When there's a real chill in the air, your risk of being hospitalised for heart failure rises, a new study suggests.
"In the past, seasonal differences have been noted for heart attacks and strokes," said study co-author Dr Abhishek Deshmukh, a cardiac electrophysiologist with the Mayo Clinic in Rochester, Minnesota.
"We looked at seasonal differences in patients getting hospitalised for heart failure and atrial fibrillation from a large national hospitalisations database," he added. "We found that during cooler months, especially in February, the rates of hospitalisations are the highest.
"It is striking that people get more sick with cardiac diseases during winter months," Deshmukh said. "Whether it is the cooler air, after-effect of holiday season or other environmental triggers needs further studies."
Deshmukh and his colleagues were to present their findings at a meeting of the Heart Rhythm Society, in San Francisco.
More than five million Americans experience heart failure every year and as many as 6 million may have atrial fibrillation, according to the U.S. Centres for Disease Control and Prevention.
The study focused on hospitalisations that occurred between 2002 and 2012 due to heart failure. That information included more than 12 million patients, a third of whom also had atrial fibrillation.
Averaging the frequency of hospitalisations across the 10-year period, the researchers found that both those with heart failure and those with heart failure and atrial fibrillation were "notably" more likely to be hospitalised during winter months compared with summer months.
The lowest month for such hospitalisations was July, the study authors said. But in the months after, hospitalisations climbed, reaching their highest rate in February. From that month forward, however, the figures started to decline, until again reaching a low point the following July.
Though Deshmukh said it's unclear what exactly drives these seasonal differences, he identified a number of "plausible reasons". They include: seasonally provoked changes in bodily fluid balances, changing levels of naturally occurring hormones, a rise in infection risk, and shifting air pollution environments.
The cooler ambient air of winter may itself serve as a potential trigger, he added, given that cooler air can provoke an increase in blood pressure.
More respiratory tract infections
That point was seconded by Dr Gregg Fonarow, a cardiology professor at the University of California, Los Angeles.
"Blood pressure is higher in winter, which can worsen heart failure," he said. "Also during winter months, there are higher rates of respiratory tract infections, which increase heart failure risk."
An increase of salt intake in winter months may also be problematic, he noted.
Deshmukh said he believes that increasing "awareness of this 'winter effect' may lead to more attention to symptoms".
Still, is there anything patients can do to proactively cut down the likelihood of cold weather heart trouble?
Unfortunately, no, said Deshmukh, who added that more research is needed to explore what steps patients can take to modify or diminish the wintertime risk.
Meeting results are typically viewed as preliminary until published in a peer-reviewed journal.