Climate Warming will not Decrease Winter Mortality

by Allison Hu

It has been commonly assumed by policymakers and health professionals that harmful health impacts of anthropogenic climate change will be partially offset by a decline in excess winter deaths (EWDs) in temperature countries as winters warm. However, over the past few decades, the UK and other temperate countries have also simultaneously experienced better housing, improved health care, higher incomes and greater awareness of the risks of cold. Therefore, it is possible that the link between winter temperatures and EWDs is not as direct.

Staddon et al. (2014) investigated the key causes that underlie year-to-year variations in EWDs. They demonstrated that three distinct periods in EWD changes were apparent. In 1951–1970, EWDs exhibited very high year-to-year variation and a strongly decreasing overall trend. Then in 1971–2000, year-to-year variation EWDs halved compared with the preceding period and the decreasing trend continued, albeit less strongly. Lastly in 2001–2011, year-to-year variation was very small and the EWD rate was flat. Furthermore, by analyzing more recent data and carrying out rolling correlation analysis on time-detrended data, Staddon et al. show unequivocally that the relationship of year-to-year variation in EWDs with the number of cold days in winter of less than 5 ◦C that was evident until the mid 1970s has disappeared, leaving only the incidence of influenza-like illnesses to explain any of the year-to-year variation in EWDs in the past decade. Though EWDs continue to exist, winter cold severity is no longer a good prediction of the numbers affected.

Staddon et al. used a threshold model to identify a strong relationship between the annual number of cold days and EWDs before the mid-1970s and to show that this relationship has since disappeared. The relationship between mortality and local daily temperature is variable and specific to local areas and it is likely that the exposure–response relationship of daily mortality to temperature will have changed over the past decades in response to improved housing, health, and wealth. This data analysis concludes that there is no evidence that EWDs in England and Wales will fall if winters warm with climate change. These findings have important implications for climate change health adaptation policies and for health policies in general.

Potential increases in future winter temperature volatility suggests that EWDs are more likely to rise than fall. Additionally, regardless of whether climate-change-induced winter temperature volatility increases the risk of EWDs, the absolute number of EWDs may increase in the future because of increases in the population. Thus, it is important that the recent policy focus on protecting the population from heatwaves should not be at the expense of preventing the much more numerous EWDs. Energy efficiency regulations and government retrofitting initiatives to improve the thermal efficiency of older homes should continue to benefit both health and climate change mitigation. Staddon et al. also believe that particular attention should also be paid to public health initiatives to reduce the risk of infection with flu-like illnesses, including promoting the influenza vaccination, and urgently reducing greenhouse gas emissions to mitigate against climate and weather change also essential.

 

Staddon, P. L., Montgomery, H. E., Depledge, M. H., 2014. Climate warming will not decrease winter mortality. Nature Climate Change, 4, 190-194.

 

 

 

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