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You are less likely to survive a heart attack in winter than in summer

November 25, 1999

Almost 11,000 people who had suffered a heart attack between 1988 and 1997 were compared. Those whose attacks occurred in the winter tended to have a higher risk profile, in that they were older, more likely to be at home when the attack
occurred, and less likely to be defibrillatedgiven an electrical current to stop abnormal heart rhythms. However, even when these factors were taken into consideration, they were still 19 per cent less likely to survive the heart
attack than their summer counterparts, despite there being no difference in the number of resuscitation attempts made during both seasons. Deaths before admission to hospital were also significantly higher in winter.

The reasons for the variation may be down to colder temperatures increasing blood pressure and heart strain, say the authors: in Britain winter blood pressures exceed those during the summer by around 5 mm Hg. And the evidence
shows that death from coronary heart disease tends to be lower in countries where there are adequate fuel supplies and strict regulations on ambient temperature. Low temperatures tend to increase blood stickiness and therefore the ease with which blood clots.

Other factors include lower vitamin D levels and higher cholesterol levels during the winter, both of which are linked to the amount of sunshine, and the higher levels of respiratory infection during winter, which may also increase blood clotting ability.

As emigration to warmer climes is not an option for most people, say the authors, adequate indoor heating, protective clothing, especially of the face, and the avoidance of sudden strenuous exercise, are all sensible precautions to take, to minimise the risks of dying from a heart attack.


AlphaGalileo Foundation