Monthly Archives: March 2014

Seasonal fluctuations in cholesterol levels

March_Part 2_LipidologyCholesterol levels fluctuate based on the time of year with more unfavorable lipid profiles seen in the colder months, a trend that may be driven by related behavior changes, according to research presented at the American College of Cardiology’s 63rd Annual Scientific Session.

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 among a sample of 2.8 million adults – the largest study to look at seasonal lipid trends in U.S. adults to date. Abnormal cholesterol levels are a well-known cardiovascular risk factor.

“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, M.D.,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].”

Researchers caution these findings do not mean patients should have their cholesterol checked more frequently or at certain times of the year; the data instead validates a clear seasonal pattern and underscores the need to pay attention to behaviors that are critical to minimizing 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.”

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 this cross-sectional study, researchers analyzed lipid profiles in more than 2.8 million consecutive U.S. adults who were referred for testing by their doctors from 2006 to 2013. Samples were categorized by the time of year when cholesterol was measured and comparisons were made across the seasons. The study also compared gender-stratified lipids and the prevalence of national guideline-based goal attainment for low density lipoprotein (LDL), non-high density lipoprotein (non-HDL) and high lipoprotein (HDL) by season.

Total cholesterol, LDL cholesterol and 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 percent and 1.7 percent increase, respectively. Non-HDL – total cholesterol minus good HDL cholesterol – is a more comprehensive marker of risk. Triglycerides were 2.5 percent 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. HDL did not vary much between seasons. Ratios of atherosclerotic risk were lowest in the spring and summer.

Attainment of National Cholesterol Education Program Adult Treatment Panel III goal LDL-C and non-HDL-C was more prevalent in the summer compared to the winter, while HDL-C was lowest in the fall. Authors also found that while women had more favorable risk profiles overall, a lower percentage of women met the ATP III targets compared to men. The difference between average cholesterol values in the fall and winter were not statistically significant.

Researchers said the distribution of these lipid profiles is analogous to a representative national sample of the current U.S. adult population. Samples were provided through a commercial lab (Artherotech, Birmingham, Ala.), which was not involved with the study or its analysis.

Interest for this study grew out of a sub-analysis from the PROVE-IT trial, a randomized controlled trial looking at the use of low- and high-dose statins after heart attack to see if there was a reduction in events. In this study, the authors also looked at cholesterol values over the year and by season. While this earlier study had similar findings, they were not statistically significant likely because of the smaller sample size, Joshi explained.

Despite these latest findings, he says more research is needed to further tease out what might be behind these seasonal variations.

http://www.medicalnewstoday.com/releases/274685.php

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Early atherosclerotic plaques in the vessel wall regress completely when cholesterol levels are lowered

March_Part 1_LipidologyEarly but not advanced forms of atherosclerotic plaques in the vessel wall disappear when the levels of ‘bad’ cholesterol are lowered, according to a study in mice from Karolinska Institutet, Sweden. The findings, published in PLoS Genetics, indicate that preventative cholesterol-lowering treatment could prevent more advanced, clinically relevant plaque to develop.

Almost half of all deaths worldwide are caused by strokes andheart attacks. The main underlying cause is atherosclerosis, where fat accumulates in the blood vessel walls in the so-called plaques. Atherosclerosis is a progressive disease where advanced and unstable plaques develop over time. When these plaques burst a blood clot is created, which in turn could cause stroke or heart attack, depending on how and where the blood clot is formed. It is therefore preferable to either prevent advanced plaque development, or to reduce and stabilise the plaques in those where they have already developed.

In the current study, the researchers used mice with elevated levels of ‘bad’ cholesterol (LDL cholesterol) which forms advance plaques, similar to what happens in humans with high LDL. With a genetic switch, researchers could also lower cholesterol levels in the blood at any desirable time point. They discovered that when LDL cholesterol was lowered, early plaques disappeared almost entirely, which to some extent surprised the researchers. However, mature and advanced plaques reduced but were still present. In humans, LDL cholesterol can be lowered by using cholesterol-lowering drugs such as statins.

“If lowering of LDL cholesterol affects atherosclerosis in humans in the same way, our observations mean that clinically advanced plaques could be prevented if cholesterol-lowering treatments are administered early enough in individuals with increased risk of cardiovascular disease. However, the perennial problem is to identify these individuals with certainty,” says Dr Josefin Skogsberg at the Department of Medical Biochemistry and Biophysics, one of the principal researchers involved in the study.

The researchers also identified networks of genes that were activated by the cholesterol lowering procedure and caused the regression of the atherosclerotic plaques. There proved to be much greater differences in these networks between early, mature and advanced plaques than what researchers had believed.

“We believe that the regulators of the networks, “network wiring stations” may be suitable parallel treatment targets in order to improve the impact of the LDL cholesterol lowering on the regression of plaque in individuals with mature and advanced plaques,” says Dr Skogsberg.

http://www.medicalnewstoday.com/releases/273304.php

Picture courtesy of medicalmyths.wordpress.com