Chronically restricting sleep by as little as one hour per night has drastic and cumulative effects. It can cause longer and more variable reaction times; lapses in attention; propensity to sleep when unstimulated; and irritable, depressed moods.112
Among young adults, restricting the total time spent in bed to 5 hours per night for only 1 week dropped Multiple Sleep Latency Test (MSLT) sleep latencies from 17 to 7 minutes.113
(The MSLT records an individual’s brain electrical activity, eye movements, and changes in chin muscle tonus to measure how rapidly he or she falls asleep and the types of sleep experienced.
Normally-alert adults take an average of 12 minutes to fall asleep on the MSLT.) The International Classification of Sleep Disorders [ICSD-2] clinically defines any MSLT sleep latency of less than eight minutes as “excessive sleepiness.”
112. Van Dongen HPA, Maislin G, Mullington JM, et al. The cumulative cost of additional wakefulness: dose-response effects on neurobehavioral functions and sleep physiology from chronic sleep restriction and total sleep deprivation. Sleep. 2003;26:117-126.
113. Carskadon MA, Dement WC. Cumulative effects of sleep restriction on daytime sleepiness. Psychophysiol. 1981;18:107-113.