Cholesterol levels vary by season, get worse in colder months

Cholesterol levels fluctuate based on the time of year with more un-favourable lipid profiles seen in the colder months, an Indian-origin scientist has found.

The trend may be driven by behavioural changes that occur with the changing seasons, researchers said.

While previous studies have shown that heart attacks and heart-related deaths increase during the winter months, researchers at Johns Hopkins Ciccarone Center for the Prevention of Heart Disease were interested in finding out whether cholesterol parameters might follow a similar pattern.

They studied a sample of 2.8 million adults - the largest study to look at seasonal lipid trends in US adults to date.

"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 Parag Joshi, cardiology fellow, Johns Hopkins Hospital, and lead investigator of the study.

"It confirms findings from smaller studies and raises a lot of interesting questions, including what might be driving these [fluctuations]," Joshi said.

"In the summer, we tend to get outside, we are more active and have healthier behaviours 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 behaviours that occur with the changing seasons," Joshi added.

Researchers speculate the shorter days of winter - and limited time spent outside - also mean less sun exposure and, subsequently, lower concentrations of vitamin D, which has also been associated with the ratio of bad to good cholesterol.

In the study, researchers analysed lipid profiles in US adults who were referred for testing by their doctors from 2006 to 2013.

Samples were categorised by the time of year when cholesterol was measured and comparisons were made across the seasons.

Total cholesterol, low density lipoprotein (LDL) and non-high density lipoprotein (non-HDL) cholesterol levels were all higher in the winter than in the summer.

LDL and non-HDL cholesterol were 4 mg/dL higher in men and 2 mg/dL higher in women during the colder vs warmer months - a 3.5 per cent and 1.7 per cent increase, respectively.

Triglycerides were 2.5 per cent higher in men during the winter compared with the summer. Women and men had variations in total cholesterol of approximately 2 mg/dL and 4 mg/dL, respectively, between the summer to winter, researchers found.

The research is to be presented at a meeting of the American College of Cardiology.

3 Replies

  • It is interesting, though it propagates 'fat-laden' foods cause unhealthy blood lipids, whereas carbohydrates increase triglycerides and VLDL.

    Is it possible to discern how these findings correlate with heart-disease incidence?

  • Increase in HDL is not unhealthy. Total cholesterol to HDL ratio is the true marker for heart health. LDL-P ( which is not measured in the standard lipid profile test and which is different from LDL per se) and triglycerides are bad. Both LDL-P and triglycerides are promoted by carbohydrates . Saturated fats promote HDL which is the good cholesterol

  • Exactly sir. This is what i have been repeatedly saying and repeatedly posting relevant resources. But more than 6 decades of brainwashing which still is continuing through network of websites like WebMD and all that at the end of the day want every one to munch the same old Standard American Diet -- High Carb Low fat -- so that drugs sell.

    Not all LDL is bad. On LCHF even large part of LDL is said to be large and fluffy and large fluffy LDL is harmless. Even TG to HDL is a marker for CHD/CVD and also IR. Mere numbers are meaningless it is the ratios that one needs to look at.

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