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By Amanda GardnerTUESDAY, January 17, 2012 ( — Professional football players already vulnerable to memory loss and cognitive problems stemming from repetitive head injuries may be at even greater risk if they also carry excess weight, as many of them do.

In a small new study of retired NFL players, researchers found that overweight players had less blood flow to key areas of the brain and lower scores on mental-function tests than former players of normal weight.

"There was a very significant relationship: As their weight went up, their reasoning scores and memory and attention scores went down," says the senior study author, Daniel G. Amen, MD, founder and medical director of Amen Clinics, a neuropsychiatry clinic and research center based in Newport Beach, Calif.

The modest cognitive deficits seen in the overweight players could translate into everyday slips in memory, judgment, and impulse control—such as forgetting to buy an item at the store, unwittingly saying something inappropriate, or giving in to unhealthy appetites, Amen says.

"The message for all of us is that we need to take our weight seriously, but it's even more important if you have been at a job [that] puts you at risk for brain damage," he says.

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    Although this warning applies especially to athletes involved in collision and contact sports (such as football, boxing, hockey, or soccer), excess weight may even increase the risk of cognitive problems in people who have suffered one-off head injuries in car accidents or other non-athletic situations, Amen says.

    The study findings, which appear in the journal Translational Psychiatry, aren't entirely surprising. Previous studies have found unusually high rates of mental-function problems in former NFL players (especially those with a history of concussions), while a large body of research has linked being overweight or obese to a higher risk of dementia later in life.

    Amen and his team, in fact, have previously found blood-flow abnormalities in the brains of both retired NFL players and overweight non-athletes.

    In the new study, the researchers compared a group of 38 overweight former players to a group of 38 normal-weight individuals. The players were matched by age and football position, to account for the effects of aging and the different risks associated with the various positions.

    The researchers didn't use body mass index (BMI) to measure obesity and overweight, since BMI, a simple ratio of height to weight, doesn't differentiate between muscle and fat—a crucial shortcoming when it comes to professional athletes who may be unusually muscular. Instead, the researchers used the ratio of waist circumference to height. (Men whose waist was more than 53% of their height were considered overweight.)

    The study participants underwent a type of brain scan known as single-photon emission computed tomography (SPECT) and took a series of computer-based tests designed to gauge real-world cognitive function.

    As the authors expected, a higher waist-to-height ratio was associated with less blood flow in certain areas of the brain involved in attention, memory, reasoning, and judgment. Being overweight was likewise associated with lower cognitive-function scores, especially on the reasoning tests.

    Overall, linebackers and linemen—who tend to make helmet-to-helmet contact on nearly every play— appeared to have lower blood flow and test scores than men who played other positions during their career.

    Over time, the combination of excess weight and repetitive head trauma can lead to an increased risk of stroke and chronic traumatic encephalopathy, also known as "boxer's dementia." The good news, Amen says, is that people can lower their risk by losing weight, getting enough sleep, avoiding stress, eating right, and continuing to exercise.