A dose of sunshine can help save the lives of heart attack victims, say researchers.

They found that patients recovering in the sunniest part of an intensive care unit were the most likely to survive.

It is already known that lack of sunshine can cause depression and that sufferers can be cured by exposure to more light.

The researchers, In Canada, decided to check whether the story would be similar for other patients, such as heart victims.

They examined the records of 628 men and women admitted to a cardiac intensive care unit over four years after a first heart attack.

Just over half the patients had been in rooms on the north side of the unit while the remainder recovered in rooms on the south side, where sunshine levels were up to ten times higher, says a report in the Journal of the Royal Society of Medicine.

The researchers found that 39 of those on the darker side failed to survive, compared with 21 in the sunny rooms.

‘Deaths were consistently more frequent on the dark side in each of the four years studied,’ said Professor Peter Hays, of the University of Alberta, who led the study.

The findings were most striking among women. Those treated in the sunnier rooms were able to leave the unit one day earlier on average than those on the darker side.

‘Women did less well in the sunless rooms but did just as well as men when treated in the sunny rooms,’ said Professor Hays, adding that previous research had shown lack of sunshine affected women's mental health more badly than men’s.

Sunlight is thought to cause depression by altering the way the brain responds to a ‘mood’ chemical called serotonin. It is not known why the sun affects heart attack victims.

Professor Douglas Chamberlain, a leading cardiologist at the Royal Sussex County Hospital in Brighton, commented yesterday: ‘I’m convinced sunshine is good for the morale whatever medical condition you have.

‘But it would be difficult in practical terms to increase light levels in cardiac units, especially as the sun has been in short supply this summer.