ALTRUISTS who give blood to help others may be prolonging their own lives, say Finnish scientists. They have found striking evidence that men who donate blood are far less likely to have a heart attack than those who are not blood donors.
Jukka Salonen and his colleagues at the University of Kuopio say the results support earlier findings that people with more iron in their bodies are at greater risk of heart attacks. But they hadn鈥檛 counted on the link being so strong. 鈥淲e were extremely surprised ourselves to find such a strong relationship between blood donation and protection against heart disease,鈥� says Salonen.
The team looked at the medical records of 2862 men over a nine-year period. Of the 153 who were blood donors, only one suffered a heart attack, or just 0.7 per cent. In the other group, the figure was more than 12 per cent (American Journal of Epidemiology, vol 148, p 145).
Advertisement
The lower rate of heart attacks among the blood donors may be because blood loss lowers iron levels. In May this year, Salonen鈥檚 team reported in the journal Circulation (vol 97, p 1461) that men with large iron stores in the body were more than twice as likely to have a heart attack as those with low iron stores. Test-tube and animal studies have already shown that high iron levels encourage the formation of a free-radical form of cholesterol that can damage arteries.
Kay-Tee Khaw, an expert in epidemiology at the University of Cambridge, is cautious about the latest results. 鈥淲hat they found is intriguing and I wouldn鈥檛 dismiss it entirely. But we have to be careful. We鈥檝e had our fingers burnt so many times before.鈥�
Khaw points out that more than a quarter of the non-donors were known to have suffered previous heart disease, but for the group of donors the figure was far smaller, just 8.5 per cent. 鈥淚鈥檇 have liked them to take out all the people with baseline heart disease,鈥� she says.
And Salonen concedes that the men who had given blood might well have come from a section of society that is a lot more health-consciousness than average. 鈥淲e tried to allow for this in the statistical analysis, but it鈥檚 possible that some bias remains,鈥� he says.
However, Salonen believes selection bias couldn鈥檛 completely account for the spectacular difference in heart attack rates between the two groups. 鈥淲e鈥檙e convinced a link between blood donation and lowered risk of heat disease exists,鈥� he says. Philip Poole-Wilson of the National Heart and Lung Institute in London is not yet convinced: 鈥淭hey could be right, but it鈥檚 not proven.鈥�
Khaw argues that the only way to find out for sure if donating blood protects the heart is by organising a big study in which healthy people are divided at random into a group that donates blood and a control group that does not. Salonen is already planning this kind of study, though he has yet to secure funding.