MEDICAL MATTERS:Brace yourself for a scorcher this summer, writes MUIRIS HOUSTON
WITH THE worst of the cold weather [hopefully] behind us, I thought this week’s column might spread some much-needed warmth if it looked at hot weather and the effects it can have on health. Indeed, it may turn out to be prescient: the postman and amateur meteorologist from Donegal who last autumn correctly predicted the prolonged cold spell would last into March, has said we can expect an absolute scorcher in June, July and August this year.
If his predictions do come to pass it may convince some that, despite the worst winter for 40 years, global warming is a reality. Following problems experienced in Paris in 2003, when about 3,000 people died as a result of two weeks of record-breaking weather, some cities across the world have already introduced public health protection measures.
The health risks of extreme weather events such as periods of very high temperature, torrential rains, flooding and drought have been relatively well studied.
When temperature is plotted against the number of daily deaths, a typical U-shaped relationship emerges: the middle trough represents a comfort zone where we are not stressed by heat or cold. The right side of the curve shows the death rate increasing with temperature, with older people most likely to die during extreme heatwaves. Others vulnerable to heatwaves are children and those with mental illnesses. And those with pre-existing illnesses such as heart attack, stroke and chronic breathing problems are most at risk.
Doctors from Canada and the UK reviewed the health effects of hot weather in last week's Lancet. They explain that while human adaptation to cold environments is greatly assisted by behavioural responses such as wearing additional layers of clothing, adaptation to heat is dependent on the body's ability to act as a natural cooling system. Human beings maintain an internal temperature within a narrow range of about 37 degrees. The main ways in which the body eliminates heat during thermal stress are through sweat production, increased cardiac output and redirection of blood flow to the skin. These responses can be diminished or delayed in elderly people or other susceptible groups such as those with chronic illness or people taking certain drugs such as diuretics.
Is overheating dangerous? Signs of heat-related illness begin with heat exhaustion, which can progress to heatstroke. This is defined as a core body temperature of at least 40.6 degrees. Progression to death in an individual with heatstroke can happen within hours. Even with prompt medical care, some 15 per cent of heatstroke cases are fatal. Rates of heat-related mortality and morbidity are high in older people and in those with chronic diseases of the kidney, lungs and heart.
It is less clear cut if people with diabetes, neurological disorders and psychiatric illnesses may also be at increased risk.
Some results from physiological studies have shown that young children might be unable to meet the need for increased cardiac output in hot conditions. And social deprivation has been identified as a risk factor for heat-related death in many US studies, but the evidence from Europe is not as clear.
From an environmental perspective, living in homes with high thermal mass and little ventilation, and living on the upper floors of high rise buildings pose an added risk.
So, assuming our amateur meteorologist is right and temperatures hit the mid-30s or higher for days at a time this summer, is there anything we can do to minimise the effects? There is an urban rural divide in the risk posed to health by extreme heat so a temporary move out of the city might be in order. But the strongest scientific evidence is for the following preventive measures: increase your fluid intake but older people should drink water often without waiting to feel thirsty; stay in a cool or air-conditioned environment and wear loose-fitting clothes; and reduce your normal activity levels.
Small amounts of alcohol drinks are probably okay, but avoid spirits completely.
Now, where are my sunglasses?