How Long Does a Sleep Phase Last?

We’re sleeping more than we have in the last twenty years, but more than one in seven people still struggle with sleep disorders. Many think the brain “shuts off” during sleep, but that’s false. In fact, the brain goes through several sleep stages and cycles while we sleep. So, what are these cycles, and what happens during them?

What are the Stages of Sleep?

Sleep involves three NREM (Non-Rapid Eye Movement) sleep stages and one REM (Rapid Eye Movement) sleep stage. This cycle lasts about 90 minutes, so we have 4-5 dream moments in one night.

NREM Stage 1

This is the first stage of sleep when you start to relax and transition from wakefulness to sleep. It usually lasts only a few minutes. Stage 1 is the lightest stage of sleep, known as light sleep, and people awakened from it don’t usually realize they are asleep.

NREM Stage 2

Stage 2 is part of NREM sleep and occurs before deep sleep. It’s harder to wake someone up; body temperature drops and heartbeat slows. This stage makes up 40-60% of total sleep time.

NREM Stage 3 (Deep Sleep)

This is the final stage of non-REM sleep, known as the deep sleep stage. It usually lasts about 30-60 minutes for adults, but for children and teenagers, it’s longer.

Brain waves slow down to delta waves in this slow-wave sleep, preparing the body for REM sleep. During this time, the immune system strengthens, tissues repair and regrow, and bones and muscles are built. Sleepwalking, talking, or night terrors can happen during this stage.

It’s much harder to wake someone from stage 3 sleep; if they do wake, they’ll feel disoriented.

REM Stage R

Phase four is known as REM (Rapid Eye Movement) sleep, the deepest stage of sleep where the most vivid dreams happen. The first REM phase usually occurs about 90 minutes after falling asleep and lasts about 10 minutes.

REM periods last between 70 and 100 minutes at night as more sleep cycles are completed.

Also, the brain becomes more active, while muscles in the arms and legs are paralyzed to prevent dreams from acting out. This stage is essential for consolidating and processing information from the previous day for long-term memory formation. As we age, we spend less time in REM sleep.

Stages Priority in the Sleep Cycle

Stages 1 and 2 are transition phases preparing the body for deeper sleep in stages 3 and 4. The initial stages are deep sleep, essential for growth, hormone regulation, and physical renewal.

During REM sleep, the brain processes memories and emotions for higher-level learning and thinking.

If someone misses out on deep sleep, their sleep quality will suffer, leading to feelings of unwellness, low mood, and potential weight gain. Their cognitive functions will slow down, and they’ll have trouble concentrating and socializing.

How to Reset Your Sleep Schedule

Research says adults need 1.6-2.25 hours of deep sleep each night or 20-25% of total sleep time.

Deep sleep is even more critical for children and infants in the growth and development stage. Babies up to 2 years old may need 4.5 hours of deep sleep. Children 2-12 years old may need slightly less, 4 hours. Teenagers and young adults need 3 hours of deep sleep to support physical and cognitive development. Addressing sleep disorders such as sleep apnea, REM sleep disorder, and narcolepsy is crucial for maintaining healthy sleep patterns across all age groups.

Why We’re So Exhausted If We’re Spending More Time in Bed: Impact on Sleep Quality

Covid-19

The Covid-19 pandemic changed how we spend our time and possibly our sleep patterns. More screen time before bed and more time alone could be causing sleep disruptions and mental health issues like stress and depression. Sleep apnea, particularly obstructive sleep apnea (OSA), may also contribute to these sleep disturbances.

Earlier, we thought the bright light from screens at night would disrupt our circadian rhythm. But newer research challenges that.

Studies led by researchers like Gradisar, who now works for Sleep Cycle, a sleep-tracking app company, have questioned the extent of this effect. For example, one study examined teenagers using iPads with varying screen brightness before bed. Surprisingly, the study found that the screen brightness didn’t affect how quickly the teenagers fell asleep.

Another study examined iPhone use in young adults and found no difference in sleep outcomes regardless of screen brightness or phone use.

Gadgets

Fitness trackers have also made us more aware of our sleep issues and created a cycle of sleeplessness. Worrying about not getting enough sleep can create a feedback loop called “orthosomnia”, where the desire to sleep becomes a source of anxiety and makes it harder to fall asleep. Additionally, the use of gadgets can exacerbate conditions like obstructive sleep apnea, further impacting sleep quality.

Gig-economy

Work is still a significant factor affecting sleep, with demands creeping into our relaxation and unwinding time. Shift work, especially night shifts or rotating schedules, can disrupt our natural sleep cycles and affect our mental and physical health in the long term. A study found that those who work non-traditional hours reported declining psychological and physical well-being over time, showing the impact of irregular work schedules on our health.