Professional football players who have experienced a certain type of concussion — one that includes losing consciousness — may have an increased risk of changes in the brain and decline in their memory later in life, according to a new study.

In the study, researchers looked at 28 former NFL players, including 17 who had experienced a concussion with loss of consciousness. The researchers conducted brain scans and tested the former players' memories, and compared them with those of 27 men who had not played football or had a concussion. The average age of the retired football players was 58, and the average age in the comparison group was 59.

The researchers found that the former athletes who had lost consciousness during a concussion had smaller hippocampuses — a part of the brain involved in memory function — than the men without football experience.

"The occurrence of loss of consciousness really seems to be an important factor in cognition and brain structure later in life," said study author Munro Cullum, a neuropsychologist at the University of Texas Southwestern Medical Center in Dallas. [10 Ways to Keep Your Mind Sharp]

The smaller hippocampus became apparent in the men starting at age 63, the researchers found.

"After age 63, there seems to be an effect of having a history of concussion with loss of consciousness and a decline in memory, and a decline in brain structures responsible for memory," Cullum told Live Science.

The former football players who were older than 63 and had experienced concussion with a loss of consciousness were also more likely to be diagnosed with mild cognitive impairment than the other players. Mild cognitive impairment is a condition that involves problems with thinking and memory, and can be an early sign of dementia.

In fact, all seven of the retired athletes older than 63 in the study who had lost consciousness during a concussion had been diagnosed with mild cognitive impairment, whereas only one former player who did not suffer a concussion that included a loss of consciousness had mild cognitive impairment, the researchers found.

The good news for the players is that the researchers did not find anyone with severe memory impairment in the group, Cullum said. There was also no relationship between the number of games the former athletes played and their risk of mild cognitive impairment, the researchers said.

In addition to a concussion that includes a loss of consciousness, there are probably other factors involved in a person's risk of developing memory problems, Cullum said. Some of these factors may be genetic, he added.

"Not everyone is going to develop memory problems later in life, but it appears that if you have a history of concussion with loss of consciousness, you are at a greater risk for cognitive and memory problems later in life," Cullum said.

The study was published today (May 18) in the journal JAMA Neurology.

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