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.