Sleep Smarter: The Real Range Beyond the Eight-Hour Rule

Eight hours of sleep isn’t a universal rule, new review and studies suggest. Ancestral sleep patterns show flexibility, with hunter-gatherer communities averaging about 5.7–7.1 hours and pre-industrial societies around 6.4 hours, while modern sleep is often delayed by artificial light. Individual sleep needs vary by health and biological sex, with some research hinting at an optimal range of roughly 6.4–7.8 hours depending on the organ and sex. Consequently, guidelines such as the National Sleep Foundation’s seven-to-nine hours for adults aged 26–64 reflect a personal “sweet spot,” not a fixed eight-hour target.