How to cope with heat illness

Every time the weather heats up in Hong Kong, hospital admissions increase correspondingly. Summer temperatures can often be brutal, and global climate change has made the mercury rise even higher in recent years, leading to greater incidences of heat-related illnesses.

A study conducted between 1998 and 2009, and published online in the Bulletin of the World Health Organisation, uncovered a link between weather phenomena and pollution levels, and hospital admissions.

Out of the more than 7.9 million hospital admissions that were recorded during the 11-year study period, 33 per cent of them took place during the hot season. During this season, admissions increased by 4.5 per cent for every increase of one degree Celsius above 29 degrees, with respiratory ailments accounting for most of those hospitalised.

Heat illness refers to disorders that are caused by environmental heat exposure. Besides heat stroke - which is life threatening - heat illnesses include heat rash or "prickly heat", heat cramps, heat syncope and heat exhaustion. Up to a certain degree, physical activity in warm or hot weather is harmless. When the body overheats, natural processes kick in to help bring down its core temperature.

Sweating occurs, which cools the body directly as the moisture evaporates from the skin. Dermal blood vessels dilate, bringing more blood out to the body's periphery and transporting excess heat to the surface of the skin, where it is released. Overall, the body has to work harder to protect it from the dangers associated with overheating.

But when the ambient temperature is too high, the body's cooling processes can become ineffective. Heat dissipation is reduced, and, if humidity is high and there is no breeze, the vapour barrier can prevent the sweat from evaporating from the skin, says Dr Hans Schrader, executive medical director at Matilda International Hospital.