The study compared pairs of twins where one twin had experienced a traumatic head injury to see how this could affect cognition later in life.
The man awoke with a headache after being attacked by robbers at a bus stop, but thought they'd knocked him out until doctors found the bullet in his head.
The rod pierced his temporal lobe, which handles memory, language, emotions and visual processing, but the man has made a full recovery.
The mother of Kane Davidson has warned other parents of the dangers of unsecured window shade cords after her son's tragic accident.
"This is an important moment for our client and represents a measure of justice for her," one of the girl's lawyers said in a statement.
Joint Staff Surgeon Air Force Brigadier General Paul Friedrichs said it was "extraordinary" that no American soldiers were seriously injured in the January attack.
"A traumatic brain injury is life threatening, not just at the time, but for the rest of your life," the Democratic presidential candidate noted.
Boxer Patrick Day died Tuesday, four days after being knocked out in a boxing match in Chicago. He is one of at least four fighters to die from injuries suffered in the ring in 2019 alone.
Such damage has been seen only in people over 46. He was 27.
But the changes recover after rest.
Half of people who have suffered severe head injuries have trouble maintaining normal sleeping habits and often don't realize it's a problem.
Post-mortem analyses showed 96 percent had chronic traumatic encephalopathy.