterol level.
To reach their conclusion, the scientists reviewed lipid profiles in over 2.8 million American adults who were sent for tests by their doctors between 2006 and 2013. Samples were classified by the time of year when cholesterol was assessed and evaluations were made over the course of the seasons. The study also evaluated gender-stratified lipids and the incidence of national guideline-based goal achievement for low density lipoprotein (LDL), non-high density lipoprotein (non-HDL) and high lipoprotein (HDL), according to season.
The team found that overall cholesterol, LDL cholesterol and non-HDL cholesterol levels were all greater in the winter. LDL and non-HDL cholesterol were 3.5 percent higher in males and 1.7 percent greater in females during winter compared to the summer. Non-HDL - overall cholesterol minus good HDL cholesterol is considered a comprehensive marker of risk. Women and men had distinctions in overall cholesterol of around 2 mg/dL and 4 mg/dL, respectively, between the warmer and colder months. HDL did not fluctuate much throughout the year.
The researchers also found that women had more encouraging risk profiles overall, yet a lower ratio of women met guideline-based goals compared to men. They called for more research to determine what might be behind these seasonal fluctuations.