Can sleep-deprivation decrease the cognitive performance?

Hello doctor,

It is known that many teenagers suffer from sleep-deprivation. My son has also suffered from sleep-deprivation. He is now 21 years old. According to his physicist, each day's recommended amount of sleep is minimal eight hours for teenagers aged between 13 to 18. This has not been the case for my son since he was 13 years old. An accurate estimation of his sleep pattern would come close to about seven hours of sleep each day.

Recent research has provided us insights into how sleep-deprivation could lead to permanent cognitive impairments as a result of neuronal death. My son states that he feels like his cognitive performance has decreased in comparison to his early teens. He even claims that his IQ has decreased measurably. He regrets not having slept enough but is realistic in that he is not the only individual who has had or still has this condition. It is not clear if his explanation for the cognitive decrease in performance is warranted as the brain is very complex. Neuronal death occurs every day and is part of a natural process of ageing. Now a more detailed and accurate clarification based on these questions is needed from you.

What is the permanent impact and significance of sleep-deprivation on neuronal death in comparison to the natural process of ageing? Ageing might put the permanent damage of sleep-deprivation in perspective as aging, and thus, neuronal death is unavoidable. Simply put, might sleep-deprivation cause faster ageing of the brain? If so, would the brain of a 20-year-old be similar to a brain of a 30-year-old because of sleep-deprivation? Or is the increased ageing very insignificant? Might the effect of sleep-deprivation have significantly reduced his IQ?

Do adults suffer more or less from neuronal death than teenagers during sleep-deprivation? This puts the impact of sleep deprivation on the brain in perspective as he might sleep better than other adults and recover more steadily in comparison to other adults. Are teenagers more prone to permanent cognitive impairments from sleep-deprivation than adults? Is the damage more easily recoverable during teenage years than in adulthood?