Effects and consequences
Brain
One study suggested, based on neuroimaging, that 35 hours of total sleep deprivation in healthy controls negatively affected the brains ability to put an emotional event into the proper perspective and make a controlled, suitable response to the event.The negative effects of sleep deprivation on alertness and cognitive performance suggest decreases in brain activity and function. These changes primarily occur in two regions: the thalamus, a structure involved in alertness and attention; and the prefrontal cortex, a region sub-serving alertness, attention, and higher-order cognitive processes. This was the finding of an American study in 2000. Seventeen men in their 20s were tested. Sleep deprivation was progressive with measurements of glucose (absolute regional CMRglu), cognitive performance, alertness, mood, and subjective experiences collected after 0, 24, 48, and 72 hours of sleep deprivation. Additional measures of alertness, cognitive performance, and mood were collected at fixed intervals. PET scans were used and attention was paid to the circadian rhythm of cognitive performance. Interestingly, the effects of sleep deprivation appear to be constant across "night owls" and "early birds", or different sleep chronotypes, as revealed by fMRI and graph theory.A noted 2002 University of California animal study indicated that non-rapid eye movement sleep (NREM) is necessary for turning off neurotransmitters and allowing their receptors to "rest" and regain sensitivity which allows monoamines (norepinephrine, serotonin and histamine) to be effective at naturally produced levels. This leads to improved regulation of mood and increased learning ability.
Data from international studies demonstrate that "synchronised" start times for adolescents are far later than the start times in the overwhelming majority of educational institutions. In 1997, University of Minnesota research compared students who started school at 7:15 am with those who started at 8:40 am. They found that students who started at 8:40 got higher grades and more sleep on weekday nights than those who started earlier. One in four U.S. high school students admits to falling asleep in class at least once a week.It is known that during human adolescence, circadian rhythms and therefore sleep patterns typically undergo marked changes. Electroencephalogram (EEG) studies indicate a 50% reduction of deep (stage 4) sleep and a 75% reduction in the peak amplitude of delta waves during NREM sleep in adolescence. School schedules are often incompatible with a corresponding delay in sleep offset, leading to a less than optimal amount of sleep for the majority of adolescents. Caffeine
Consumption of caffeine in large quantities can have negative effects on ones sleep cycle. While there are short-term performance benefits to caffeine consumption, overuse can lead to insomnia symptoms or worsen pre-existing insomnia. Consuming caffeine to stay awake at night may lead to sleeplessness, anxiety, frequent nighttime awakenings, and overall poorer sleep quality. Hospital stay
A study performed nationwide in the Netherlands found that general ward patients staying at the hospital experienced shorter total sleep (83 min. less), more night-time awakenings, and earlier awakenings compared to sleeping at home.