Cold weather kills 20 times as many people as hot weather, according to an international study analysing over 74 million deaths across 13 countries.
The findings, published in The Lancet, also reveal that deaths due to moderately hot or cold weather substantially exceed those resulting from extreme heat waves or cold spells.
“It’s often assumed that extreme weather causes the majority of deaths, with most previous research focusing on the effects of extreme heat waves,” said lead author Dr Antonio Gasparrini, from the London School of Hygiene and Tropical Medicine.
“Our findings, from an analysis of the largest dataset of temperature-related deaths ever collected, show that the majority of these deaths actually happen on moderately hot and cold days, with most deaths caused by moderately cold temperatures,” he said.
The UK-funded study analysed 74,225,200 deaths between 1985 and 2012 in 13 countries with a wide range of climates, from cold to subtropical.
Data on daily average temperature, death rates, and other factors – such as humidity and air pollution – were used to calculate the temperature of minimum mortality.
“The majority of these deaths actually happen on moderately hot and cold days”
Around 7.71% of all deaths were caused by “non-optimal” temperatures, said the researchers. Cold was responsible for 7.29% of these deaths, while just 0.42% were attributable to heat.
The study also found that extreme temperatures were responsible for less than 1% of all deaths, while mildly sub-optimal temperatures accounted for around 7% of all deaths.
Dr Gasparrini said: “Current public-health policies focus almost exclusively on minimising the health consequences of heat waves.
“Our findings suggest that these measures need to be refocused and extended to take account of a whole range of effects associated with temperature,” he added.
The countries involved in the study were Australia, Brazil, Canada, China, Italy, Japan, South Korea, Spain, Sweden, Taiwan, Thailand, UK, and the US.