The science of sleep is quietly rewriting what we thought we knew about human performance. Synthesizing recent findings from three peer-reviewed studies, one pattern dominates: sleep debt compounds non-linearly. Most research subjects did not perceive their own impairment, yet cognitive test scores dropped 20–40% after six nights of six-hour sleep — a figure that matches full sleep deprivation benchmarks. Crucially, individual variation is vast. Roughly 3% of the population carries a genetic mutation enabling genuine short-sleep efficiency; for the remaining 97%, claims of thriving on five hours should be treated with deep skepticism. The studies also converge on a surprising rehabilitation finding: two full nights of recovery sleep — not one — are required to restore baseline reaction times. Yet even after recovery, subtle memory consolidation deficits persisted for up to a week. For healthcare practitioners advising patients, the message is unambiguous: frame adequate sleep not as lifestyle advice, but as a clinical intervention with dose-response characteristics on par with exercise.