Sleep quality

Sleep is considered essential for human health and well-being. Good sleep is necessary to help the body recover from the physical and psychological fatigue it suffers during the day and help it to restore energy to maintain its functions. During sleep, the brain recovers energy, memories and impressions are processed and new knowledge is stored. People are ready to face the challenges of a new day with the power of a good night's sleep. A comfortable sleep is also necessary for high productivity during the day.

Defining sleep

Sleep can be defined as: 'a natural periodic state of rest for the mind and the body, in which the eyes usually close and the consciousness is totally or partially lost, so that the body's movement and reaction to external stimuli are reduced. During sleep the brain in humans and other mammals undergoes a characteristic cycle of brainwave activity that includes intervals of dreaming'.

"Sleep is the golden chain that ties health and our bodies together."   — Thomas Dekker

Facts about sleeping

People spend one-third of their life sleeping, 12–14 hour per day during infancy and 7–8 hours per day during adulthood, so sleep is essential to human health and well-being.

Sleep quality

Sleep quality is defined as an individual's self-satisfaction with all aspects of the sleep experience. Sleep quality has four attributes: sleep efficiency, sleep latency, sleep duration, and wake after sleep onset.

  • Sleep efficiency: the percentage of time a person sleeps, in relation to the amount of time a person spends in bed. For example, if a person spends 8 hours in bed, at least 6.4 hours or more should be spent sleeping to achieve an 80% or greater sleep efficiency.  Most healthy and young adults have sleep efficiencies above 90%.
  • Sleep latency: the amount of time it takes a person to fall to sleep. Normal sleep latency is 5-15 minutes.  Sleep latency less than five minutes may suggest some degree of excessive sleepiness. Sleep latency greater than 15 minutes may suggest some difficulty with sleep initiation.
  • Sleep duration: 7-9 hours is recommended for young adults and adults, and 7-8 hours of sleep is recommended for older adults.
  • Wake after sleep onset: a statistic used in sleep studies to determine the amount of time a person spends awake, starting from when they first fall asleep to when they become fully awake and do not attempt to go back to sleep. The normal unit of measure for this statistic is minutes.

How do we sleep? 

There are four stages of sleep that make up each sleep cycle. Each sleep cycle lasts about 90-120 minutes; thus, a person should have 4-5 cycles of sleep each night.

Sleep towards the healthy living

Sleep is essential for our mental and physical health and therefore our overall quality of life. Chronic sleep deficiency can affect brain function and heart health, as well as increase the risk of certain health conditions, such as diabetes, obesity, kidney disease and stroke.

Antecedents include:

  • Physiological (e.g. age, circadian rhythm, body mass index, NREM, REM)
  • Psychological (e.g. stress, anxiety, depression)
  • Environmental factors (e.g. room temperature, television/device use)
  • Family and/or social commitments

Good sleep quality has positive effects such as feeling rested, normal reflexes, and positive relationships. Poor sleep quality consequences include fatigue, irritability, daytime dysfunction, slowed responses, and increased caffeine/alcohol intake.

Bedroom temperatures and air quality

Preferred bedroom temperatures vary widely as a function of sleepwear, bedcover insulation and drape, and mattress insulation, with a trade-off between what is thermally comfortable for sleep and for other activities in the bedroom while not asleep.

The bedroom should have door and windows, for privacy and energy conservation and air supply. Some studies show that almost half of the bedrooms have a TV set and computer, which contributes to pollution of the indoor air.

The deep breathing that happens during a persons sleep cycle can get disrupted from allergens like ragweed, dust, and mould and can make allergy or asthma symptoms even worse.

Human body and skin naturally lose moisture when a person sleeps. The indoor air must have a good humidity level between 45-60% in order to avoid waking up with excessively dry skin and dry nasal passages.

The bedroom should be pollutant-free zone and properly ventilated. Improvements can be made to the bedroom by keeping computers, printers, and other electronics in a separate room and by using non-chemical air fresheners like bi-product-free candles or diffused oils.

Fun facts about sleeping

Humans spend about one-third of their lives sleeping, whereas cats spend roughly two-thirds of their lives sleeping. Other species, like koalas and bats, may sleep for up to 22 hours a day.

Newborns require 14 to 17 hours of sleep per day, whereas teens require 8 to 10 hours per night. Most individuals require 7 to 9 hours of sleep each night.

Sleep deprivation can be detrimental to one's health. Just 24 hours of sleep deprivation can result in mood changes, difficulties working, and impaired perception.

Energy levels naturally tend to drop at two points during the day: 2:00 a.m. and 2:00 p.m. This explains why some people experience post-lunch tiredness.

The right indoor climate for a good sleep 

For years, sleep researchers have been recommending that bedroom temperatures range between 19°C and 21°C. Some people even prefer 18°C because they will have thicker blankets, pyjamas and warm linen.

Also, the preferred bedroom air temperatures vary greatly among individuals as in how unconsciously they manipulated the bed linen during sleep. Still, women sometime choose up to 3ºC higher room temperature than men and this decision can be influenced by the type of sleeping clothes. However, it is difficult to fall asleep and to stay asleep when the bedroom is too cold or too hot.

The recommended design values for heating are 20°C and for cooling 26°C (variations for classes I, II, III).

Having a sleeping environment that is draught free and has the right humidity level will also make a big difference to a persons sleep quality. The humidity level should be around 40-50%. 

The airflows should be based on the activity and type of the room. Airflow and air change levels should not cause unpleasant draught. A draught while you're sleeping can actually contribute to irritated eyes, and muscle stiffness. Also the room needs to be dark and noise levels need kept to a minimum.

Many studies indicate that the quality of sleep differs according to the air quality in bedrooms. If the carbon dioxide level exceeds 1,200 parts per million (ppm), the indoor air quality becomes bad enough to be reflected by the occupants and their productivity and focus may be affected negatively.

Good sleep is the building block for the day

Good quality sleep is necessary to help the body recover and restore energy in order to maintain its many important functions as well as to cope with everyday life. This article explores the quality of sleep in relation to the indoor climate in a bedroom — what measures may be taken to ensure the right indoor climate in a bedroom to further secure a good night's sleep?


Read our Update&Insight 'Good sleep is the building block of the day'

Impact of indoor air quality on next-day performance

The effects of bedroom air quality on sleep and next-day performance in offices are often studied. Conclusions have shown that when the air quality improves, the occupants reported that the air in their bedroom was fresher and their quality of sleep improved.

The occupants also felt less sleepy and more focused that coming day. Their logical thinking improved and they worked more effectively in the days that followed the nights when their bedroom was properly ventilated.

The results showed the greatest improvements in areas that explored how people used information for strategic decisions and how they plan, stay prepared, and strategise, especially in crisis situations.

After sleeping in well-ventilated bedrooms, the occupants had better enthusiasm and concentration on their work.

The increased ventilation rate as well as increased perceived air quality has a positive impact on the performance of office workers. In some cases, the overall performance on the next day after a good night's sleep may be improved from 2% to 20%.

Yet, higher indoor temperatures and relative humidity below 20% have a negative effect on the eyes, resulting in a lower work rate. Insufficient air circulation indoors may also cause other symptoms such as a sore throat, morning headaches or irritation of the eyes. 

People in homes and offices differ from occupants in other types of buildings, such as, hotels or schools. The people in homes want to have more control over the indoor climate, yet there may be problems with quality maintenance. The occupants in hotels expect high comfort, mainly because they need to focus on work performance the next day if on a business trip.

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Watch: Performance research on sleep, hunger and driver vigilance

Lecturer: David P. Wyon

Webinar recording from Swegon Air Academy, 2015. 

In this video you will find information on how other factors affect peoples' performance during a 24 hour cycle, including:

  • Bedroom ventilation rate and sleep quality
  • Poor sleep and next-day performance
  • Breakfast and morning performance
  • Lunch and afternoon performance
  • Vehicle T and driver vigilance
  • Airborne dust and driver vigilance

Easy steps to improve your sleep hygiene

  • Keep a consistent sleep schedule. Get up at the same time every day, even on weekends or during vacations.
  • Set a bedtime that is early enough for you to get at least 7-8 hours of sleep.
  • Don't go to bed unless you are sleepy. If you don’t fall asleep after 20 minutes, get out of bed.
  • Go do a quiet activity without a lot of light exposure. It is especially important to avoid electronics.
  • Establish a relaxing bedtime routine. Use your bed only for sleep and intimacy.
  • Make your bedroom quiet and relaxing. Keep the room at a comfortable, cool temperature. Limit exposure to bright light in the evenings.
  • Turn off electronic devices at least 30 minutes before bedtime.
  • Don't eat a large meal before bedtime. If you are hungry at night, eat a light and healthy snack.
  • Exercise regularly and maintain a healthy diet.
  • Avoid consuming caffeine in the afternoon or evening.
  • Avoid consuming alcohol before bedtime.
  • Reduce your fluid intake before bedtime.


Sleep quality in hotels 

Most people spend their nights in the bedrooms of their homes, which gives them the best comfort thanks to the familiarity. Sometimes they need to sleep in other places like hotels.

There are more factors to consider regarding the quality of sleep in hotels when compared to bedrooms in homes, as hotels can often feel unfamiliar and uncomfortable. Most of the research suggests that the quality of sleep in hotels is affected by individual differences (age, gender), hotel characteristics (room and bed characteristics), as well as environmental characteristics (traffic noise, neighbourhood quality). Also, jet lag and distances may have detrimental effects on sleep quality due to spatial change.

The ventilation system in hotels should be quiet and draught-free to ensure a good night's rest for hotel guests with a temperature of 20°C in the winter and 25°C in the summer. The system must supply a room with approximately 40 m³/h per person of well-filtered outdoor air. It must also guarantee the highest level of hygiene.

The indoor air quality in the hotel is directly related to the amount of fresh air supplied to the room and the levels of pollutants and odorous substances in the room. Fresh airflow is then based on how many guests are in the room and how many odorous substances are emitted by devices and equipment in the room.

Since there are many factors, the best system for hotel is demand-controlled ventilation (DCV) to achieve a good indoor climate for variable spaces and hotels' needs.

No wonder Sleeping Beauty looked so good… She took long naps, never got old, and didn't have to do anything but snore to get her Prince Charming.
Oliver Green, Author