We all know how important a good night’s sleep can be. Scientists have found that lack of sleep can play a part in increasing our risk of developing a wide range of physical and mental health problems, from diabetes to obesity, from lowered libido to heart complaints. Yet even though we are now more aware of sleep’s importance, how much do we really know about how sleep works?
Up until the 1950s, most scientists believed that when people slipped into sleep, their minds and bodies entered a form of shutdown, going into a passive condition that enabled them to recharge and recover from the exertions of the previous day. However, our knowledge of how sleep works has come a long way in the decades since. Scientists have discovered that sleep is far more complicated and at the same time more active a state than we had previously thought. In fact, sleep occurs in a predictable cycle, which is made up of two distinct parts: non-REM sleep and REM sleep (with REM standing for Rapid Eye Movement). When you go to sleep, you move through the following stages.
First stage
Minutes or even seconds after falling asleep, our brainsgenerate what scientists call alpha and theta waves. Our eye movements also begin to slow down. This first stage of sleep is relatively short and lasts usually up to seven minutes. This is the type of sleep that people who take regular short naps during the day experience. The brain is still alert to an extent and you can be woken easily.
Second stage
After the opening stage, the brain begins to produce what are known as “sleep spindles”, which are rapid increases in the frequency of brain waves. These brain waves then slow down as your brain moves towards the next phase of sleep. During stage two, your sleep is also light, and people who schedule “power naps” generally aim to wake after the second sleep stage.
Third stage
This is the point at which you enter what is known as deep sleep, when the brain generates slower delta waves and the body offers no muscle activity or eye movement. By this time, you are much harder to rouse from your sleep as your body responds less sensitively to any outside stimulus.
Fourth stage
This stage of sleep is essentially a deepening of the third stage, in which the brain produces more delta waves and you drift into an even deeper and more restorative sleep, from which it is even harder for you to be woken. This is the point in the sleep cycle when the body starts the process of repairing tissues and muscles, stimulating development, storing up energy and improving immune function.
Fifth stage
This stage is also known as REM sleep. It usually begins around an hour and a half after you first fall asleep and can continue for up to an hour. On average, adults have between five and six REM cycles each night. This is the point of the sleep cycle when the brain becomes increasingly active, stimulating dreams. Your eyes begin to move erratically during this stage, breathing becomes quicker and shallower, and your blood pressure increases. REM sleep is vital for both memory and learning as this is the time when the brain processes and stores information in your long-term memory.
Each of these sleep stages will usually last for different lengths of time according to your age. For example, an infant’s sleep cycle will be very different from that of an adult or an elderly person. However, one thing that is common to all people is that we move through the sleep cycle in a consistent sequence, with non-REM periods of sleep occurring early on, and REM periods becoming more common as the night goes by, which is why we often wake in the middle of a dream.
Our increased understanding of how sleep works has reinforced our belief in the importance of a good night’s sleep. This has also led to breakthroughs in mattress technology, and people who want to get more sleep are seeking out the latest resources – one such resource is asleep science mattress.
The more we learn about sleep, the more fascinating this state becomes, and it is clear now that each stage of our night’s sleep has a separate but important role to play in ensuring that we rest and recharge and are ready to take on the world the next morning.
