Is 8-Hour Sleep Unnatural for Humans?

Check out this answer from Consensus:

The notion that eight hours of sleep is universally optimal for health is increasingly being questioned by scientific research. Studies suggest that seven hours of sleep may be more beneficial for reducing mortality risk, while both shorter and longer sleep durations can have adverse health effects. Sleep deprivation, in particular, has been shown to increase food intake and impair cardiovascular function. Therefore, while eight hours of sleep may be a good guideline, individual sleep needs can vary, and a one-size-fits-all recommendation may not be appropriate.

In summary, the idea that eight hours of sleep is natural and necessary for all humans is not supported by current research. Instead, a more personalized approach to sleep duration, taking into account individual health and lifestyle factors, may be more beneficial.

The conventional wisdom suggests that eight hours of sleep per night is optimal for good health. However, recent research challenges this notion, indicating that the ideal sleep duration may vary and that both shorter and longer sleep durations can have significant health implications. This article explores whether an 8-hour sleep duration is natural for humans by examining various studies on sleep duration and its effects on health.

The 8-Hour Sleep Myth

The belief that eight hours of sleep is necessary for optimal health is widespread. However, a prospective study of sleep duration and mortality risk in women found that the lowest mortality risk was among those who slept seven hours per night. The study, which followed 82,969 women over 14 years, revealed that sleeping less than six hours or more than seven hours was associated with an increased risk of death. Specifically, the relative mortality risk for sleeping eight hours was 1.12, compared to the reference group of seven hours2. This suggests that the commonly recommended eight hours of sleep may not be the most beneficial for everyone.

Effects of Sleep Deprivation

While the ideal sleep duration may be less than eight hours, it is clear that insufficient sleep can have detrimental effects. A study on acute partial sleep deprivation in healthy men showed that reduced sleep led to increased food intake and higher levels of hunger. Participants who slept only four hours consumed 22% more calories the following day compared to when they had eight hours of sleep. Additionally, their physical activity levels were higher despite feeling sleepier1. This indicates that sleep deprivation can disrupt normal physiological functions, potentially leading to weight gain and other health issues.

Cardiovascular Health and Sleep

Sleep duration also plays a crucial role in cardiovascular health. Research on the effects of sleep restriction on endothelial function found that moderate sleep restriction (sleeping 5.1 hours per night) caused significant impairment in endothelial function, a key factor in cardiovascular health. The study demonstrated that sleep restriction led to a marked decrease in flow-mediated brachial artery vasodilatation, indicating endothelial dysfunction3. This finding underscores the importance of adequate sleep for maintaining cardiovascular health, although the optimal duration may vary.

Is 8-hour sleep unnatural for humans?

Doug Henry has answered Extremely Unlikely

An expert from University of North Texas in Cultural Anthropology, Medical Anthropology, Sleep Research

There’s nothing “natural” or “unnatural” about our sleep. Such terms imply a kind of human universality for “appropriate” sleep; this doesn’t exist in a global context. “Normative” sleep behavior, sleep hygiene, and bedtime rituals are far from universal, and can vary significantly among and across different societies and cultures. Medical anthropological and sociological studies, for example, have shown how sleep patterns and disorders take place within social, cultural, and environmental contexts. Cross-cultural research into the anthropology of sleep has focused on the adaptivity of various sleeping positions to the social and physical environments, parent-infant co-sleeping arrangements and risk of SIDS, the effects of social class and economic recession on insomnia, and the distinctive sleep patterns of non-Western societies, which can vary in terms of individual vs. partnered sleep, bodily contact, background noise, sleep duration, prevalence of napping, and the daily episodic nature or “phases” of sleep.