For short-term recovery, the brain changes that occur after a single concussion don’t appear to have clear long-term cognitive effects, and symptoms usually disappear within a few days. Return to contact sport should be gradual: the ‘if in doubt, sit it out’ rule-of-thumb is now adhered to by many sporting codes.
A very small percentage of people who sustain a concussion go on to develop what is known as post-concussion syndrome. Symptoms are usually evident within seven to 10 days after a concussion, and can persist for weeks, months, and sometimes years. Why the syndrome occurs remains unclear.
The long-term effects of concussion
While the short-term symptoms of concussion are reversible, research suggests that even a single knock to the head can have severe consequences later in life. For example, figures from one study that analysed the records of more than 160,000 trauma patients identified that, in patients aged 65 and older, just one concussion was associated with a 22-26% increase in the risk of dementia in the following five to seven years.
Even clearer is research showing that neurological damage accumulates with multiple knocks to the head, even when they are apparently symptomless, or ‘sub-concussive’. Repeated concussion has been linked to increased risk of neurodegenerative conditions such as Alzheimer’s and Parkinson’s disease, as well as chronic traumatic encephalopathy (CTE).
Data from studies of former American footballers is staggering. A survey of more than 2000 retired professional players found that those with a history of multiple concussions were three times more likely to have been diagnosed with clinical depression. Another study of death certificates found that the death rate from neurodegenerative diseases was three times higher for pro-footballers than the general population.