Patients given blood transfusions of blood stored 29 days or longer are twice as likely to get a hospital-acquired infection as those receiving newer blood, according to researchers at Cooper University Hospital in New Jersey. Based on a three-year study, these infections ranged from blood stream infections, pneumonia, urinary tract infections, heart valve infections, sepsis and other infections from blood that had degraded over time. The average age of blood used in U.S. blood transfusions is 17 days, the researchers told Reuters.

FDA regulations allow blood to be stored up to 42 days before it must be trashed.

Stored red blood cells experience changes that promote the release of biochemical substances called cytokines that can lower a patient’s immune function and render them more vulnerable to infection, the researchers said.

‘We’re not talking about hepatitis, HIV or other things that are transmitted in the transfused blood, but an increased susceptibility to infection as a result of the transfusion,’ Dr. David Gerber of Cooper University Hospital, one of the researchers, said in a telephone interview.’

Many hospitals use the oldest blood available first, to ensure that it doesn’t go to waste, reports Infection Control Today Magazine. Gerber said that he does not endorse shortening the 42-day FDA policy, saying it could shorten the already finite blood supply, but that further study on blood transfusions is needed.

This study adds another scary element to the already horrific stat we know about bloodstream infections — they account for 25% of all hospital infection-related deaths of adults and children in intensive care units.