The New York Times announced: “At Least 1 in 4 N.F.L. Players Gets Brain Disease.” An LAist segment said one in four “will get” CTE. UPI also said one in four “gets” it.

The important verbs were gets and will get.

The important missing words were who died from 2016 to 2021.

Here is the BMJ study in arithmetic:

  • Former NFL players who died during 2016–21: 878\
  • Donated brains examined: 235\
  • CTE diagnoses: 215\
  • Deaths without an examined brain: 643\

The 215 confirmed cases amounted to 24.5 percent of all 878 deaths. That was the number that became “one in four.”

Among the 235 examined brains, however, 91.4 percent had CTE.

Neither percentage answers the question posed by those broad headlines.

The 24.5 percent figure is a lower bound. To calculate it, researchers treated all 643 unexamined cases as though they had no CTE. This was not a medical finding about those players. It was one edge of the arithmetic.

At the other edge, if all 643 had CTE, prevalence in the death cohort would have been 97.7 percent.

The true figure lies somewhere within that large and unpleasant space. The study did not determine where. Brain donation was not random, so the 91.4 percent found among donated brains cannot simply be pasted onto everybody else.

The 643 unexamined cases remained unknown.

Unknown is an old word. It continues to mean unknown despite considerable investment in communications.

The careful version is not comforting. Researchers confirmed CTE in 215 former players. The actual number in the death cohort might have been much higher.

But seriousness does not turn a prevalence floor at death into a lifetime forecast for the living.

CTE was ascertained postmortem in this research. Neither the study nor the accompanying BMJ editorial supplied a diagnosis for a living player or estimated the lifetime risk faced by current or younger players. A prospective cohort would be needed to estimate that risk more precisely.

Several news organizations managed to keep this distinction alive. CBS News and CNN put the death cohort and its dates in their headlines. The Boston Globe retained “at time of death” and gave the timeframe immediately.

No special typeface was required.

The Times and UPI supplied important cohort and method details farther down. That is better than not supplying them. It still does not make gets mean was confirmed among former players who had died.

The clean sentence is this:

Among 878 former NFL players who died from 2016 through 2021, researchers confirmed CTE in 215, establishing a 24.5 percent floor for prevalence at death. They could not determine the true prevalence because 643 were not examined.

The sentence has more furniture. Facts often do.

Two hundred fifteen confirmed cases require no salesmanship. The unknown cases require honesty. The living should not be handed somebody else’s autopsy as a personal prophecy.

Say what happened.

Leave the future where it is.