A SUDDEN onset of cold weather is likely to trigger heart attacks, particularly in people with high blood pressure, researchers say.
While it is known that cold weather heightens the risk of heart attacks by constricting blood vessels, making it harder for blood to flow, the study is the first to document that variations in the weather increase the chance of heart attacks in those with high blood pressure.
The European Society of Cardiology, at a meeting in Munich, was told yesterday that people with hypertension had a 62 per cent greater risk of a heart attack when the temperature was more than 5C lower than the day before.
Yves Cottin and Marianne Zeller, of the University of Dijon in France, said that susceptible people should be careful about activities in cold weather or when temperatures changed suddenly.
Their two-year study of 700 people also found that the rate of heart attacks in people with high blood pressure was twice as high when the temperature was lower than -4C (24.8F). A cold weather front also heightened the likelihood of an attack.
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As well as increasing blood pressure, colder weather can cause blood to become stickier and make it more likely to clot. Cholesterol levels also tend to be higher during winter and a rise in respiratory infections may lead to inflammation, which contributes to the rupture of plaque-clogged arteries.
Hypertension is estimated to affect 40 per cent of adults in England and Wales and has been called the silent killer as its symptoms are often noticed only by chance, and after it has caused long-term damage or increased the risk of kidney disease, strokes and diabetes as well as heart attacks.
A large global study presented at the cardiology conference has found that about 90 per cent of the risk of heart attack could be predicted. The finding is crucial because it had been thought that only about 50 per cent of the risk could be prevented.
Just two factors — an abnormal ratio of bad to good cholesterol and smoking — were responsible for two thirds of the risk of heart attack. Other factors were high blood pressure, diabetes, abdominal obesity, stress and failure to eat fruit and vegetables or exercise daily.
Drinking small amounts of alcohol regularly was found to reduce risk slightly. The study involved more than 29,000 people in 52 countries and it took 262 scientists more than a decade to complete the work. It will be published in the medical journal The Lancet, whose editor called it the most robust study on heart disease risk factors ever conducted.
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Salim Yusuf, Professor of Medicine at McMaster University in Ontario, and one of the researchers involved, said: “This convincingly shows that 90 per cent of the global risk of heart disease is predictable. This is good news. It means we can do something about it.”
One of the most unexpected findings, he said, was the role that psychological, rather than physical, stress played in causing heart attacks. Triggers included tension at home or at work, financial problems, divorce, losing a child or a feeling of loss of control.
The medical experts were also surprised to conclude that the causes of heart disease were the same in every region and race. The condition has become the world’s No 1 killer, with more than 80 per cent occurring in low and middle-income countries.
“The impact of risk factors is the same in every ethnic group and every region of the world,” Professor Yusuf said.
The difference between men and women seen in the West was also observed all over the world. Men usually get heart attacks at about 57, women at 65. Although that sex difference held true everywhere, the study found that in southern Asia, the Middle East and Africa, people suffered heart attacks about ten years earlier than elsewhere.
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Dr Jean-Pierre Bassand, president of the European Society of Cardiology, called it a fantastic study. “It is clear that not a single continent, not a single civilisation, not a single race, can be spared from cardiovascular disease, which will hit humankind more dangerously than the Black Death in the Middle Ages,” he said. “What we need is political action.”