New review challenges the eight-hour sleep rule for adults

A new review published in the journal Brain Medicine questions the assumption that adults need a full eight hours of sleep each night, suggesting the figure varies from person to person. The study found that adults in hunter-gatherer communities with limited exposure to artificial light slept an average of 6.4 hours per night, with measurements from participants in Tanzania, Namibia and Bolivia ranging from 5.7 to 7.1 hours. Researchers said those individuals did not compensate for shorter sleep by napping during the day and tended to wake near dawn without alarms. The study also noted that whether the living conditions and health risks of these communities match those of modern societies remains unclear. Larger studies indicate that the optimal sleep duration for health may range from 6.4 to 7.8 hours, depending on sex and the organ system examined. Both very short and very long sleep have been linked to heart disease, stroke, cognitive decline and obesity. The U.S. National Sleep Foundation recommends 7 to 9 hours for adults aged 26 to 64, while acknowledging that 6 to 10 hours may be appropriate for some. Experts also pointed to artificial light as a factor that delays the biological clock and pushes sleep later into the night, further complicating standard recommendations.