If you frequently wake up throughout the night, you may not be going through all the stages of sleep, according to experts. Interrupting your sleep mid-cycle can disrupt your body and leave you feeling less rested when you wake up. Below, doctors explain the four stages of sleep and why it’s important you go through multiple sleep cycles each night.
Five or six cycles are recommended for adults, says Barbara J. Moore, M.D., F.A.A.P., associate managing editor at MCG Health, which translates to seven and a half to nine hours of uninterrupted shut-eye per night.
Meet the Experts: Hitendra Patel, M.D., medical director of the Wellstar Sleep Program and a physician with Wellstar Pulmonary and Critical Care Medicine and Barbara J. Moore, M.D., F.A.A.P., associate managing editor at MCG Health.
Hitendra Patel, M.D., medical director of the Wellstar Sleep Program and a physician with Wellstar Pulmonary and Critical Care Medicine, explains that there are some symptoms that indicate you’re not getting the restorative sleep your body needs. “Excessive daytime sleepiness despite adequate sleep duration is the main symptom,” he says. “Another sign is mood disturbance and emotional dysregulation. Fragmented sleep is linked to increased anxiety, irritability, and depressive symptoms. Sleep fragmentation has been identified as a risk factor for panic attacks and manic episodes,” he shares.
Other symptoms Patel mentions include cognitive impairment, morning fatigue, restless legs or lots of kicking during sleep, loud snoring, and morning headaches.
Here’s what experts want you to know about the stages of sleep and how to ensure a peaceful night of rest.
What’s a sleep cycle, exactly?
One sleep cycle marks the completion of all four stages of sleep, and it lasts around 90 minutes, according to Moore. But research shows that cycles can vary in time throughout the night, and over time with age.
What are the stages of sleep?
The stages of sleep are divided into two types: non-rapid eye movement (NREM), which characterizes stages one through three, and rapid eye movement (REM) sleep, which characterizes stage four. Although stages one through three are all NREM sleep, they each play important, separate roles throughout the night.
Stage 1 (NREM)
What some call the dozing off stage, the first sleep stage marks the transition from wakefulness to sleep. It typically happens over a few minutes, per the National Sleep Foundation, and it initiates a slowdown of the body’s main processes: The mind calms; heartbeat, breathing, and eye movements slow; and muscles relax.
Stage 2 (NREM)
The body moves from dozing off to a light sleep in this stage. According to the National Institute of Neurological Disorders and Stroke, eye movements stop, and body temperature drops. Most people spend more time in this stage early in the night, and the stage shortens as the cycles go on. This is when you’re most likely to be awoken by a minor noise like your partner getting into bed.
Stage 3 (NREM)
The third sleep stage marks the first deep ZZZs of a cycle—breathing and heart rate are at their lowest, and brain waves slow. Moore says this stage is “an important part of sleep and helps us to feel refreshed upon awakening,” especially because all systems are brought to a crawl, allowing for head-to-toe restoration. The bones and muscles are strengthened, the immune system is boosted, and even the metabolism can get a kick-start, Moore says. She adds that some dreaming and memory processes may also occur, although most of them take place during stage four.
Examples of sleep disorders that affect NREM sleep include sleepwalking, confusional arousals (when a sleeping person appears to be awake but acts confused or strange), and night terrors.
Stage 4 (REM)
Stage four is called rapid eye movement sleep because that’s exactly what happens. The eyes move from side to side beneath the eyelids and brain activity spikes, nearing wakefulness levels. So does breathing, heart rate, and blood pressure. Because the brain is the most active in this phase, it’s when vivid dreams occur, says Moore, but voluntary muscles (like limbs) are temporarily paralyzed so they can’t be acted out. (Thank goodness!)
“Sleep researchers think that brain metabolic byproducts and the toxins that accumulate over the day are cleared during this stage,” Moore explains. She adds that learning and memory consolidation also take place, which may explain why REM sleep has been proven to improve creativity.
REM sleep may grow longer as the night progresses, but Moore says it’s generally 25% of an entire cycle. Waking up at the end of a REM cycle is ideal, she adds, as it’s when you’re likely to feel the most refreshed.
How to get better, more restorative sleep
Lack of restorative sleep is a serious health issue, as it increases risk of several health conditions, including high blood pressure, heart attack, stroke, and depression, according to Moore. “Sleep deprivation may lead to decreased work efficiency, lapses of attention, prolonged reaction time, and trouble with memory,” she adds. Plus, those who operate heavy equipment or even drive a car to work are put in danger when they’re too sleepy to be sharp.
So, it’s time to start investing in sleep hygiene if you haven’t already. Here are Moore’s simple tips to get you started:
✔️ Stick to a bedtime: And a wakeup time, too. It will help the body establish a routine.
✔️ Set the mood: Make sure your bedroom is dark, quiet, and isn’t too hot. Do a relaxing activity and avoid large meals before bedtime. Regular exercise also helps.
✔️ Avoid alcohol: “Researchers have reported that alcohol and nicotine within four hours of bedtime may lead to sleep fragmentation and less sleep efficiency,” says Moore.
If you implement these changes and still struggle to sleep or have excessive daytime drowsiness, there may be a larger health issue at hand. In that case, Moore recommends speaking with your doctor.
Dr. Patel says that if you have any symptoms indicating obstructive sleep apnea, it’s important to be evaluated by a medical professional ASAP. The signs to watch for, according to Dr. Patel are:
- Loud, irregular snoring with witnessed breathing pauses, gasping, or choking during sleep. “Nocturnal gasping/choking is the most reliable clinical indicator of obstructive sleep apnea,” he says.
- Unrefreshing sleep regardless of duration, morning headaches, or dry mouth on awakening
- Having to urinate 2+ times per night
- Excessive daytime sleepiness, particularly involuntary dozing or drowsy driving. “This should trigger prompt referral given the increased risk of vehicular crashes,” he says.
Other symptoms, like chronic difficulty initiating or maintaining sleep multiple nights per week for at least three months, excessive movement during sleep, or a persistent inability to fall asleep at a conventional time can all indicate sleep disorders that warrant medical attention, according to Dr. Patel.
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