Why You Can't Stay Awake Forever

Tonight you'll switch yourself off for hours. Your brain won't: for part of the night it burns about as much energy as it does right now. So if it stays busy all night, why do you need sleep at all - and why can't you just stay awake forever? Followed from lights out to morning, with what the measurements support and the part nobody knows yet. Episode 2 of "One Night Inside You". Next: your dreams. What the studies measured (every figure is from the paper, cited as said in the video): brain oxygen use in deep sleep: about 25% below awake, the level of light anaesthesia (Madsen 1991); sugar use, the first brain scans: 43.8% below (Maquet 1990) - more than half is still spent; in REM, back to awake lapses climb with every hour awake past 15.84 a day, added up over the nights; after two weeks of 6 hours or less, some did as badly as after up to 2 whole nights without sleep - and barely felt it (48 adults, Van Dongen 2003) frigatebirds in flight: about 41 minutes of sleep a day, 7.4% of what they sleep on land (Rattenborg 2016) sleep spindles: about 1.9 a minute in light sleep - 3,846,408 counted in 11,630 people (Purcell 2017); a sleep cycle about 90 minutes, 4-6 a night replay: place cells that fired together while rats ran fired together again in sleep (Wilson & McNaughton 1994), in bursts of about a tenth of a second, ~20x faster than lived (Lee & Wilson 2002) synapses: 6,920 traced in mice by 3D electron microscopy; contacts about 18% smaller after sleep - the weaker, more changeable ones (about 4 in 5) shrank, the biggest were spared (de Vivo 2017) the "brain wash": the space between brain cells up 60% in sleeping mice (Xie 2013); a dye left the brain more slowly asleep, not faster (Miao 2024); vessels pumping fluid in deep sleep (Hauglund 2025); in people, a tracer cleared less after one night awake (24 people, Eide 2021) SOURCES Energy: Madsen et al. 1991, J Appl Physiol 70:2597 (PMID 1885454). Maquet et al. 1990, Brain Research (PMID 2350676). Neurons on and off: Vyazovskiy et al. 2011, Nature 472:443 (PMID 21525926); Vyazovskiy et al. 2009, Neuron 63:865 (PMID 19778514). Sleep pressure: Porkka-Heiskanen et al. 1997, Science 276:1265 (PMID 9157887). Van Dongen et al. 2003, Sleep 26:117 (PMID 12683469). Rechtschaffen et al. 1983, Science (PMID 6857280). Randy Gardner, 264 hours: Ross 1965, Arch Neurol 12:399 (PMID 14264871) - the figure via secondary sources (the report has no abstract). Frigatebirds: Rattenborg et al. 2016, Nat Commun 7:12468 (PMID 27485308). Jellyfish: Nath et al. 2017, Current Biology (PMID 28943083). The night: Patel et al., Physiology, Sleep Stages, StatPearls 2024 (PMID 30252388). Purcell et al. 2017, Nat Commun 8:15930 (PMID 28649997). Riedner et al. 2007, Sleep 30:1643 (PMID 18246974). Replay: Wilson & McNaughton 1994, Science 265:676 (PMID 8036517). Lee & Wilson 2002, Neuron 36:1183 (PMID 12495631). Rasch et al. 2007, Science (PMID 17347444). Marshall et al. 2006, Nature (PMID 17086200). Turning down: Tononi & Cirelli 2014, Neuron (PMID 24411729) - a hypothesis. de Vivo et al. 2017, Science 355:507 (PMID 28154076). Clearance: Xie et al. 2013, Science (PMID 24136970). Miao et al. 2024, Nat Neurosci 27:1046 (PMID 38741022). Hauglund et al. 2025, Cell (PMID 39788123). Eide et al. 2021, Brain 144:863 (PMID 33829232). Fultz et al. 2019, Science (PMID 31672896). Dagum et al. 2026, Nat Commun (PMID 41593094) - an investigational device. Nothing here could be measured on our side, so every figure is cited, and the video says where each comes from. Several results are in rats, mice or cats, and the video says so each time. "Replay and turning-down may be one job" is the researchers' proposal, not a result. Whether sleep clears the brain faster than waking is disputed: the mouse labs disagree, the human studies are few and small. The pictures of curves, bars and scans show the shape of each result, not its data. Music: "Colony" - TrackTribe (YouTube Audio Library). The narration is AI-generated, and so are the animations. The research and the editorial judgement are mine. This video explains how the body works; it is not medical advice. 0:00 Your brain never switches off 0:38 Not switched off - the energy 2:16 Why you can't stay awake 4:37 The night shift - one night, stage by stage 5:33 Replay - the day, twenty times faster 7:04 Turning down - the price of learning 8:11 Does sleep wash your brain? 10:07 So what is sleep for? #sleep #brain #science