The Internet is full of sleep myths with no basis behind them – for example it’s often said that we sleep in fixed phases of 90 minutes, so we should wake up at a multiple of 90 minutes - whereas in practice these phases vary between 90 and 128 minutes. On this page the sleep tips are all backed up by solid evidence.
The importance of sleep
Lack of sleep has a variety of damaging effects including reducing our daytime performance, contributing to obesity, reducing our ability to learn and as we all know, it can make us moody!Belenky G, Wesensten NJ, Thorne DR, et al. Patterns of performance degradation and restoration during sleep restriction and subsequent recovery: a sleep dose‐response study. Journal of Sleep Research. 2003;12(1):1–12.Taheri S. The link between short sleep duration and obesity: we should recommend more sleep to prevent obesity. Archives of Disease in Childhood. 2006;91(11):881 –884.Stickgold R. Sleep-dependent memory consolidation. Nature. 2005;437(7063):1272–1278. Never mind the estimate that 100,000 car crashes in the USA alone are the direct result of driver fatigue each year.Royal Society for the Prevention of Accidents, 2001, Driver fatigue and road accidents. It has also been shown that too little (though also too much) sleep increases the risk of death from heart problems.Ferrie JE, Shipley MJ, Cappuccio FP, et al. A Prospective Study of Change in Sleep Duration: Associations with Mortality in the Whitehall II Cohort. Sleep. 2007;30(12):1659–1666. Needless to say, sleep is important.
A brief description of sleep
When we’re relaxed and peaceful and our eyes are closed, the brain goes into an ‘alpha’ state - a particular set of brainwaves that can be detected with a brain EEG. As we start falling asleep these alpha waves are initially replaced by slightly slower ‘theta’ waves, with spikes called sleep spindles. This phase lasts for 10-25 minutes, and at this point if you wake up often you wouldn’t even realise you’ve started to fall asleep. It is also during this period that ‘hypnic jerks’ occur –the falling sensation that many people feel as they’re falling asleep – and which can be exacerbated by stress or anxiety.Barral, J. (2005). When dreams mix up with reality. Stanford.edu
Much slower delta waves then begin to take over, forming our deepest sleep, during which certain people sleep-walk or sleep-talk. As opposed to the REM (rapid eye-movement) – sleep that we’ve all heard of, this is called NREM sleep (non rapid eye-moment). About 50-70 minutes into the night the first REM period begins. During REM periods we have an increase in brain activity and most of our dreaming occurs.
During the night we cycle around 4-5 times between NREM and REM sleep. In the earlier cycles REM can be for as short as 1-5 minutes of the cycle, but can be as long as an hour in later cycles. Sleep cycle length varies person to person (depending on factors such as the person’s fitness), but is on average 90-128 minutes.Trinder J, Stevenson J, Paxton SJ, Montgomery I. Physical Fitness, Exercise, and REM Sleep Cycle Length. Psychophysiology. 2007;19(1):89–93.Schulz H, Dirlich G, Balteskonis S, Zulley J. The REM-NREM sleep cycle: renewal process or periodically driven process? Sleep. 1980;2(3):319–328.Le Bon O, Staner L, Rivelli SK, Hoffmann G, Pelc I, Linkowski P. Correlations Using the NREM-REM Sleep Cycle Frequency Support Distinct Regulation Mechanisms for REM and NREM Sleep. J Appl Physiol. 2002;93(1):141–146.
Upon wake the brain doesn’t immediately enter a fully alert state, and goes through a phase of sleep inertia which can last for over half an hour. During this phase decision making and reaction times are impaired.Bruck D, Pisani DL. The effects of sleep inertia on decision‐making performance. Journal of Sleep Research. 2002;8(2):95–103.1. Jewett ME, Wyatt JK, Ritz‐De Cecco A, Khalsa SB, Dijk D-J, Czeisler CA. Time course of sleep inertia dissipation in human performance and alertness. Journal of Sleep Research. 2008;8(1):1–8.
In building the app we carried out a large amount of research on the science of sleep, here are some tips we've put together to help out our users.
Don’t drink coffee, tea or cola just before bed. These all contain caffeine which unsurprisingly has a negative impact on sleep quality, increasing both the length of time to fall asleep, decreasing the length of the sleep itself and reducing the depth of sleep.Březinová V. Effect of caffeine on sleep. Br J Clin Pharmacol. 1974;1(3):203–208. Hindmarch I, Rigney U, Stanley N, Quinlan P, Rycroft J, Lane J. A naturalistic investigation of the effects of day-long consumption of tea, coffee and water on alertness, sleep onset and sleep quality. Psychopharmacology. 2000;149(3):203–216. Landolt HP, Dijk D-J, Gaus SE, Borbély AA. Caffeine reduces low-frequency delta activity in the human sleep EEG. Neuropsychopharmacology. 1995;12(3):229–238. It’s even been shown that caffeine at the start of the day can have a negative effect on sleep that night.Landolt H-P, Werth E, Borbély AA, Dijk D-J. Caffeine intake (200 mg) in the morning affects human sleep and EEG power spectra at night. Brain Research. 1995;675(1–2):67–74.
Don’t partake in exciting or stressful activities too late in the evening. For example a study in Japan found that playing a shooting computer game up until 15 minutes before bed caused participants to take longer to fall asleep, and to have 25% reduced REM sleep time.Higuchi S, Motohashi Y, Liu Y, Maeda A. Effects of playing a computer game using a bright display on presleep physiological variables, sleep latency, slow wave sleep and REM sleep. Journal of Sleep Research. 2005;14(3):267–273. (they also tested if the brightness of the screen made a difference - it didn't)
As we’re all always told, exercise is good – and sleep is no exception. Studies have found moderate links between exercise and sleep quality.Driver HS, Taylor SR. Exercise and sleep. Sleep Medicine Reviews. 2000;4(4):387–402.Youngstedt SD, O’Connor PJ, Dishman RK. The effects of acute exercise on sleep: a quantitative synthesis. Sleep. 1997;20(3):203–214.Singh NA, Clements KM, Fiatarone MA. A randomized controlled trial of the effect of exercise on sleep. Sleep. 1997;20(2):95–101. A study on the effects of exercise just before bed found it didn't actually harm the quality of sleep.Youngstedt SD, Kripke DF, Elliott JA. Is sleep disturbed by vigorous late-night exercise? Med Sci Sports Exerc. 1999;31(6):864–869.
It may sound obvious, but going to the toilet before going to bed reduces the chances of needing to get up and interrupt sleep during the night.
Tryptophan, found in milk (as well as most protein-based foods) has been proven to increase non-REM sleep, though it’s unproven as to whether it’s effective in the context and quantities found in milk - milk has small quantities of tryptophan and also contains other proteins that could stop the tryptophan being able to reach the brain.Wurtman RJ, Wurtman JJ, Regan MM, McDermott JM, Tsay RH, Breu JJ. Effects of Normal Meals Rich in Carbohydrates or Proteins on Plasma Tryptophan and Tyrosine Ratios. Am J Clin Nutr. 2003;77(1):128–132.
A study in Japan showed that a hot bath before bed helped reduce time to fall asleep, with a hot footbath proving to be just as effective as a full bath. Kanda K, Tochihara Y, Ohnaka T. Bathing before sleep in the young and in the elderly. European Journal of Applied Physiology and Occupational Physiology. 1999;80(2):71–75.
There’s no proof that eating before bed has either positive or negative effects on sleep, though it can exacerbate heartburn as the stomach loses the element of gravity to keep the acids down.
As most of us have experienced, alcohol has extensive effects on sleep. Large amounts of alcohol disturb sleep, but lower doses (eg a small glass of wine) can be beneficial, bearing in mind that people quickly become tolerant to regular consumption after which it’s no longer effective.Roehrs T, Roth T. Sleep, sleepiness, and alcohol use. Alcohol Research & Health. 2001;25(2):101–109.
For most people the body-clock works on a 24.18 hour cycle (not 25 hours as was thought for a long time), therefore if you consistently go to bed the same time every night and get up the same time every morning, the body can operate close to it’s natural daily cycle and this helps ensure the highest quality of sleep.Czeisler CA, Duffy JF, Shanahan TL, et al. Stability, Precision, and Near-24-Hour Period of the Human Circadian Pacemaker. Science. 1999;284(5423):2177–2181.
Becoming hungry during the night can disrupt sleep Jacobs BL, McGinty DJ. Effects of food deprivation on sleep and wakefulness in the rat. Experimental Neurology. 1971;30(2):212–222. so a light bed-time snack can be beneficial.
Some people take Melatonin before going to sleep. Melatonin is a hormone involved in the sleep-wake cycle, its level in the body varies between the day and night. It’s present in some food and plants, and available over the counter in natural health shops in the US. Two thorough reviews of studies on melatonin both showed it results in a small decrease in time to fall asleep and increased sleep efficiency. They also concluded that it’s a relatively safe drug. Buscemi N, Vandermeer B, Pandya R, et al. Melatonin for treatment of sleep disorders. Evid Rep Technol Assess (Summ). 2004;(108):1–7. Brzezinski A, Vangel MG, Wurtman RJ, et al. Effects of exogenous melatonin on sleep: a meta-analysis. Sleep Medicine Reviews. 2005;9(1):41–50. The best time to take Melatonin is about 8pm, rather than just before bed. Tzischinsky O, Pal I, Epstein R, Dagan Y, Lavie P. The importance of timing in melatonin administration in a blind man. Journal of Pineal Research. 1992;12(3):105–108.
Stimulus control therapy attempts to make a mental association between the bed and sleep via a set of rules. These rules are: a) lie down in bed only when sleepy, b) do not use the bed for anything except sleep, c) if you can’t sleep then immediately go into another room and do a different activity until sleepy, d) get up the same time every morning however much sleep you had during the night. It has not been shown to be effective for everyone, but it has been shown to be effective for some. Bootzin R, Epstein D, Wood J. Stimulus control instructions. In: Hauri P, editor. Case studies in insomnia. New York: Plenum Press; 1991. pp. 19–28.
An alternative technique for those with difficulty falling asleep is called paradoxical intention – try to stay awake as long as possible. By removing the fear of not being able to sleep, this can paradoxically help you fall asleep faster. Ascher LM, Turner RM. Paradoxical intention and insomnia: an experimental investigation. Behaviour Research and Therapy. 1979;17(4):408–411.
For people woken by sounds during the night, an effective strategy can be to go to sleep with some constant background noise that masks the outside sounds - for example a fan, or a recording of white noise (ie a constant whooshing sound). A study showed people were much less likely to be woken by a recording of a mixture of hospital noises and white noise than the hospital noises alone. Stanchina ML, Abu-Hijleh M, Chaudhry BK, Carlisle CC, Millman RP. The influence of white noise on sleep in subjects exposed to ICU noise. Sleep Medicine. 2005;6(5):423–428. We have included several types of background noise in the Rise UP! Radio/Alarm app.
An alternate sound to fall asleep to is ‘binaural beats’. These are stereo sounds that pulse in time in a way designed to bring brain-waves to a specific rhythm. Though research result are mixed, there is some indicating that it may have a positive effect. As such we have included binaural beats as a sleep option in Rise UP! Radio/Alarm.
Whilst some believe in trying to align their waking time with their REM sleep cycle (for example by assuming that the sleep cycle is always 90 minutes, so waking on a multiple), the body's cycle times vary too much day-to-day and between individuals for this to be effective.Schulz H, Dirlich G, Balteskonis S, Zulley J. The REM-NREM sleep cycle: renewal process or periodically driven process? Sleep. 1980;2(3):319–328. Le Bon O, Staner L, Rivelli SK, Hoffmann G, Pelc I, Linkowski P. Correlations Using the NREM-REM Sleep Cycle Frequency Support Distinct Regulation Mechanisms for REM and NREM Sleep. J Appl Physiol. 2002;93(1):141–146. The use of motion sensors (known to sleep scientists as actigraphy) is another technique to attempt to trigger an alarm in sync with the body sleep cycle. However in practice the use of motion sensors are not thought to be able to distinguish the different stages of sleep.Tryon WW. Issues of validity in actigraphic sleep assessment. Sleep. 2004;27(1):158–165. Therefore it is best to simply target 7-8 hours of sleep a night, which has shown to be best for health.Ferrie JE, Shipley MJ, Cappuccio FP, et al. A Prospective Study of Change in Sleep Duration: Associations with Mortality in the Whitehall II Cohort. Sleep. 2007;30(12):1659–1666. One option is an alarm that very slowly fades in, as we are more sensitive to sounds during lighter sleep. Rechtschaffen A, Hauri P, Zeitlin M. Auditory Awakening Thresholds in REM and NREM Sleep Stages. Perceptual and Motor Skills. 1966;22(3):927–942.
Certain individuals (particularly the elderly) have issues with maintaining deep sleep states over a long period of time. For these people, splitting the night-time and nap sleep provides a larger amount of total deep sleep over the 24-hour period.Carskadon MA, Brown ED, Dement WC. Sleep fragmentation in the elderly: relationship to daytime sleep tendency. Neurobiol. Aging. 1982;3(4):321–327.
Ambient temperature can affect quality of sleep. Different people have different preferences for temperature, though there's a tendency for people to prefer temperatures slightly lower than comfortable daytime temperature. Haskell E., Palca J., Walker J., Berger R., Heller H. The effects of high and low ambient temperatures on human sleep stages. Electroencephalography and Clinical Neurophysiology. 1981;51(5):494–501.
Getting less than a full-night of sleep results in an accumulating sleep debt. A study at Stanford revealed that with sleep limited to 5 hours per night, sleepiness reached a plateau after 4 days, with full recovery after 10 hours of sleep (though other studies have shown it take several days for full recovery).Carskadon MA, Dement WC. Cumulative Effects of Sleep Restriction on Daytime Sleepiness. Psychophysiology. 2007;18(2):107–113.Belenky G, Wesensten NJ, Thorne DR, et al. Patterns of performance degradation and restoration during sleep restriction and subsequent recovery: a sleep dose‐response study. Journal of Sleep Research. 2003;12(1):1–12.
Given that light can disturb our sleep, and the timing which we’re exposed to light can shift the body clock, it is best to avoid bright light during the evening and night. Dawson D, Campbell SS. Time exposure to bright light improves sleep and alertness during simulated night shifts. Sleep: Journal of Sleep Research & Sleep Medicine. 1991;14(6):511–516. Friedman L, Zeitzer JM, Kushida C, et al. Scheduled bright light for treatment of insomnia in older adults. J Am Geriatr Soc. 2009;57(3):441–452.
Research has indicated that mobile phone transmission frequencies can have an effect on the brainwaves during sleep.Schmid MR, Loughran SP, Regel SJ, et al. Sleep EEG alterations: effects of different pulse‐modulated radio frequency electromagnetic fields. Journal of Sleep Research. 2011;21(1):50–58. No adverse effects were seen on performance tests performed after wake-up, but some may want to keep their phone on airplane mode during the night. For this reason Rise UP! Radio/Alarm has a feature that enables airplane mode in the evening, and disables it a few minutes before the alarm goes off in the morning.
Bright light after waking can be effective at bringing about alertness, especially for those that need to wake early.Leproult R, Colecchia EF, L’Hermite-Balériaux M, Van Cauter E. Transition from Dim to Bright Light in the Morning Induces an Immediate Elevation of Cortisol Levels. JCEM. 2001;86(1):151–157.
There are alternatives to be woken up by an audio alarm. Some people find that sunrise alarm clocks, which have a bright light that gradually fades in at the wake-up time, are effective at gradually waking them up.
Research into how to wake people in case of fire emergencies has shown that a pulsed alarm sound at 520hz is more effective at waking people than alarms at higher frequencies.Thomas, I. and Bruck, D. Strobe lights, pillow shakers and bed shakers as smoke alarm signals. Ninth International Symposium on Fire Safety Science , 21-26 September 2008, Karlsruhe, Germany. Schmid MR, Loughran SP, Regel SJ, et al. Sleep EEG alterations: effects of different pulse-modulated radio frequency electromagnetic fields. Journal of Sleep Research. 2012;21(1):50–58. For this reason Rise UP! Radio/Alarm includes a 520hz alarm sound.
The benefits of naps have been demonstrated in many studies for both those who haven’t had enough sleep and those who have had a full night of sleep (34).Gillberg M. The effects of two alternative timings of a one-hour nap on early morning performance. Biol Psychol. 1984;19(1):45–54. There is no single ideal time to take a nap – the best time depends on a variety of factors such as quality of sleep during the previous night, individual sleep need and how awake you are. Milner CE, Cote KA. Benefits of napping in healthy adults: impact of nap length, time of day, age, and experience with napping. Journal of Sleep Research. 2009;18(2):272–281.
Ideal nap length for most people is about 20 minutes total – about 10 minutes to fall asleep, and 10 minutes of actual sleep. This is long enough for some delta-wave brain activity to occur and to therefore get benefit from the nap, but short enough to avoid sleep inertia (feeling groggy after waking). Milner CE, Cote KA. Benefits of napping in healthy adults: impact of nap length, time of day, age, and experience with napping. Journal of Sleep Research. 2009;18(2):272–281. Brooks A, Lack L. A brief afternoon nap following nocturnal sleep restriction: which nap duration is most recuperative? Sleep. 2006;29(6):831–840. Tietzel AJ, Lack LC. The short-term benefits of brief and long naps following nocturnal sleep restriction. Sleep. 2001;24(3):293–300. 26 minutes is often quoted in the media as an ideal nap length, but the study this came from didn't include the time to fall asleep in the 26 minute figure, and didn't actually compare different nap lengths. Rosekind, MR, et al. Effects of Planned Cockpit Rest on Crew Performance and Alertness in Long-Haul Operations. NASA Technical Memorandum No. 108839.
Drinking coffee just before a short nap improves the level of alertness immediately after waking – as the caffeine doesn’t kick in for up to 30 minutes it doesn’t interfere with the nap itself. Reyner LA, Horne JA. Suppression of sleepiness in drivers: Combination of caffeine with a short nap. Psychophysiology. 2007;34(6):721–725.