Pаssаge B Trаumatic brain injuries are assоciated with cоgnitive decline later in life, and a sharper drоp in cognition as we age, a study of twins who served in World War II shows.There is robust research demonstrating a relationship between head injuries and cognitive impairment or dementia later in life, “but I do not know of any others that use a twin-study design,” said Holly Elser, an epidemiologist and resident physician in neurology at the University of Pennsylvania who peer-reviewed the study.The study published in Neurology on Wednesday found that individuals who had a traumatic brain injury were more likely to have lower scores on cognitive tests when they were about 70 years old.They were also more likely to have rapidly declining scores after their first test if they had multiple traumatic brain injuries, lost consciousness because of a head injury or were 25 or older when the injury happened.“Even if it’s just a single traumatic brain injury, we now know that it led to worse cognitive outcomes later in life,” said Marianne Chanti-Ketterl, the lead author of the study and an assistant professor in psychiatry and behavioral sciences at the Duke University School of Medicine.The study of identical and fraternal twins allows researchers to compare participants to each other while controlling for some, if not all, of the underlying genetic factors and some of the twins’ early life conditions. Identical twins share 100 percent of their genes, while fraternal twins share about half. Which of the following conclusions about head injuries can most reasonably be drawn from the passage?
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