Dropping temperatures and changes in atmospheric pressure can lead to an increase in the risk of heart failure for elderly people, according to a large-scale study – and more care needs to be taken to counter the effects.
The researchers are advising elderly people with a higher chance of heart failure to avoid fog and low cloud in the winter months, and are also asking doctors to keep an eye on the weather as well as the condition of their patients.
According to the team from Université Laval and Université de Sherbrooke in Quebec, Canada, being more aware of the link between cold weather and heart failure could help save lives and reduce the high costs of treating these cardiovascular problems in hospitals.
"Our study shows that exposure to cold or high-pressure weather could trigger events leading to hospitalisation or death in heart failure patients," says one of the team, Pierre Gosselin, from Universitié Laval.
"We know that doctors rarely take the weather forecast into account when treating or making recommendations to heart failure patients. So with the extreme differences in temperature due to climate change, we wanted to show how the weather is becoming a more relevant factor."
The researchers looked at 112,793 people, aged 65 years and above, diagnosed with heart failure in Quebec between 2001 and 2011 (via the Quebec Integrated Chronic Disease Surveillance System or QICDSS database).
Across an average of 635 days, study participants were monitored while readings for temperature, humidity, atmospheric pressure and air pollutants were also measured. The data revealed a higher risk of hospitalisation or death in the winter (October to April) compared to the summer (May to September).
On average, a death or hospital visit due to heart failure was 0.7 percent more likely for every 1°C (1.8°F) decrease in temperature over the previous week. The risk also increased by 4.5 percent for each increase of 1 kPa in atmospheric pressure.
And it's not the only recent research to link a drop in temperatures with an increased chance of a heart attack: a 16-year study covering more than 280,000 patients in Sweden also found that the colder the weather, the more heart attack incidents occurred.
That finding was consistent across different regions of the country and various subgroups, including the elderly and those with a record of previous heart problems.
Research linking dropping temperatures and an increased risk of heart problems stretches back years, but with a changing climate to consider, scientists are keen to gather as much data as possible, especially on the most vulnerable people in society.
As for why this relationship appears, we know the body reacts naturally to the cold: our heart starts beating faster to keep us warm, for a start, and the body also tightens its arteries in response to cold, decreasing thermal conduction in the skin and raising blood pressure as a result.
What's more, hormone changes in response to the cold make the blood more likely to clot. Any of these biological changes can trigger cardiovascular issues as the temperature goes down, perhaps by making existing conditions worse.
"In the majority of healthy people these [cold weather] mechanisms are well tolerated," says one of the researchers from the Swedish study, Moman Mohammad from Lund University. "But in people with atherosclerotic plaques in their coronary arteries they may trigger a heart attack."
While the experts dig deeper into exactly why colder weather starts an increase in hospitalisations and deaths due to heart failure, it's important that we stay aware of the dangers, and stay warm.
For the team behind the Canadian study, it's another factor to consider as our planet starts to see an increasing number of extreme weather events.
"This is particularly relevant for purposes of surveillance in public health in a context of climate changes," write the researchers in their paper.
The findings have been published in Environment International.