Cold weather can raise a person's risk of getting a heart attack, says a study led by an Indian-origin researcher.
Krishnan Bhaskaran and colleagues from London School of Hygiene and Tropical Medicine have found that a drop in the average temperature outside is linked to higher risk of people having heart attacks, the 'British Medical Journal' reported.
In fact, each 1 degrees Celsius reduction in temperature on a single day is associated with around 200 extra heart attacks in United Kigdom. Though the reasons behind the increased risk in cooler temperatures is not yet clear, the researchers think it could be down to changes in blood pressure and even blood thickness in colder weather.
For their study, the researchers analysed data on 84,010 patients admitted to hospital with a heart attack in 2003-2006, compared with daily temperatures in England and Wales at the same time.
The results were adjusted to take into account other risk factors like air pollution and rates of flu at the time. The researchers found that a 1 degrees Celsius drop in average daily temperature was linked to a 2 per cent increase in the risk of heart attack over the next 28 days.
The risk was highest in the following two weeks. The researchers said while the risk appeared small, there were 146,000 heart attacks every year in the UK so even a small increase in risk translated into 200 extra heart attacks for each 1C drop on a single day.
Older people between the ages of 75 and 84 andthose with previous coronary heart disease seemed to be more vulnerable to the effects of temperature reductions, while people taking aspirin longterm were less vulnerable.
"We found no increased risk of heart attacks during higher temperatures, possibly because the temperature in the UK is rarely very high in global terms. Our results suggest that even in the summer, the risk is increased by temperature reductions," the report stated.
"Our study shows a convincing short term increase in risk of myocardial infarction associated with lower ambient temperature, operating in two weeks after exposure. From these studies you see an effect on blood pressure going up, the blood getting thicker and the heart working harder. Also the substances in the blood which help it to clot get a bit more concentrated," Bhaskaran said.
However, the researchers called for further studies to help shed light on the role of adaptive measures such as clothing and home heating, and further clarify which groups are likely to be the most vulnerable.
"It might be that some combination of these factors is part of the reason for the effect we have observed, but more research is needed to home in on what the mechanisms are," Bhaskaran said.
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