Researchers have found that even stored human blood is not immune to the effects of ageing.

In a study published by Scientific Reports, a University of Illinois team of researchers found that the longer blood is stored, the stiffer it becomes, leading to a decrease in functionality.  

Blood bank centers across the United States follow a 42-day established “shelf life” for the nearly 14 million units that are banked annually. The study aimed to determine what effect older blood could have on a patient based on the changes that occur during that 42-day period.

Researchers used spatial light interference microcopy (SLIM) to take time-lapse images of the cells. The team then measured the stiffness of the membrane surrounding red blood cells, and found that even though they retained their shape and hemoglobin content, the membranes got stiffer, which decreased their ability to carry oxygen into the microcapillaries of the body.

“Our results show some surprising facts: Even though the blood looks good on the surface, its functionality is degrading steadily with time,” lead researcher Gabriel Popescu said in a news release.

“In microcirculation such as that in the brain, cells need to squeeze through very narrow capillaries to carry oxygen,” study author Bastanta Bhaduri said in the news release.

“If they are not deformable enough, the oxygen transport is impeded to that particular organ and major clinical problems may arise. This is the reason why new red blood cells are produced continuously by the bone marrow, such that no cells older than 100 days or so exist in our circulation,” Bhaduri said.

The research team hopes the study’s results will help provide another way to monitor stored blood using SLIM, and help physicians determine when to give red-cell transfusions to patients with anemia.

"Functional data from red blood cells would help physicians determine when to give red-cell transfusions for patients with anemia,” study co-author Krishna Tangella said in the news release. “This study may help better utilization of red-cell transfusions, which will not only decrease healthcare costs but also increase the quality of care.”