(Inside Science TV) – The longer a person lives, the more wear and tear the body must take. So, it is natural to expect certain signs of  old age, like gray hairs, a few skin wrinkles and even vision or hearing loss.

Now scientists say even blood can't escape the effects of aging. They found that the longer blood is stored in blood banks the stiffer it becomes.

"What we found is that their stiffness is steadily increasing, the cells are getting stiffer as they are stored longer in the bank," said Gabriel Popescu, a physicist at the University of Illinois at Urbana-Champaign.

Donated blood is stored in blood banks for up to 42 days. Scientists found that even though the cells retain their shape, their cell membranes become stiffer and may not function as well in the body the longer the blood goes unused.

"If the red blood cells become stiffer they are unable to deform and squeeze through very small vessels," Popescu said.

Using a special microscope, researchers took time-lapsed images of red blood cells to see how the cells moved – stiff membranes don't move as much. As the membranes get stiffer, it decreases their ability to carry oxygen into the micro-capillaries – the smallest vessels in the body.

"A normal cell on the other hand will show very, kind of, large vibrations, an indication that they're, very deformable, very functional," Popescu said.

Researchers point out that stored blood is very safe to use and hope their study results will help provide another way to monitor stored blood in the future. For example, their imaging method could be used to monitor stored blood since typical microscopes already in use can be easily adapted with the technology to take time-lapse images of the cells.

"Instead of just transfusing the entire amount of blood that is stored, we could actually maybe pick and choose the fresh cells, which our microscope can tell apart," said Popescu.

Reprinted with the permission from Inside Science, an editorially independent news product of the American Institute of Physics, a nonprofit organization dedicated to advancing, promoting and serving the physical sciences.