On average you’ll go through 3-5 REM cycles per night, with each episode getting longer as the night progresses. The final one may last roughly an hour. For healthy adults, spending 20-25% of your time asleep in the REM stage is a good goal. If you get 7-8 hours of sleep, around 90 minutes of that should be REM.

NREM sleep constitutes about 75 to 80 percent of total time spent in sleep, and REM sleep constitutes the remaining 20 to 25 percent. The average length of the first NREM-REM sleep cycle is 70 to 100 minutes. The second, and later, cycles are longer lasting—approximately 90 to 120 minutes (Carskadon and Dement, 2005).

This sequence changes somewhat between the first and second half of sleep. As sleep progresses in a series of four to five sleep cycles throughout the night, the time spent in the REM stage gets longer and the time spent in N3 sleep gets shorter, Quan said.

Waking up in the beginning stages of your sleep cycle is important because our bodies aren’t entirely shut down. Meanwhile, being awoken in the middle of REM sleep can cause grogginess that has the potential to last throughout the morning and even throughout the day.

How to improve REM sleep

1. Establish a bedtime routine. Following the same bedtime routine every night prepares the body and mind for sleep.
2. Reduce night time waking. Loud sounds, warm temperatures, and bright lights can interrupt sleep.
3. Get enough sleep.
4. Address medical conditions.
5. Avoid alcohol before bedtime.

How to Achieve More REM Sleep

1. Make exercise a daily priority. As research tells us, a single day of exercise likely won’t make a difference in REM sleep, but physical activity on a regular basis can yield improvements.
2. Plan your sleep and wake times.
3. Find creative outlets for stress.
4. Be mindful of your beverage intake.

The brain regions that generate and process emotions are 30% more active during REM sleep than during wake. This regional activation during sleep is thought to improve your mental health. Given that sleeping tablets reduce REM sleep, they may impair your ability to regulate emotion.

Some people abuse sleeping pills by taking them in excess of prescription guidelines, which increases the risk of physical dependence, addiction, and overdose. Sleeping pill addiction can also cause long-term brain damage.

A new study has linked popular sleeping pills such as Ambien and Restoril with a nearly five-fold increased risk of early death. Researchers at Scripps Health, a nonprofit health system in San Diego, estimate that in 2010, sleeping pill use may have contributed to up to 500,000 “excess deaths” in the United States.