Why some people are at risk of heart attacks in winter decoded

Cholesterol levels seem to fluctuate significantly with the changing seasons, which may leave some people with borderline high cholesterol at greater cardiovascular risk during the winter months, a new study has found.
While prior studies have shown that heart attacks and heart-related deaths increase during the winter months, researchers in Brazil were interested in finding out whether the prevalence of high cholesterol - a well-known cardiovascular risk factor - might follow a similar pattern.
"People should be aware that their cholesterol and triglyceride levels vary significantly year-round, which in some cases, may lead to a misinterpretation of a person's actual cardiovascular risk," said Filipe Moura, the study's lead investigator from the State University of Campinas, Brazil.

"This should especially concern those who are near the upper cholesterol limit as they may be at higher risk than expected. This is not to say these patients should have check-ups all the time, but we do have to keep a close eye on them and know seasonal variation may play a role," Moura said in a statement.
Researchers evaluated the lipid profiles of 227,359 individuals who had health check-ups in primary care centers in the city of Campinas, Brazil, between 2008 and 2010.
In this analysis � the largest study to date to evaluate cholesterol levels by season � data revealed that low density lipoprotein (LDL) or "bad" cholesterol increased an average of 7mg/dL during the winter compared to summer.

Researchers said this moderate, but significant, increase in LDL cholesterol was enough to result in an 8 per cent overall increase in the prevalence of high cholesterol during the winter.

While the rise in LDL was more pronounced in women and middle-aged people, Moura said this is most likely due to the larger sample size in these categories after stratification by sex and age.
Cholesterol levels during the summer months painted a very different picture, with higher levels of high density lipoprotein (HDL), the "good" cholesterol, and triglycerides, which were respectively 9 per cent and 5 per cent more prevalent.

Moura, who presented his study at the American College of Cardiology's 62nd Annual Scientific Session, said these fluctuations may be even more pronounced in the United States, Europe or other regions that experience more extreme climate shifts in winter and summer.