In the US almost 14 million units of blood are dispensed each year to 4.8 million patients. While blood transfusions undoubtedly save many lives, over the past five years, several studies have found that patients who received transfusions were also more likely to suffer heart attack, heart failure, stroke and death. In 2004, for instance a study of heart patients found that those given transfusions were more than twice as likely to die in their first 30 days after arriving at the hospital and three times as likely to have a heart attack.
The problem appears to be related to how stale the blood is. In the US, red blood cells can be banked for up to 42 days. Some evidence suggests that the longer the blood is stored, the less ability it has to carry oxygen to vital organs like the brain and heart.