People are more likely to die if they have a heart attack in winter than in summer, research suggests.

According to a study of almost 11,000 people who had heart attacks in the UK between 1988 and 1997, they were 19% less likely to survive if the attack occurred in winter.

The increased likelihood of dying may be due to increased blood pressure and heart strain in lower temperatures, and the fact that cold weather increases the chance of blood clots, say the researchers.

Colder months

The team led by Dr Jill Pell, of the department of public health medicine at Greater Glasgow Health Board, also blamed factors including lower levels of vitamin D, higher cholesterol levels and a greater risk of respiratory diseases during the colder months.

People who have heart attacks in winter are usually older, fall ill at home and are less likely to receive defibrillation treatment shortly after the attack. But even taking these factors into account, the chances of survival were still less between December and February than they were between June and August, they said in the medical journal Heart.

Dr Paul Wilkinson of the London School of Hygiene and Tropical Medicine, who is investigating the reason for greater numbers of heart attacks in winter for the British Heart Foundation, said there were clear links between cold weather and heart attacks.

New observation

Referring to the finding that there is a greater chance of dying if heart attacks are suffered in winter, he said: "That is a new observation. There is lots that is unknown about the seasonal variation.

"If that is the case, that would fit with cold temperatures and winter in general being associated with cardiovascular events."

Dr Pell and her team said simple precautions could cut the number of deaths. "These include adequate indoor heating, wearing protective clothing, especially outdoor protection of the face, and avoiding unaccustomed strenuous exercise," they said.