Sleep science challenges the universal eight-hour rule

A recent narrative review published in the journal Brain Medicine challenges the long-standing ‘eight-hour rule’ for sleep, suggesting that the ideal duration varies significantly between individuals.

Researchers studying hunter-gatherer communities in Tanzania, Namibia, and Bolivia—groups with minimal exposure to artificial light—found that individuals slept between 5.7 and 7.1 hours per night. These populations did not require long daytime naps or alarm clocks, often waking naturally near dawn. Analyses of pre-industrial societies suggest an average sleep duration of approximately 6.4 hours.

While these findings suggest the eight-hour standard may be an industrial-era construct, scientists note that modern health outcomes may differ due to stress and environmental factors. The National Sleep Foundation recommends seven to nine hours for adults aged 26–64, acknowledging that needs fluctuate based on age, genetics, and health status. Both excessive and insufficient sleep have been linked to health risks, including cardiovascular disease and obesity.