Bryan Johnson· Author
Research suggests that with just four hours of sleep, your cognitive error rates can increase by 30-50%.
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The headline is broadly defensible, but the qualifications matter. Effect sizes vary by population, the strongest claims rest on shorter trials, and credible voices push back on how it's typically framed.
Research suggests that with just four hours of sleep, your cognitive error rates can increase by 30-50%.
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A single night of 4–5 hrs sleep reduces cognition by 20–40%, drops glucose stability by 30–40%, increases accident risk by 400%, elevates inflammatory markers 50–100%, impairs memory consolidation by 40–60%.
I prioritize sleep because getting just 4 to 5 hours can reduce your cognition by up to 40%, which actually makes me worse at my job.