The Science of Sleep: How Understanding Your Sleep Cycle Can Help You Prevent Sleep Apnoea and Snoring

Even though sleep has been extensively studied, why we need to sleep and what happens to the body if we don’t get enough sleep isn’t fully understood. What we do know is that sleep is incredibly complex, affecting all parts of the body. The brain is heavily involved in producing chemicals and hormones that regulate sleep and wakefulness. Although there is still a lot we don’t know about the process of sleep, knowing how it is connected to physical, emotional and mental health can provide useful insight into how to gain better sleep.

Immediately after you fall asleep, some notable changes affect your body and brain, including a drop in temperature, heart rate and respiration, and brain activity. While you sleep, your energy expenditure is, unsurprisingly, lower. During the night, you progress through various sleep cycles, each lasting between one and two hours. There are four distinct stages of sleep that fall into two different categories. The first three stages of sleep are non-REM sleep. The fourth stage is REM or rapid eye movement sleep.

During stage one, you have just fallen asleep and begin transitioning into stage II after five minutes or so. At this point, your brain activity starts to slow further. It is very easy for you to be awoken during these early stages of the sleep cycle. The third stage of sleep is the deepest point of sleep. Your muscles and body become more relaxed, and your brainwaves are distinctly different from waking brain activity. This stage of sleep is thought to be very important for allowing the body to regenerate, recover, and consolidate memories.

Stage IV sleep is when brain activity picks up significantly during REM or rapid eye movement sleep. At this point, most of the body is temporarily paralysed apart from the muscles involved in breathing and your eyes. Most intense dreams take place during REM sleep. REM sleep is thought to be very important for memory and learning, and most of this stage of sleep occurs during the second half of the night. These sleep cycles are known as sleep architecture, and each stage significantly affects healthy sleep quality.

Your body regulates sleep with something called sleep-wake homeostasis. It is a sensation we are all familiar with, where when we have been awake for a long time, we begin to feel the need to sleep. Sleep is also regulated by the circadian rhythm, which lasts 24 hours and has an important role in biological processes, including sleep. The circadian rhythm is largely influenced by light exposure, helping us feel more wakeful during the day and sleepy during the nighttime.

Numerous hormones and chemicals are involved in sleep-wake homeostasis and the circadian rhythm. Hormones are particularly important, including melatonin, which promotes healthy sleep quality and is produced naturally as exposure to light decreases. The function of these hormones and chemicals can differ in individuals, which is thought to be due to genetics, which is why some sleep disorders, including sleep apnoea, can run in families.