Why a cold snap is 20 times more lethal than a heatwave

Cold weather kills TWENTY times as many people as hot weather, according to an international study. 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.

Researchers analysed more than 74 million deaths in 384 locations across 13 countries, including the UK.

Lead author Doctor Antonio Gasparrini, from the London School of Hygiene and Tropical Medicine, said: 'It's often assumed that extreme weather causes the majority of deaths, with most previous research focusing on the effects of extreme heat waves. 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.'

The study analysed 74,225,200 deaths between 1985 and 2012 in 13 countries with a wide range of climates, from cold to subtropical.

The countries involved were Australia, Brazil, Canada, China, Italy, Japan, South Korea, Spain, Sweden, Taiwan, Thailand, UK, and USA.

Data on daily average temperature, death rates, and confounding variables - such as humidity and air pollution - were used to calculate the temperature of minimum mortality - the optimal temperature, and to quantify total deaths due to non-optimal ambient temperature in each location. The researchers then estimated the relative contributions of heat and cold, from moderate to extreme temperatures.

Around 7.71 per cent of all deaths were caused by non-optimal temperatures, with substantial differences between countries, ranging from around three per cent in Thailand, Brazil, and Sweden to about 11 per cent in China, Italy, and Japan. Cold was responsible for the majority of these deaths (7.29 per cent), while just 0.42 per cent of deaths were attributable to heat.

The study also found that extreme temperatures were responsible for less than one per cent of all deaths, while mildly sub-optimal temperatures accounted for around seven per cent of all deaths _with most (6.66 per cent) related to moderate cold.

Dr Gasparrini added: '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.'

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