Climate and health: mortality attributable to heat and cold

320 www.thelancet.com Vol 386 July 25, 2015 The European heatwave of 2003 showed the potentially disastrous eff ects of heatwaves. About 70 000 premature deaths resulted, notably in France, and a series of lethal heatwaves have subsequently occurred in several countries. However, less well appreciated is the similar burden of mortality from moderately hot weather, which, depending on defi nitions, could be greater than that of mortality attributable to extreme heat in some places. Evidence is accumulating about the health risks of abnormal ambient temperatures. Conventionally, studies either focus on the eff ects of extreme temperature events, or aim to defi ne exposure–response associations between temperature and mortality. However, whether data that are collected at country, or even city, level are relevant to other climatic settings is doubtful. Moreover, a focus on extreme weather (such as heatwaves) might ignore the incremental risk of moderately unusual temperatures. Both high and low temperatures have been reported to be associated with mortality and morbidity from causes such as cardiovascular disease and respiratory disease. Although deaths attributable to cold are substantially more common in most places than are those attributable to heat, they attract far less public attention. In The Lancet, Antonio Gasparrini and colleagues use a very large multicountry database and novel methods to present a quantitative analysis of the attributable risk of ambient temperature for mortality. They collected data for daily mortality, temperature, and other confounding variables from 13 countries, which included more than 74 million deaths recorded in 384 locations across temperate and tropical climates (roughly a third of locations were in the USA). The investigators analysed the data with a time series quasi-Poisson model to obtain the cumulative exposure–response association of temperature and mortality for each location. The total eff ect of a given day’s temperature on the death rate was defi ned as the sum of the eff ect on that day and 21 subsequent days. These associations Climate and health: mortality attributable to heat and cold predicted). With evidence of clinical effi cacy now shown, use of augmentation treatment earlier than at present, before onset of decline in lung function, should be explored. Diagnosis of α1 antitrypsin defi ciency is a single blood test, and the data would suggest that treatment could begin earlier and lung parenchymal destruction could be prevented. Finally, the challenge remains of a means to augment α1 antitrypsin concentrations in patients with α1 antitrypsin defi ciency without the need for intravenous infusions every week, and to do so in a less costly manner (present treatment costs US$ 100 000 per individual per year). We and others are therefore exploring gene therapy strategies to augment α1 antitrypsin concentrations using adeno-associated viral gene transfer vectors, a treatment that can potentially replace α1 antitrypsin augmentation with a single administration.