Bloomberg — Cold weather increases the risk of having a heart attack, particularly for the elderly and those with a history of heart disease, according to a UK study.

Each drop in temperature of one degree centigrade was linked to about 200 more heart attacks, researchers at the London School of Hygiene and Tropical Medicine wrote in the British Medical Journal. They found that the one-degree reduction in average daily temperature was associated with a cumulative two percent gain in risk of heart attack for the following 28 days. The highest risk came within two weeks of exposure.

Those aged 75 to 84 and those with previous coronary heart disease seemed more vulnerable to the effects of cold than other age groups, while those taking aspirin were less vulnerable, researchers led by Krishnan Bhaskaran wrote in the study. The study found no increase in the risk of heart attacks at higher temperatures, "possibly because temperature in the UK is rarely very high in global terms," they wrote.

The results were adjusted for factors such as air pollution, the prevalence of flu, seasonality and long-term trends. The temperature's effect on the heart is unclear, the researchers said.

Researchers analyzed data on 84,010 hospital admissions for heart attacks recorded in the Myocardial Ischaemia National Audit Project from 2003 to 2006. They also examined daily temperatures from the British Atmospheric Data Centre for 15 areas in England and Wales. Each one-degree drop in temperature nationwide on a single day in the UK, which has an estimated 11,600 heart attacks during each 29-day period, would be associated with about 200 more attacks.

"Clinicians should be aware that exposure to environmental heat and cold is a risk factor for cardiovascular disease and should consider this in risk prevention and management," Paola Michelozzi and Manuela De Sario, epidemiologists at the Lazio Region Department of Epidemiology in Rome, wrote in an accompanying editorial.

The British Heart Foundation and the Garfield Weston Trust, which provides funding to charities, supported the study.