Decreased mortality as a result of milder winters

In cold and temperate locations, the daily number of deaths increases as the daily wintertime temperature decreases (71,72). However, this rate of increase appears to be considerably less steep than the relationship between mortality and increasing temperature in the summer. Thus, countries in northern Europe have a clear seasonal variation in mortality, with death rates during the winter 10-25% higher than those in the summer (73). A study in Germany suggests that the increased use of central heating contributed to a steady decline in winter mortality from 1946 to 1995 (74).

In Europe, excess winter mortality is especially high in the United Kingdom (75,76). Indeed, relative excess winter mortality in the United Kingdom is approximately twice that in Scandinavian countries (72) and the Russian Federation (77). Social and behavioural adaptation to cold weather plays an important role in preventing winter deaths in high-latitude countries (78). The social or behavioural causes of the large excess mortality in winter in the United Kingdom are not well understood. Seasonal patterns of respiratory infections such as influenza are a significant cause of winter deaths, especially in epidemic years.

A direct increase in mean summer and winter temperatures associated with global climate change would mean fewer cold spells. Many countries with a high proportion of deaths in winter, such as the United Kingdom, are likely to experience a reduction in total winter mortality from milder winters under climate change. Langford & Bentham (79) estimated that 9000 wintertime deaths per year could be avoided by the year 2025 in England and Wales if the average winter temperature increased by 2.5 °C. A meta-analy-sis by Martens (80,81) estimated that an increase in global temperature of 1 °C could reduce winter cardiovascular mortality in Europe.

The recent Eurowinter Study (82) indicates that southern European populations are more vulnerable than their northern counterparts to short-term cold spells. Northern European countries may therefore be more vulnerable to an increase in heatwaves.

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