Sleep hygiene is the controlling of "all behavioural and environmental factors that precede sleep and may interfere with sleep." It is the practice of following guidelines in an attempt to ensure more restful, effective sleep which can promote daytime alertness and help treat or avoid specific kinds of sleep disorders, and prevent the negative consequences of sleep deprivation.
The concept of “sleep hygiene” was first termed in 1977 by Paul Hauri, who published a list of behaviors intended to promote improved sleep. However, similar concepts are credited to Paolo Mantegazza, who published a related original book in 1864, and to Michael Perlis who wrote an article in The British Medical Journal in 1894. The 1991 publication of the International Classification of Sleep Disorders introduced the diagnostic category of Inadequate Sleep Hygiene. Over the past decades, specific sleep hygiene recommendations have been revised and expanded, as the medical field has made new advancements. For example, while avoiding sleeping pills may have been more appropriate in the 1970s, there are now non-habit-forming sleep aids.
Trouble sleeping and daytime sleepiness can be indications of poor sleep hygiene or sleep habits. The International Classification of Sleep Disorders-Revised (ICSD-R) states on page 74: "The importance of assessing the contribution of inadequate sleep hygiene in maintaining a preexisting sleep disturbance cannot be overemphasized." In the ICSD-R, the diagnosis inadequate sleep hygiene is classified as an extrinsic sleep disorder, code 307.41-1. To qualify for the diagnosis of inadequate sleep hygiene, an individual must first meet criteria for insomnia, and then exhibit one of the following behaviors:
- napping twice or more per week
- having a variable sleep-wake schedule
- spending excessive time in bed
- exercising shortly before bedtime
- engaging in activities that induce intense emotion shortly before bedtime
- frequently using bed for non-sleep-related activities
- using an uncomfortable bed for sleeping
- creating a bedroom environment that is not conducive to sleep (e.g. too hot or cold)
- engaging in activities that require high concentration shortly before bedtime
- recurrent intense thinking once in bed (e.g. planning or reminiscing)
Practice of sleep hygiene and knowledge of sleep hygiene practices can be assessed with the Sleep Hygiene Index, Sleep Hygiene Awareness and Practice Scale, Sleep Hygiene Practice Scale, or Sleep Hygiene Self-Test.
Sleep specialists and researchers have put forth a number of recommendations to improve sleep quality. These recommendations, listed below, are ordered such that the most commonly cited recommendations are listed higher, as reviewed by Paul Hauri 
Establishing a Sleep Schedule
- Do allow enough time for sleep. Most people need 7–9 hours of sleep each day.
- Avoid or curtail napping. While naps can helpful after sleep deprivation, under normal conditions naps are detrimental to nighttime sleep. The negative consequences of napping on sleep and performance have been found to depend on duration and timing, with shorter (less than 30 minutes) midday naps being less disruptive.
- Do wake up around the same time every morning. Modifying sleep schedule to involve regular sleep-wake times and a minimum of 7 hours of sleep has been associated with improved well-being and alertness during the day.
Engaging in the Right Activities
- Do exercise for about 20–30 minutes (preferably five to six hours before sleep), but avoid exercising within an hour before going to bed. People who exercise experience better quality of sleep than those that do not, however, exercising too late in the day can be activating and delay falling asleep.
- Do engage in relaxing activities prior to going to bed
- Avoid using your bed for any activities except sleep (or sex). Generally, spending less time in bed results in deeper and more continuous sleep.
- Avoid trying harder and harder to fall asleep if you are having great difficulty falling asleep, as this has been found to induce frustration and further prevent falling asleep. Instead do get out of bed and try something else for a brief amount of time.
- Avoid thinking about worries or anything emotionally upsetting during the time that you are getting ready to go to bed. For those with difficulty with this rule, do make a worry list 20 earlier in the evening in order to save these concerns for tomorrow.
- Avoid doing important work before bed or continuing to plan once in bed as this has been shown to delay falling asleep.
- Do increase your exposure to bright and natural light during the daytime. Then avoid bright light, or limiting exposure to blue light by the use of amber glasses or goggles, for two to three hours before bed. This helps promote a normal sleep-wake schedule.
- Do seek assistance from healthcare providers for continuing difficulties with sleep, since specific sleep disorders may require particular treatments.
Consuming Certain Foods and Substances
- Avoid nicotine, caffeine, and other stimulants within 4 hours of going bed. All of these substances activate neurobiological systems that maintain wakefulness of the mind and body, making sleep more difficult. Caffeine can be found in coffee, energy drinks, soda, tea, chocolate, and some pain relievers.
- Avoid alcohol close to bed time. Even though alcohol can induce sleepiness initially, the arousal your body experiences due to metabolizing the alcohol can disrupt your sleep, and it has been found to significantly fragment sleep.
- Avoid heavy meals several hours before bedtime. However, hunger can also disturb sleep, so do have a light snack before bed.
- Limit intake of liquids in the time leading up to bedtime
Creating a Comfortable Sleep Environment
- Do arrange a sleep environment that is very dark, quiet, and cool to facilitate falling asleep quickly and staying asleep. This can be accomplished with the aid of blackout curtains, eye masks, white noise machines, ear plugs, humidifiers, and fans and ensuring minimal interruptions by roommates and bed partners. Noises (especially irregular) interrupt sleep, even if sleepers do not remember waking up. Considering temperature, sleep has been shown to be disturbed when it is either too hot (above 75 °F) or too cold (below 41 °F)
- Do select a mattress, bedding, and pillows that are comfortable such that you also have enough room to stretch out. This includes changing your mattress once it has reached its recommended life expectancy
- Avoid having a visible bedroom clock from bed 
- Avoid leaving objects that you associate with stress (e.g. a laptop for work) near your sleeping space
Special Populations with Sleep Hygiene Difficulties
There are specific groups of individuals that due to conditions or circumstances are presented with additional barriers to sleep hygiene.
Sleep hygiene has become a central component of treatment for insomnia. Because individuals with insomnia have heightened difficulty with falling and staying asleep, using all sleep hygiene recommendations has shown to reduce the symptoms of insomnia.
College students have been identified as being at risk of engaging in poor sleep hygiene but also of being unaware of how the resulting sleep deprivation effects them. In general, because of the irregular weekly schedule and campus environment, college students are more likely to have variable sleep-wake schedules across the week, take naps, drink caffeine and/or alcohol near bedtime, and sleep in disruptive sleeping environments. Because of this, it is important to have sleep hygiene education on college campuses.
Similarly, shift workers have more difficulty maintaining a healthy sleep-wake schedule due to irregular job hours. Shift workers need to be more strategic about napping and drinking caffeine, as these practices may be necessary for work productivity and safety, but should be timed carefully. Because shift workers may need to sleep while other individuals are awake, additional sleeping environment changes should include reducing disturbances by turning off phones and posting sign on bedroom door to inform others when they are sleeping.
Due to symptoms of low mood and energy, individuals with depression are more likely to have the following behaviors that are counter to good sleep hygiene: taking naps during the day, consuming alcohol near bedtime, and consuming more caffeine during the day. In addition to sleep hygiene education, bright light therapy is a particularly useful treatment approach for individuals with depression. Not only can bright light therapy help establish a more normal sleep-wake schedule, but it also has been shown to be effective for treating depression directly, especially when related to seasonal affective disorder 
Individuals with any type of breathing difficulties – due to asthma or allergies – may need to make special changes to their bedroom environment. Difficulties with breathing while sleeping reduce ability to stay asleep and to get a restful sleep, and it is therefore important to consider how to reduce allergy or asthma triggers. This might include purchasing hypoallergenic bedding, not allowing pets in the bedroom, using de-humidifiers, and especially avoiding exercise in the hours before bedtime.
For individuals who experience physical pain – chronic or situational – they have to be particularly careful about consumption of medications and substances. Many pain-relieving substances – ibuprofen, intense pain killers, alcohol – have chemical effects that can induce either sleepiness or wakefulness, and therefore individuals managing their pain should consider the timing of these medications with their sleep-wake schedule.
Results of Poor Sleep Hygiene
Knowledge of sleep hygiene practices has been found to relate to actual sleep hygiene practices, which ultimately relates to quantity and quality of one’s sleep, and this holds true for those with and without sleeping disorders. Sleep hygiene is associated with subjective sleepiness and actual sleep deprivation across cultures. There are correspondingly a number of cognitive, emotional, social, and physical consequences of such sleep deprivation and poor sleep quality.
Doctors and clinicians who advise sleep hygiene strategies for patients and families have lists of suggestions which may include advice about timing of sleep and food intake in relationship to it, exercise, sleeping environment, etc. Which items are suggested for which patients are selected by the clinician, depending on knowledge of the individual situation; the counselling is presented as a form of patient education. Re-education involves a combination of advice about homeostatic, adaptive and circadian aspects of sleep control, how to avoid sleep deprivation, and how to respond to unwanted awakenings from sleep if these occur. As the second edition of the ICSD (ICSD2, 2005) points out, the "sleep disruptive effects of poor sleep hygiene are often obvious to others, but the patients show little insight into this fact."
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