Health: BAD BLOOD

For patients with acute heart problems, a blood transfusion–an increasingly common procedure–can double the risk of death and triple the risk of another heart attack within a month, according to a study in the Journal of the American Medical Association. Doctors at Duke Clinical Research Institute analyzed data from three big trials involving more than 24,000 patients, 10% of whom had had transfusions during their first 30 days in the hospital. Researchers speculate that transfused blood may lack nitric oxide–essential for delivering oxygen to tissues–and cause harmful inflammation. Transfusions can’t be halted, says the study’s lead author, but cardiologists can be more selective about who gets them.–By Sora Song