Brrr! Just as Minnesota is experiencing its first sub-zero temperatures of the year, along comes more research warning of the health risks associated with cold weather.
According to a new study led by researchers at the University of Oulu in Finland, cold spells — low temperatures that last more than two days — are associated with an increased risk of death.
The risk is greatest, the study found, in people with respiratory and cardiovascular disease and in people aged 65 and older.
There’s been plenty of previous research that has shown deaths increase on cold days. In fact, a major international study published last year reported that cold temperatures are associated with about 20 times more excess deaths than hot temperatures.
This new study, however, is the first to summarize the adverse health effects of prolonged cold spells in different groups of people living in various climates around the world, according to its authors.
The negative effect of cold spells on health must be better understood, say the researchers, so that communities can develop effective “early warning systems” to protect people, particularly those most vulnerable, from the effects of the cold.
Study details
The study, which appears in the January issue of the journal Environmental Health Perspectives, reviewed and analyzed 26 previous studies that had estimated the overall effects of cold temperatures on deaths. These studies had been conducted in 13 countries (four continents), including the United States, between 1968 and 2009.
To qualify as a “cold spell,” the temperatures in the previous studies had to be severe and had to last for at least two consecutive days. Although some of the studies defined severe cold temperatures in absolute numbers (such as below 14 degrees F in one study from the Netherlands), most of the studies defined it in percentiles (such as a study from Spain, which defined severe temperatures as ones that dropped below the 5th percentile for a typical Spanish winter.)
The University of Oulu researchers divided the 26 studies into different groups for different types of analyses. Nine of the studies — ones that asked similar study questions and that had comparable measures of effect — were used in a meta-analysis to get a specific measurement of risk. That analysis found that cold spells were associated with a 10 percent increase in overall deaths.
Deaths by respiratory disease and cardiovascular disease were particularly impacted by the cold, rising by 21 percent and 11 percent, respectively.
The relative risk of dying during a cold spell was also significantly higher — by 6 percent — for people aged 65 or older.
“We assume that individuals with cardiovascular or respiratory disease are more susceptible to the adverse effects of cold spells than are healthy people,” the researchers write. Cold temperatures, they point out, can cause blood vessels and airways to constrict — a potentially dangerous effect in people who already have these diseases.
And older people are, of course, more likely to have one of these diseases.
The drop
Interestingly, the researchers also found evidence that it’s not necessarily the low temperatures that are associated with the increase rate of deaths. The effect appears instead to be more strongly linked to the sudden drop in temperatures.
Indeed, their analysis found no strong evidence that the duration of a cold spell had a compounding effect on death rates.
That’s a welcome finding here in Minnesota, given that our sub-zero temperatures are expected to continue at least through Tuesday.
The full study is available to read on the Environmental Health Perspectives website.
