Written By: Lana Adler
Updated February 26, 2021
Your recommended amount of nightly sleep largely depends on your age. According to the latest estimates, most adults 18 or older require seven to nine hours of sleep (1) in order to feel well-rested each morning. Unfortunately, work, family obligations, and other factors often interfere with healthy sleep schedules. Not getting enough sleep can lead to daytime grogginess and even microsleep, or involuntary dozing during the day.
Establishing consistent sleep and wake times (2) is fundamental to good sleep hygiene. People who go to bed and wake up at the same times each day — even on the weekends — tend to experience more restful sleep than those who follow a less structured sleep-wake schedule.
Aligning your sleep times with natural circadian rhythms (3) is another important step toward getting an adequate amount of rest. Finding the right sleep schedule can be especially tricky for shift workers who work irregular hours or shifts, particularly those who work at night or in the early morning hours.
How Circadian Rhythms Affect Your Sleep and Wake Times
Circadian rhythms refer to natural biological processes in humans and other mammals. These internal clocks roughly follow a 24-hour cycle and correspond to exposure to light and darkness. In addition to affecting sleep patterns, circadian rhythms play a crucial role in appetite and digestion, body temperature regulation, and hormone release.
Our circadian rhythm master clock is powered by the suprachiasmatic nucleus (SCN), a cluster of cells located in the hypothalamus area of the brain (4). During the day, the retinas in our eyes detect natural light and transmit signals to the SCN. Based on these signals, the body releases cortisol, a hormone that makes you feel alert and well-rested. In the evening as light fades, the SCN triggers the release of melatonin, another hormone that helps you feel relaxed and tired before bedtime.
If you’ve ever had a difficult time falling asleep during the day or waking up in the middle of the night, it was because you were essentially fighting against circadian rhythms. On the other hand, if you've felt tired during the day when you wanted to feel alert, or alert at night when you wanted to be asleep, your circadian rhythm was probably misaligned with daylight.
In addition to circadian rhythms, another biological process known as sleep-wake homeostasis (5) can influence when and how much you sleep. Your desire for sleep — also known as your sleep drive — intensifies every hour you are awake. If you go to bed later than usual, you may sleep longer and more deeply than you might've on your normal sleep schedule.
If insufficient sleep continues over multiple days, you'll likely develop a sleep debt. Let’s say you need seven hours of sleep per night, but you only receive six. After a period of one week, you will have accrued seven hours of sleep debt (6). Sleep debt can negatively affect your cognitive functioning, as well as your overall physical health.
Best Time to Sleep and Wake Up
Going to bed and waking up in sync with natural light cycles is important for maintaining a balanced circadian rhythm, and following a consistent sleep schedule can help optimize your sleep-wake homeostasis. When choosing sleep and wake times, you should also take your sleep cycle into account.
In healthy adults, the sleep cycle includes four distinct stages. The first two stages consist of light non-rapid eye movement (NREM) sleep. As your body temperature decreases and your brain activity winds down, you enter the third stage, which is known as slow-wave sleep. This stage is also considered NREM sleep, but it is much deeper than the two preceding stages. The final stage, rapid eye movement (REM) sleep, is characterized by accelerated breathing and increases to your heart rate and blood pressure. Once REM sleep ends, your sleep cycle begins anew.
Both NREM and REM sleep are important for your overall health, but many of today’s sleep experts believe NREM sleep, particularly the slow-wave stage, is more restorative than REM. The majority of sleepers experience more NREM sleep and less REM sleep (7) during earlier parts of the night, after which REM sleep plays a more dominant role in their sleep cycle. For this reason, going to bed later can deprive you of much-needed NREM sleep and leave you feeling tired and sluggish the following day.
The best time to fall asleep and wake up may depend on whether you’re a “night owl” or more of a morning person. Also, some people don’t need the recommended seven to nine hours of sleep to properly function. That said, going to bed between the hours of 8 p.m. and 12 a.m. should provide the balance of NREM and REM sleep needed to wake up feeling alert and refreshed.
Try out different times to find the best sleeping hours for your schedule, and use your level of sleepiness to determine the most effective timetable. A bedtime calculator (8) can also help you calculate the best bedtime for you based on when you must wake up and how much sleep you want to receive.
What Is the Best Sleep Schedule for Shift Workers?
Going to bed between 8 p.m. and 12 a.m. is impossible for some people. For example, many shift workers with non-traditional job schedules are required to work evening, night, or morning hours, as well as rotating or split shifts. Shift workers made up 16% of the U.S. population (9) in 2017-18.
Sleep problems among shift employees are so common that they have their own dedicated sleep disorder. Shift work disorder (10) is characterized by two primary symptoms: difficulty falling or staying asleep during scheduled bedtimes and excessive sleepiness when working. This disorder is considered a circadian rhythm sleep disorder because many shift work schedules do not align with natural light and darkness cycles.
Obtaining enough rest can be a major obstacle for people who work non-traditional hours, but the following shift worker strategies (11) have proven effective for some:
- Keep your bedroom dark and quiet during the day, and make sure everyone in your household knows not to disturb you during your scheduled rest time.
- Invest in implements for blocking noise and light during the day, such as earplugs, a white noise machine, blackout curtains, or an eye mask.
- While at work, consume caffeine as needed near the start of your shift, but avoid caffeinated drinks and food within four hours of your scheduled bedtime.
- Take a nap during your break time if possible. Your nap should last 15-20 minutes (12) — any longer and you may enter slow-wave sleep and feel groggy when you wake up.
- Consult your doctor before taking melatonin supplements. Although this over-the-counter medication can be helpful for shift workers, it can exacerbate sleep problems if not taken in accordance with your physician’s recommendations.
- https://www.cdc.gov/sleep/about_sleep/how_much_sleep.html Accessed February 15, 2021.
- https://www.cdc.gov/sleep/about_sleep/sleep_hygiene.html Accessed February 15, 2021.
- https://www.nigms.nih.gov/education/fact-sheets/Pages/circadian-rhythms.aspx Accessed February 15, 2021.
- https://pubmed.ncbi.nlm.nih.gov/26568118/ Accessed February 19, 2021.
- https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/understanding-Sleep Accessed February 15, 2021.
- https://www.cdc.gov/niosh/emres/longhourstraining/debt.html Accessed February 15, 2021.
- https://www.ninds.nih.gov/Disorders/patient-caregiver-education/understanding-sleep Accessed February 15, 2021.
- https://www.sleepfoundation.org/bedtimecalculator Accessed February 19, 2021.
- https://www.bls.gov/news.release/flex2.nr0.htm Accessed February 15, 2021.
- http://sleepeducation.org/essentials-in-sleep/shift-work Accessed February 15, 2021.
- https://pubmed.ncbi.nlm.nih.gov/32351777/ Accessed February 15, 2021.
- https://pubmed.ncbi.nlm.nih.gov/16796222/ Accessed February 15, 2021.