Commentary: How much sleep do you need? Forget the eight‑hour rule

Decades ago, the recommended amount of sleep for adults was universally eight hours. This guideline stemmed from an era when work, recreation, and sleep were each allocated eight hours. However, recent research suggests that eight hours may not be the optimal amount for everyone. A new review in Brain Medicine points to evidence that there is no one-size-fits-all sleep duration.

By studying hunter-gatherer communities, researchers have discovered that people naturally sleep between 5.7 and 7.1 hours each night in places like Tanzania, Namibia, and Bolivia. These individuals have minimal exposure to artificial light, which typically disrupts sleep patterns.

Their short sleep durations seem adequate, with no need to compensate with extra daytime naps. People in these societies tend to wake close to dawn, regardless of the day. The average sleep duration among pre-industrialized societies varies based on factors like measurement methods, geographical location, season, and environmental conditions. One recent analysis estimated this average to be about 6.4 hours.

The question arises: is eight hours too much sleep? These studies propose that the amount people naturally sleep may be what they truly need. However, this assumes that hunter-gatherers are free from modern stressors like busy schedules. Furthermore, it remains unclear whether these populations face similar health issues linked to insufficient sleep as modern societies do.

Research from extensive studies on sleep and health in industrialized societies indicates that the ideal sleep duration is likely less than eight hours. A study using brain scans and molecular measures found the optimal sleep range to be between 6.4 and 7.8 hours, depending on the person's sex and the organ being examined. Many studies also show that both insufficient and excessive sleep can lead to health problems, such as heart disease, stroke, cognitive decline, and obesity.

However, scientists are still uncertain whether too much sleep causes poor health or is merely an early sign of it.

These findings challenge the notion that everyone requires exactly eight hours of sleep. Current recommendations from the National Sleep Foundation in the US suggest that adults aged 26 to 64 should aim for seven to nine hours of sleep per day, though some individuals might thrive on six to ten hours. This range is a significant departure from the simplistic eight-hour rule.

Sleep is more than just the number of hours; it's about the timing and regularity of sleep. Modern sleep patterns are often delayed relative to the natural light-dark cycle. Artificial light is a primary reason for this, leading to delayed body clocks that control sleep and wakefulness. Irregular sleep, especially among shift workers and university students, is linked to poorer health. However, catching up on sleep on weekends can mitigate some of these issues, despite making sleep patterns less consistent.

The bottom line remains: the eight-hour rule is overly simplistic. People have varying sleep needs, and the timing of sleep is crucial. The key message is to ensure you get enough sleep when possible and avoid stressing over occasional sleepless nights.