Sleep myths and facts
Popular beliefs about sleep, checked against the studies. Tap a card to reveal the answer.
Does counting sheep help you fall asleep?
In a University of Oxford study of 50 poor sleepers, people who pictured a calm scene (a beach, a waterfall) fell asleep sooner than those who counted sheep. Counting may be too monotonous to occupy the mind… and not pleasant enough to calm it.
Source: Harvey A. G., Payne S., Behaviour Research and Therapy, 2002 (40:267-277)
Does working out in the evening keep you up?
A review of 23 studies found no negative effect of evening exercise on sleep, if anything the opposite. One caveat: a workout much more intense than usual seemed to make sleep slightly less efficient, a signal that's still weak.
Source: Stutz J. et al., Sports Medicine, 2019 (49:269-287)
Do screens at night delay sleep?
In a Harvard study, reading on a light-emitting tablet instead of a paper book pushed back falling asleep by about ten minutes and made people feel less alert the next morning. But the study only included 12 people, and what you're looking at probably matters as much as the light.
Source: Chang A.-M. et al., PNAS, 2015 (112:1232-1237)
Does the full moon disturb sleep?
A Swiss study observed shorter deep sleep around the full moon in 33 volunteers who slept without seeing the sky. But a new analysis with more than 1,200 volunteers didn't find that effect. Still an open question, and that's what makes it fascinating.
Source: Cajochen C. et al., Current Biology, 2013; Cordi M. et al., Current Biology, 2014
Do you need 8 hours of sleep, not a minute less?
Scientific societies talk about a range instead, 7 to 9 hours for most adults, and needs vary from one person to the next. Feeling rested during the day is a good guide, much more than the clock.
Source: Hirshkowitz M. et al., Sleep Health, 2015
Does a glass of warm milk help you sleep?
People often point to the tryptophan in milk, but the amounts involved are small. A review of 14 studies found mostly positive effects, but they varied widely from one study to another, and the review was funded by the dairy industry. On the other hand, a gentle gesture repeated every evening can help you transition into the night. That's the power of rituals.
Source: Komada Y. et al., International Journal of Environmental Research and Public Health, 2020
These guides offer wellbeing information and do not replace a doctor's advice.
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