In the study, to be published this week in the journal Brain and Language, researchers at Arizona State University tracked a steeper decline in vocabulary size and other verbal skills in 10 players who spoke at news conferences over an eight-year period, compared with 18 coaches and executives who had never played professional football and who also spoke in news conferences during the same period.
The players included seven quarterbacks, one nose tackle, one cornerback and one wide receiver. Although the small sample size and limited study period prevented reaching definitive conclusions, the findings underscored the need for larger, long-term studies of changes in spoken and written language that could be harbingers of severe brain damage later in life.
And not just for injuries related to C.T.E. Development of a reliable linguistic tool could also help evaluate head injuries among military personnel and victims of domestic violence, said Dr. Javier Cardenas, who directs the Concussion and Brain Injury Center at the Barrow Neurological Institute in Phoenix.
Someday such a test may help scientists detect and monitor a number of neurological disorders, said Dr. Richard Caselli, a professor of neurology at the Mayo Clinic in Arizona — including individuals who are without symptoms, but are at genetic risk for Alzheimer’s disease.
Scientists, patients and families have been dismayed by the failure of drugs to effectively treat or slow the progression of Alzheimer’s. Many experts suspect that patients in their studies have been too late in the disease’s course for the therapies to work. But to find patients in the subtle early stages, they need a diagnostic test.
For decades, doctors said they believed that C.T.E. was limited to boxers. It was called punch-drunk syndrome. More recently, pathologists have reported similar brain damage among a wider range of athletes, like rugby and professional hockey players. Scientists say they believe the biological processes underlying the ailments start many years before recognizable symptoms appear.
Dr. Visar Berisha, lead author of the new study, and his colleagues at Arizona State, have been working for several years to develop tests to identify individuals at risk of brain damage from various ailments.
In 2015, his team reported subtle changes that have been linked to the onset of dementia in former President Ronald Reagan’s speaking patterns during news conferences. These were apparent years before doctors gave him the diagnosis of Alzheimer’s disease in 1994.
The study did not prove that Mr. Reagan suffered dementia that adversely affected his judgment and ability to make decisions while in office. And the new findings about football players do not prove that the players will develop chronic traumatic encephalopathy, said Julie Liss, a communications professor at Arizona State and a co-author of both studies.
Still, findings from other studies provide no reason to expect a decline in linguistic ability in healthy individuals, Dr. Berisha said.
He and his colleagues tracked the words the players and coaches and executives spoke spontaneously in 10,000 pregame and postgame interviews and news conferences from 2007 to 2015, using transcripts of interviews that 11 N.F.L. teams posted on their websites.
Only 28 players, coaches and executives met an important criterion: that each subject had spoken at least 30,000 words in the interviews.
Conversation requires a series of mental steps, starting when the brain identifies the words needed to express an idea. The brain arranges the words in a recognizable order before the individual moves muscles to articulate speech.
The researchers used two standard, simple measures of verbal ability. One was the ratio of the number of verbs, nouns, adjectives and adverbs to the total number of words spoken. The second was a ratio of the number of distinct words a player or coach or executive used in a news conference or interview to the total number of words spoken.
As neurologically healthy individuals age, measures of the complexity of their use of words and vocabulary remain stable or even increase until about the mid-70s. But the study found a distinct difference in language changes between groups of players, coaches and executives over time.
Of the 10 players, seven showed a decline in one of the measures; four showed a decline in both. Of the 18 coaches and executives, eight showed a decline in one measure and five a decline in both. The players were significantly more likely to show signs of verbal deterioration, the researchers concluded.
Many factors like the setting, topic or whether a player was on a winning or losing team can affect language used in a single interview or news conference or over a short period. But “persistent, unremitting change spanning years, as seen in the professional football players studied, can be cause for concern,” Dr. Berisha said.
The researchers did not name the players, but reported their position, age at the time of the first interview in the study, the number of years of college education and how long they had played professionally.
For quarterbacks, Dr. Berisha listed the average number of sacks per game as a proxy for head injuries. Those with fewer sacks showed a less pronounced decline, but the number of players was too small to provide a statistically meaningful finding.
Dr. Berisha’s team is planning a larger study at Arizona State University of football, hockey and soccer players. The athletes will download an app on their smartphones and provide speech samples in the preseason and periodically thereafter. The researchers also will track any concussions the players experience during the season.
The two data sources will form a basis for evaluating speech and language changes over time after a concussion. Dr. Berisha said his team also was “working with industry and several clinics nationally to evaluate its measures on a large scale.”