WHY THE RISK OF HEART DISEASE IS HIGHEST IN WINTER
Winter can be a killer. Literally. Compared to the summer months, people are 26 to 36 percent more likely to die in winter from a heart attack, stroke, heart failure, or some other circulatory disease, say Drs. Bryan Schwartz and Robert Kloner of the Heart Institute at GoodSamaritanHospital in Los Angeles. The researchers examined some 1.7 million death certificates from 2005 to 2008 collected at seven U.S. locations that ranged from hot to cold: Texas, Arizona’s Maricopa County, Georgia, California’s Los Angeles County, Washington, Pennsylvania and Massachusetts. Geography had nothing to do with it. No matter where the data were from, the pattern was the same: Many more deaths in the winter than in the summer.
“We thought the winter peak would be more prominent in cold climates like Massachusetts,” said Schwartz, “but the death rates were similar. That means that temperature is a small factor — or not a factor at all.”
One possible explanation is the higher incidence of influenza and depression. Flu season peaks in the winter, and, as Schwartz points out, during winter’s shorter days, people tend to feel more down and discouraged. They may exercise less and not be as careful about what they eat.
For example, “a patient who already has congestive heart failure might not be as adherent to a low-salt diet. That can be enough to promote fluid retention and worsening heart failure and eventually death.”
OR IT COULD BE…
In a separate study, as reported at a European Society of Cardiology conference in 2013, Swiss researchers looked at cross-sectional data from 10 population-based studies over seven countries, encompassing over 100,000 participants.
Findings of the analysis revealed that many heart disease risk factors, such as blood pressure, total cholesterol and waist circumference, were higher in January and February but lower in July and August, compared with the annual average.
Waist circumference was around 1 cm smaller in summer compared with winter, while total cholesterol was on average 0.24 mmol/L lower in summer than in winter. The results also showed that systolic blood pressure levels were 3.5 mmHg lower in summer compared with the winter months.
Study author Dr. Pedro Marques- Vidal of the Institute of Social and Preventive Medicine at the University of Lausanne, Switzerland, noted, “Although this difference is almost irrelevant for an individual, it is considerable for a whole population because the whole blood pressure distribution is shifted to higher values, increasing cardiovascular risk.”
Dr. Marques-Vidal’s recommendation? People need to make an extra effort to exercise and eat healthily during the winter months to protect their health.
FAT CHANCE
The debate over why there are more deaths in winter doesn’t end there.
A new study suggests one reason may be that the cold weather causes brown fat to accelerate the build-up of plaque in blood vessels. Researchers from Sweden and China made this breakthrough discovery while studying mice, as reported last July in the online issue of Cell Metabolism. Like humans, mice have two types of body fat: white fat and brown fat. White fat stores calories, such as in the flab that accumulates around waists and hips, while brown fat burns calories to generate heat.
Cold temperatures trigger brown fat to generate heat. This was thought to be “healthy” for the body because it also helps reduce white flabby fat. But what author Yihao Cao, of the Karolinska Institutet and LinköpingUniversity in Sweden and colleagues found was that exposure to cold accelerated the formation of fatty deposits or atherosclerotic plaques in the mice, which can lead to heart attack and brain hemorrhaging.
It seems that the lower temperatures activated the breakdown of fatty acids in the mice’s brown fat, causing levels of small low-density lipoprotein (LDL) remnants in the blood to rise, thus encouraging more of it to deposit as plaque. And not only did the lower temperature accelerate plaque build- up, but also it made the plaque less stable. Unstable plaque is more likely to rupture and leak stored fat into the blood, causing blockages in vessels in the heart and brain.
At first, the researchers thought the mice would get thinner and healthier when the cold temperatures activated the brown fat. “Instead, we found that they ended up having more fat stored in the blood vessels,” says Cao. “This came as a surprise and was the opposite of what we thought would happen. “If the same is true of humans, then perhaps we should be advising people with cardiovascular diseases to avoid getting cold and to don warm clothes when they step outside in the winter months,” he adds.
THE JANUARY EFFECT
Death and length of stay in hospital are highest in heart failure patients admitted in the month of January, (as well as on a Friday and overnight) according to research presented at the Heart Failure Congress 2013 in Lisbon this past May. The analysis looked at nearly one million hospitalizations for congestive heart failure over a 14-year period in the state of New York from 1994 to 2007.
One theory the scientists were able to disprove is that the holiday spike was caused by alcohol and drug use. The findings did, however, suggest that staffing may have an impact on seasonal variations in mortality and length of stay. “The fact that patients admitted right before the weekend and in the middle of the night do worse and are in hospital longer suggests that staffing levels may contribute to the findings,” says the study’s author, as well the cold weather, he adds.
It may also have something to do with the shock of opening post- Christmas credit card bills.
Source: Heart Failure Today
