The October 2015 Scientific American has a fascinating article on sleep: Beyond Memory: The Benefits of Sleep.
- Sleep is an unconditional necessity.
- College students given an immunization that had normal sleep had a 97% higher antibody response than subjects kept awake all night the following night (one night only!). In another study, antibody protection increased 56% for each additional hour of sleep! With less than six hours of sleep, vaccinations were ineffective (no clinically significant immune response) (Hepatitis B).
- When sleep deprived, negative memories are formed more strongly than positive ones, and cognitive decline occurs more strongly with positive associations; negative associations are least affected.
- Poor sleep can lead to major depression and may contribute to other psychiatric disorders; the use of CPAP (to address sleep apnea) shows a 26% reduction in depression symptoms in one study.
- Five nights of restricted sleep with a dozen men showed that the appetite-stimulating hormone ghrelin increased by 28%. Amounts of leptin (decreases hunger) decline by 18%. The men reported a 23% increase in hunger. In other words, sleep deprivation can lead to weight gain (an idea supported by 50 other studies).
- Children from 6 to 9 years old getting less than 10 hours of sleep were 1.5X to 2.5X likely to be obese. Studies in adults suggest a 50% increase in obesity with less than 6 hours of sleep (average) and an associate with Type II diabetes is also seen.