Sleep plays a complex and fascinating role in the way our bodies and brains function, rest, and recover. When it comes to sleep, patterns and preferences can vary significantly from person to person.

While many people favour monophasic sleep (which involves sleeping once per day, usually overnight), others may prefer a biphasic sleep pattern. Biphasic sleepers sleep twice a day, often with one longer period of sleep and one short nap. A 2020 study conducted in Oman found that 46% of participants had a biphasic sleep pattern, while 26% were monophasic sleepers. 28% adopted the practice of having several short sleep episodes across a 24-hour period, which is known as polyphasic sleep.

The study of sleep is still relatively new, with key milestones such as the discovery of rapid eye movement (REM) sleep taking place as recently as 1953. However, past and recent research in the field of sleep has uncovered interesting information about why we sleep, how we sleep, and what effects sleep can have on our overall well-being.

1. Humans spend a third of their life sleeping

Research published in the Handbook of Clinical Neurology suggests we spend one-third of our lives sleeping or attempting to do so. Considering how many important processes happen within the brain and body while we’re asleep — such as the regulation and repair of the immune system — it’s perhaps unsurprising that we spend a considerable amount of our lives at rest.

2. The time it takes to fall asleep can be an indicator of sleep health

Research from 2018 shows that people who believe they fall asleep within 10 to 15 minutes of their head touching the pillow are more likely to have good overall sleep health. If it takes a person longer than 15 minutes to drift off, sleep health may be suffering — after more than 30 minutes, sleep efficiency is reduced. On the other hand, falling asleep immediately can be an indicator of sleep debt.

3. Lunar phases may affect sleep patterns

A 2013 study examining the potential effects of lunar phases on sleep found that near a full moon, electroencephalogram (EEG) delta activity during non-REM sleep — an indicator of deep sleep — decreased by 30%. Additionally, the time taken to fall asleep increased by 5 minutes and total sleep duration decreased by 20 minutes. Humans are not the only beings whose biological processes may be influenced by the moon: it is believed that hormonal changes and reproductive cycles in animals are also affected by lunar phases.

4. Genetics can influence how much sleep you need

Genetics have a significant influence on both normal sleep and certain types of sleep disturbances. In a study published in 2019, researchers identified a rare mutation in the ADRB1 gene that was being passed through families with people who had naturally short sleep patterns. This gene codes for one of our adrenergic receptors, which are found on many cells in the body and react to hormones — including those that are responsible for managing sleep patterns.

5. Human sleep patterns have changed considerably over time

In Medieval times, most people were biphasic sleepers — meaning they slept for two periods each night with a spell of wakefulness in between. This waking time was known as “the watch,” and it was used for a variety of tasks. A person might have tended to their fire, completed household chores, carried out prayers, or socialized with their family during the watch. By the end of the 20th century, monophasic sleep had become prevalent in many populations. This shift is believed to have been caused by changing work habits and the widespread presence of artificial light, which allows people to stay awake further into the night and can interfere with sleep patterns.

6. Pain tolerance is reduced by sleep deprivation

A growing body of research indicates that sensitivity to pain increases when a person is sleep-deprived, and their pain threshold falls. Findings from a 2019 study show that even modest changes in sleep quality each night can determine consequential day-to-day changes in experienced pain.

7. Sleeping on your left side can aid digestion

The small intestine moves waste to the body’s right side, where it travels to the large intestine and then to the lower colon on the left side. Thanks to the pull of gravity, sleeping on your left side may aid digestion — research suggests that this sleeping position may be particularly beneficial to those with gastroesophageal reflux disease (GERD).

8. Insomnia is the most prevalent sleep disorder in Canada

A considerable proportion of Canada’s population is affected by insomnia on a short-term, recurring, or chronic basis. Characterized by difficulty sleeping, poor sleep, and subsequent impairment of daytime function, insomnia is a sleep disorder that can lead to negative health consequences over time if left unmanaged. It’s important to consult your doctor if prolonged periods of insomnia are interfering with your day-to-day life.

9. Sleep deprivation can increase feelings of hunger

The body’s levels of ghrelin (known as the “hunger hormone”) and leptin, a hormone that regulates appetite, are impacted by sleep deprivation. Research shows that ghrelin levels can rise when a person is sleep-deprived, while leptin levels may fall, leading to increases in subjective hunger.

10. “Counting sheep” may not be an effective way to induce sleep

Counting sheep as a way to promote sleep is a practice thought to have its origins in a process carried out by shepherds in Medieval times. In order to use communal grazing lands, shepherds were required to take a headcount of their sheep every night before they went to sleep. However, a study that asked participants to visualize certain images as they were trying to drift off found that those who “counted sheep” actually stayed awake for longer than they normally would.

Our understanding and knowledge of sleep is still developing: but what we do know tells us that sleep is a fascinating and complicated part of the human experience that we still have much to learn about.