It’s easy for us to think that when we sleep, our brains become inactive and rest to recover from the day’s activity. But guess what? Our brains don’t actually turn off at night. They’re more active when we’re asleep than when we’re awake. This is because our brain goes through distinct patterns of activity when we’re getting our shuteye, which are characterized as different stages in our sleep cycle.
We don’t have just one sleep cycle per night, either. A typical person will begin a sleep cycle every 90-120 minutes when they are asleep, which results in about 4-5 sleep cycles per night.
We begin with non-REM sleep and ultimately progress into Rapid Eye Movement (REM) sleep, which is when we dream. We spend about 2 hours each night dreaming, but we don’t always remember most of our dreams.
Get to know your five stages of sleep:
Stage 1 – Drifting Off
We experience Stage 1 sleep soon after we begin to nod off. Our brain is slightly relaxed, usually operating under Alpha and Theta waves (you can learn more about your brain waves here). During this stage, our eye movements begin to slow down, we start to feel drowsy, yet we are still able to hear things and have some sense of feeling awake. Stage 1 is brief — typically lasting around 7 minutes.
Stage 2 – Light Sleep
Taking up a majority of our sleep cycle (about 45% of the cycle), Stage 2 is classified as ‘light sleep.’ This is when our brain waves slow down and we are asleep, but can be easily awoken. During Stage 2, our body temperature decreases, our heart rates slow, our brains processes memories and emotions, and our metabolism regulates itself. We experience ‘sleep spindles’ during this phase, which are occasional bursts of rapid, rhythmic brain waves.
Stage 3 – Deep Sleep
In Stage 3, we are in a deep sleep that transitions us between light sleep and our deepest sleep.
Stage 4 – Very Deep Sleep
Also known as Delta sleep, this is our deep sleep phase and is the most difficult to wake up from. Our breathing is slowed and our muscles are relaxed. For people who sleep walk or sleep talk, this is the stage in which both are most likely to occur. The thinking parts of the brain are largely offline and we are not dreaming. During Stage 4, we experience cellular maintenance, as sleep allows the brain to rest, repair, and grow new cells. At this time, the brain removes toxins that are built up throughout the day to allow itself to function normally the next day.
In REM, our brain is very active while our body is largely inactive. Our eyes are moving rapidly and our bodies are largely paralyzed. This is the stage in which most dreaming happens, and we experience increased respiration.
Napping and your sleep cycle
If you’re a fan of an afternoon nap, make sure to keep them short. When we nap between 30-60 minutes, we hit the deep stages of sleep which makes us feel groggy when we wake up. It also can hinder us from falling asleep that night if we’ve already had restorative sleep during the day. Best practice? Keep it about 20 minutes. Or, if you have enough time to sleep for 90 minutes, you can go through all of your sleep cycle and wake refreshed.
Making the most of your sleep
Ensuring that we get enough sleep to properly go through each of the sleep stages is critical to living a healthy lifestyle. When we don’t get enough sleep, we don’t spend enough time going through each stage adequately. When we’re sleep deprived, our body spends more time in Stage 4, deep sleep. To make the most of our sleep, keep your bedroom at a comfortable temperature, block out surrounding light and noise, stick to a regular sleep schedule, and avoid caffeine 4-6 hours before bedtime.