There is no “magic number” that is prescribed for “critical decision-making,” due to the many confounding factors—including variations in tasks and individual needs—and research on the impact of sleep restriction (rather than total sleep deprivation) on cognitive performance is limited. But one point is clear: cognitive performance suffers when sleep is reduced even by modest amounts (one or two hours). Sleep restriction (that is, four to six hours of sleep) has cumulative effects on cognition, especially executive functioning, after just one sleep-restricted episode; and reducing sleep modestly (less than seven hours) on a regular basis can degrade cognitive performance comparable to one to three days of total sleep deprivation (no sleep at all). Other studies have reported a decline in cognitive performance that becomes stabilized, albeit still degraded, between days two through six on a restricted sleep schedule of four to six hours. You must remember that a “sleep debt” will occur from a single episode of sleep deprivation, resulting in subsequent degraded performance, including changes in mood, decreased psychomotor vigilance, and an inability to accurately judge one’s own level of impairment (similar to alcohol intoxication).