Heat waves and mortality among vulnerable groups

2010-08-26

It is estimated that climate change poses different types of health threats worldwide. The heat wave in Europe in 2003 had consequences for public health due to the large increase in the number of deaths that occurred. Because preventive measures must be directed at relevant groups in order to be successful at a reasonable cost, it is important to find out more about the effects of heat waves on mortality in different vulnerable groups.

In order to increase knowledge about vulnerable groups, an analysis has been carried out by The Occupational and Environmental Medicine Unit, Umeå University, on behalf of The Swedish National Institute of Public Health (SNIPH). The analysis was carried out in cooperation with the research programme Climatools. The study was based on knowledge about vulnerable groups and on results of previous studies conducted in other countries.

To a large extent, the result of this study is similar to results from studies in other countries. For example, among people who have previously been admitted to hospital for a mental illness (for example dementia) the number of deaths increases by up to 90% during the seventh day of the heat wave. This may be due to the fact that people with mental illnesses have difficulty in understanding their bodily signals accurately and therefore do not perceive the risks associated with excessive heat. Among persons who have previously been admitted to hospital for Chronic Obstructive Pulmonary Disease (COPD), mortality increases by over 60% on the seventh day of a heat wave. Diseases which increase vulnerability to heat are more common among elderly people. This study shows no increased impact on mortality among women, which has been stated in previous European studies. This may have to do with a more equal standard of living in Sweden than in other countries.

This study of Swedish data shows that the duration of a heat wave is of great importance to mortality. The results suggest that heat alerts and targeted actions should therefore be also based on how long the heat wave will last. It is probably more effective if warnings are given and actions taken when the weather forecast says that it will be hot for a number of days rather than giving warnings for every single hot day. In some countries there are systems for real-time monitoring of the number of deaths that occur and now Sweden has also put such a system in place.

Many countries already affected by heat waves have introduced heat alert systems. There are often instructions attached to these warning systems on what should be done when an alert is issued. For example, in the health care sector they may be about increasing the preparedness to handle a larger number of cases. In the sector that cares for the elderly, they could be about close observation of those who are vulnerable to heat.

Some European countries have published regulations for health professionals and information for patients and the general public on how to proceed during a heat wave. The concluding chapter in this report brings together the most common advice given on heat by authorities in the UK and USA.