But the cases of CTE have shown this progressive, dementia-like array in players well in advance of a typical dementia diagnosis, which typically occurs when people are in their 70s or 80s.

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In a study published last year in the journal Cortex, Dr. Rankin and her colleagues studied the ability to detect sarcasm in 102 patients who had been diagnosed with four progressive diseases that lead to memory loss: frontotemporal dementia, Alzheimer's disease, progressive supranuclear palsy and vascular-cognitive impairment.

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However, the Boston study showed this progressive, tau protein array in football players much too young for a dementia diagnosis, which typically occurs in people in their 70s or 80s.

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