The latest research on the importance of sleep cycles, the roles they play and just how much sleep you really need
What’s your sleep sweet spot? It turns out you might have a few choices, according to research examining the quality and quantity of our sleep cycles throughout the night. Both need to go hand in hand for optimal health. The thinking now is that getting deep, restorative snooze time should be our top priority. It’s worth looking at a bit deeper.
How much sleep do you really need?
The consensus about the appropriate amount of sleep has remained steady for a while now. Experts think somewhere between 6 to 8 hours is about right for most adults. A study in the journal, Brain, said that adequate sleep each night can delay cognitive decline and keep our brains in tip-top shape.
Researchers are quick to point out that the amount of sleep you need is highly personal, influenced by gender, age and genetics.
The latest science demonstrates that sleeping less than 5 ½ hours is problematic though. Studies have shown that insufficient sleep contributes to poorer cognitive performance. One study published in JAMA Neurology found that older people who slept fewer than 6 hours had more beta-amyloid in their brains, a hallmark sign of Alzheimer’s disease. It may surprise some people to learn sleeping in excess of 7 ½ hours can also cause issues with cognitive performance.
But don’t get too hung up on the number of hours. It matters but it’s not the only consideration for good sleep. Find your own sweet spot where you sleep well enough to wake up refreshed and feeling good. The aim should be to sleep through multiple cycles – each one lasts around 90 minutes – without waking.
So let’s talk about sleep cycles
Understanding sleep cycles is important. As sleep medicine expert Dr. Funke Afolabi-Brown explains, sleep is divided into two distinct phases. non-rapid eye movement (NREM) and rapid eye movement (REM) sleep. “We spend about 75% of our sleep time in NREM sleep, which is further divided into 3 stages corresponding to light, medium and deep sleep – Stages N1, N2, N3,” she says. “The rest of our sleep time is spent in REM sleep. A full sleep cycle comprises of these stages with NREM sleep occurring more at the beginning of the night. REM sleep is more prominent at the latter part of the night.”
What do these sleep cycles do and when do they happen?
NREM sleep, particularly Stage 3 sleep is when we experience our deepest and most restorative sleep, notes Dr. Afolabi-Brown. In Stage N1, we drift from wakefulness to sleep and become less aware of our surroundings. Our eyes start to close and roll back into our heads. It’s a drowsy state and occupies about 5% of our sleep.
Stage N2 takes up almost 50% of our total sleep time. Our brains develop a unique pattern called sleep spindles. As we prepare to enter into the deep stage of sleep, our brain waves become slower. This stage is thought to be responsible for forming and cataloguing memories.
Stage N3 is also known as deep sleep or slow-wave sleep and occupies the majority of the first 3rd of the night. During this stage, our bodies undergo repair, restoration, tissue growth and strengthening of our immune system. This is felt to be the most refreshing – and healing – sleep stage. Heart rate and breathing slow down and become very regular. During this stage, our bodies produce hormones, consolidate memories and form new ones. Learning new skills also happens. If you are suddenly awakened out of this stage, you may feel groggy, a term known as ‘sleep inertia.’
REM sleep may be something you’ve heard about before. Known as ‘dream sleep,’ it’s predominant in the last third of the night, she says. Most of our muscles stop moving, but our eye muscles continue to actively move. Our brains are also quite active during this stage and our heart rate and respiratory rate may increase. “REM sleep is felt to play an important role in learning and memory,” she adds. “Newborns and infants spend up to 50% of their total sleep time in REM sleep, highlighting the importance of this stage in development.”
Finding your own sleep sweet spot
Most of us aren’t able to undergo a detailed clinical sleep analysis to figure out our personal sleep cycles and need for sleep. But there are steps you can take to better understand your personal sleep style. Dr. Chelsie Rohrscheib, head sleep specialist and neuroscientist with Wesper (a sleep technology company), suggests keeping a sleep diary for two weeks. “Track the hours and minutes of sleep you needed to feel refreshed the next day and aim for that sleep time going forward,” she recommends. “The amount of sleep you need is highly dependent on genetics and how efficiently your brain and body can accomplish all of the biological processes that occur.”
It’s clear there’s a lot of crucial repair and rejuvenation going on in our bodies while we snooze. That makes inadequate sleep an impairment to health. “Poor sleep inhibits all the processes mentioned above,” explains Dr. Rohrscheib. “After chronically under-sleeping or chronic sleep deprivation, your body will become weak. Your cognitive functions will become dysfunctional, and your risk for chronic diseases and infections will increase.” You’ll also be at higher risk for several mental health disorders including depression and anxiety. Finally, because your body becomes so dysfunctional when you’re sleep deprived you’ll be more likely to gain weight.
Try to get sleep during the “golden hour” – the window between 10 pm and 11 pm. In their December 2021 study, UK researchers tracked the diagnoses of cardiovascular disease for almost 6 years.
It found cardiovascular events were lowest among those who fell asleep between 10 pm and 10:59 pm, while the risk was 12% greater for those who went to sleep between 11 and 11:59 pm and 25% higher risk among people who fell asleep at midnight or later. The data shows that the golden hour is a true sweet spot for heart health. Going to bed earlier than 10 pm also showed an increase (24%) in cardiovascular events. Aim for that sweet spot for better health.
Rest well & wake up ready to go!
Better sleep gives rise to better mornings, bringing your goals into focus and dreams within reach. Hungry for more sleep info? Dig into these posts:
- Time for a night divorce?
- 17 hacks to get you through a sleep-deprived day
- Sleep problems caused by allergies are nothing to sneeze at