Former players with memory problems and a history of concussion did worse on the memory tests than people without a history of concussion or athletes without memory problems, the researchers found. However, retired football players who had at least one concussion with loss of consciousness had a smaller hippocampus compared with retired players who never had a concussion or people who never suffered a concussion or played football.
Dr. Cullum noted that a concussion with loss of consciousness may increase the risk for memory problems beyond the normal risk associated with an aging brain.
Dr. Robert Glatter, director of sports medicine and traumatic brain injury at Lenox Hill Hospital in New York City, said, "We are now beginning to understand that repetitive hits to the brain over time -- without concussion or loss of consciousness -- can be an important marker for mental impairment and memory loss and potentially other neurodegenerative disease such as dementia or Alzheimer's," he said.
Dr. Robert Duarte, a neurologist and concussion expert at North Shore-LIJ's Cushing Neuroscience Institute in Manhasset, N.Y., agreed that losing consciousness isn't necessary to cause brain damage that can lead to memory problems. "We see that people who have several mild concussions over time also have a decrease in hippocampal volume," he said.
SOURCES: C. Munro Cullum, Ph.D., neuropsychologist, University of Texas Southwestern Medical Center, Dallas; Robert Glatter, M.D., director, sports medicine and traumatic brain injury, Lenox Hill Hospital, New York City; Robert Duarte, M.D., neurologist and concussion expert, North Shore-LIJ's Cushing Neuroscience Institute, Manhasset, N.Y.; May 18, 2015, JAMA Neurology.