Adults may not need eight hours of sleep every night to stay healthy, according to a new study reported by the New York Post.
Researchers challenged the long-held belief that a continuous eight-hour night of rest is an essential requirement for the human body. Findings indicate that optimal sleep duration varies significantly from person to person depending on individual health and biological factors.
Evidence from pre-industrial societies suggests that human sleep patterns were historically far more flexible. An analysis of communities in Tanzania, Namibia, and Bolivia revealed that residents slept an average of 5.7 to 7.1 hours per day. These individuals typically woke at dawn and did not make up for shorter night sleep by taking daytime naps.
A separate analysis of pre-industrial populations found that adults slept an average of about 6.4 hours each night. Pre-industrial societies rely primarily on agriculture, foraging, or traditional manual labor without access to modern electrical lighting.
Impact of artificial light on circadian rhythm
Modern lifestyle habits differ substantially from natural daylight patterns. Researchers noted that artificial light sources, including electric lamps, computer screens, and smartphones, shift the human biological clock and prompt people to go to bed later.
The human internal biological clock, often referred to as the circadian rhythm, controls sleepiness and alertness throughout the 24-hour day in response to environmental light cues.
Optimal sleep duration and organ health
Large-scale research indicates that the ideal sleep duration for maintaining overall health can be less than eight hours. In one study examining brain function and organ health, researchers determined that optimal sleep ranges between 6.4 and 7.8 hours, depending on sex and physical condition.
Experts emphasized that eight hours of rest is neither inherently harmful nor insufficient. While eight hours remains ideal for some individuals, others may naturally require more or less sleep to feel fully restored.
National Sleep Foundation guidelines for adults
Official guidance from the National Sleep Foundation recommends that adults aged 26 to 64 obtain 7 to 9 hours of sleep per night. However, individual requirements can legitimately vary from about 6 to 10 hours.
The National Sleep Foundation is a non-profit organization headquartered in the United States that publishes health standards regarding sleep hygiene and sleep disorders.
Specialists noted that sleep quality, regularity, and post-wakefulness energy levels are far more critical than aiming for a rigid hours target. Feeling persistent exhaustion after eight hours of sleep may indicate an underlying need for a different sleep duration.
Ageing and melatonin production
Specialists previously explained that older adults frequently sleep fewer hours due to shifting biological rhythms. As people age, the secretion of melatonin begins earlier in the evening, leading older adults to experience drowsiness earlier in the night.
Melatonin is a hormone produced by the brain's pineal gland that helps synchronize circadian rhythms and signals time for sleep.
Separately, cardiologists have cautioned against improper sleeping positions, warning that certain sleep postures can be harmful to physical health.
