Sleep deprivation — the effects and what counts as sleep deprived

Sleep deprivation refers to getting less sleep than the body needs. For adults, the NHS recommends 7–9 hours per night. Consistently sleeping under 6 hours constitutes sleep deprivation.

Effects of sleep deprivation

• Cognitive: impaired concentration, memory consolidation, decision-making and reaction time (comparable to alcohol intoxication at 24 hours awake)
• Emotional: increased anxiety, irritability and emotional reactivity
• Physical: increased cortisol, impaired immune function, elevated blood pressure, increased hunger hormones (ghrelin) and reduced satiety hormones (leptin)

The self-assessment problem

Research by David Dinges and others shows that sleep-deprived individuals consistently overestimate their own functional capacity — as sleep debt accumulates, people feel less impaired than they actually are. This is why 'I function fine on 5 hours' is almost always incorrect.

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