Why do older patients die in a heatwave?

More than 11 000 people were registered as dying in France during the first two weeks of August, 2003.1 This confirmed a significant increase in mortality compared with a similar period in recent years. The majority of excess mortality appears to have occurred in older, frail individuals who were thought to have tolerated poorly the extremes of heat experienced in France at that time.2 Some potential mechanisms underlying this increase in death rate are discussed in this article. A diagnosis of heat stroke requires a core body temperature of >40°C and central nervous system dysfunction to be present. Symptoms of altered consciousness and disseminated intravascular coagulopathy are frequently profound in the setting of hyperthermia. Subsequent multi-organ dysfunction and failure contributes to mortality in heat stroke.3 However, many of the physiological changes in renal function and water and electrolyte homeostasis which occur with increasing age could be pertinent to the excess mortality noted in older patients in extremely hot weather. Older subjects have a lower threshold for the development of renal failure, and diminished renal tubular conservation of sodium and water during periods of dehydration. This occurs for a number of reasons. Firstly, the exponential fall in sodium excretion that occurs in younger subjects who are …