Our sleep continues to evolve throughout our lives, including the total hours we need and the amount of time we spend in the various stages. These changes reflect our body’s physiological changes, as well as the myriad internal and external factors that can influence both the quantity and quality of sleep. Read on for a brief overview of what to expect at different ages. For a full chart of sleep time by age, with an ideal target bedtime, read our article on the amount of sleep you need by age.
Babies:
Ask any new parent: Even though newborns are asleep a majority of the time, their sleep is woefully misaligned with adult sleep.
During the first few months of life, babies generally sleep for about 14 to 17 hours during a 24-hour period. Only about half of that is at night, though, with half taking place during daytime hours. Babies’ sleep is not yet consolidated into long stretches; instead, it’s broken up into a series of naps, punctuated by feedings, around the clock, rather than being governed by the light/dark cues that will eventually regulate sleep patterns.
The sleep that babies get is also qualitatively different, with just two stages, active and quiet sleep, which are the precursors to the REM and non-REM stages of sleep. Initially, the time spent in these two stages is about evenly split. Also noteworthy: Up until about six months, babies initially drift off directly into active sleep (the REM precursor), in contrast to the sleep patterns they’ll have as they mature, which feature active or REM sleep at the end of a cycle.
These initial sleep stages gradually morph as a result of the continued brain development taking place during the first several months of life, explains Dr. Chris Winter, a neurologist, Sleep.com advisor, and author of “The Rested Child.”
“As the brain is becoming more sophisticated, more differentiated, you start to see signals that look more like REM sleep,” Winter says. “The REM sleep is sort of an outward indicator that the important processes are happening.”
Even as the brain continues to mature, external cues (including schedules for feeding, napping, and awake time), along with regular exposure to light and dark, allow what Winter describes as the “typical markers of more mature sleep” to emerge. These include a gradual lengthening of each REM/non-REM cycle, as well as a differentiation of non-REM sleep into the three stages (N1/transitional sleep, N2/light sleep, and N3/deep sleep) seen in kids and adults. This takes place around the six-month mark, Winter says.
By about six months, babies also start to show the standard sleep progression of drifting off into non-REM sleep and then progressing to REM sleep, Winter notes. Perhaps even more important from the parent’s perspective, six months is also when babies generally start to sleep for longer stretches at night.
By about age 1, sleep has consolidated enough that toddlers are down to one to two naps during the day and a total of 11 to 14 hours of combined daily/nightly sleep.
Concerns: Issues such as breathing disturbances or acid reflux may affect babies’ sleep, Winter notes. Additionally, the American Academy of Pediatrics’ 2022 recommendations provide updated guidance on best practices to help reduce sleep-related infant deaths. These include keeping babies in the parents’ room at night in their own dedicated sleep space (not in the parents’ bed) and avoiding weighted blankets, soft bedding, and any sort of inclined sleep surface.
Young kids/Kids:
By age 3, children are down to 10 to 13 hours of nightly sleep. Between the ages of 2 and 5, most kids will cease to nap, consolidating their sleep so it all takes place at night.
At night, kids cycle through the non-REM stages (transition, light, and deep sleep) and REM sleep, just as adults do. However, they spend more time in N3 (deep sleep) than they will once they’re older. This is likely driven by the massive physical growth that takes place during childhood, Winter explains, given that deep sleep is the primary time when growth hormone is released.
Because deep sleep is the hardest to be awakened from, this also means that kids are generally not waking up during the night.
Concerns: The exception to kids’ generally deep slumber is when parasomnias — including bedwetting, nightmares, sleepwalking, and sleep talking — come into play. About half of all kids will have at least one parasomnia but typically will outgrow them by their teen years. These sleep disorders, which typically emerge during toddlerhood, take place during the N3 (deep sleep) phase.
Of these, the most common is sleep talking, which occurs in about half of all kids; it’s followed by sleepwalking, which occurs in up to 17% of kids. Sleepwalking is vastly more likely if at least one parent was a sleepwalker as a child, Winter noted in “The Rested Child.”
Breathing issues can also affect kids’ sleep, says Winter, especially during toddlerhood, when the tonsils may partially obstruct the airway.
Finally, restless leg syndrome, which is often hereditary, can also disrupt childhood sleep. In fact, “some people think growing pains are actually a sign of restless leg syndrome,” Winter points out. There’s also a broader version known as restless sleep disorder, a recently classified pediatric sleep disorder that accounts for about 8% of cases at pediatric sleep centers.
While the symptoms of a disorder such as sleepwalking or talking are often obvious, the child’s growth chart trajectory during yearly check-ups can also be a tipoff, Winter says. Because sleep issues may disrupt the release of growth hormone (which occurs primarily during sleep), this may be reflected in a sudden slowdown on the growth chart, he explains. “If they see these changes,” says Winter, “your pediatrician will start to think about things like sleep.”
Teen years:
The massive transformation kids undergo during their teen years also extends to their sleep. While teens need less sleep than when they were younger, their sleep takes on added importance, given the brain development and refinement that’s underway.
During adolescence, the focus is on pruning excess neurons and refining connectivity between the neurons and between brain regions. This takes place when they’re asleep, underscoring why teens need eight to 10 hours of nightly sleep until age 18.
Teens continue to cycle through the non-REM and REM stages throughout the night but start to show a gradual decline in the amount of time spent in N3/deep sleep, which peaks during childhood and then slowly decreases throughout adolescence and adulthood.
Perhaps most noteworthy is the dramatic change in sleep timing, as teens’ circadian rhythms, or internal body clocks, shift to a later schedule. Beginning at puberty, melatonin, the hormone that prompts feelings of sleepiness, is released later at night and also subsides later in the morning. As a result, teens aren’t sleepy until later at night (around 11 p.m.) and aren’t ready to wake.
Concerns: Unfortunately, there’s often a mismatch between the hours teens are primed to sleep and the hours they’re allowed to sleep, due largely to early school start times. When they have to wake early for school (after not going to bed until 11 p.m. or later, based on their body clocks and external demands), they wind up sleep deprived.
Nighttime sleep stealers for teens include homework demands, over scheduling, and nighttime tech use.
For girls, sleep issues including insomnia and trouble falling asleep, begin to emerge at puberty. Menstruation can also impact sleep, with physical pains like cramps and the effects of hormonal fluctuations interrupting sleep.
The bidirectional link between sleep and mental health is particularly important for this age group, given that mental health issues, including depression, anxiety, and suicidality, have continued to increase for teenagers. These issues are exacerbated by sleep deprivation and can also affect sleep.
Underlying issues resulting in excessive daytime sleepiness can also become more apparent during the teen years, Winter notes. While younger kids may have had enough free time to be able to make up for fragmented or lost sleep, teens’ schedules often don’t provide that buffer. “As kids get older, they lose the space in their days for that extra sleep,” Winter points out.
Adults:
After age 18, sleep needs remain stable until about age 65, but sleep itself continues to change. The slow decline in N3 (deep sleep) that began at the end of childhood continues, with N1 (transition) and N2 (light sleep) taking up a larger percentage of nightly sleep.
The overall time spent in REM sleep stays stable, continuing to account for about one-fourth of our total sleep time. But that’s assuming a full night’s sleep: Because more REM sleep happens during the second half of the night, waking too early cuts into REM sleep. This truncates the time spent in the stage associated with creativity, emotional processing, and additional memory consolidation and processing (building on what takes place during non-REM sleep).
Concerns: While adults should be getting seven to nine hours of nightly sleep, various lifestyle and time demands can make this difficult. Being a new parent often means fragmented sleep; job needs including shift work or frequent air travel can also disrupt sleep rhythms and total sleep time.
For those who menstruate, period-related sleep issues may continue, segueing into sleep disruptions related to pregnancy, new parenthood, and peri- and post-menopause.
Older adults:
After age 65, adults generally need seven to eight hours of sleep (rather than up to nine hours).
While the teen years brought a later shift in circadian timing, older adulthood brings the opposite, including an earlier release of melatonin. “As we mature and go through life, we generally become more circadianally advanced, waking up earlier and going to bed earlier,” Winter explains. Also, the circadian rhythm itself often weakens, Winter says, although it’s difficult to know how much is due to an intrinsic change versus external factors, such as regular exercise and regular light/dark cues, which may be disrupted in a setting such as a long-term care facility. “My guess is that there’s a diminishment in the amplitude of the circadian rhythm,” Winter says, “but I think that we also lose out on a lot of things that allow us to maintain a healthy circadian rhythm.”
Concerns: Older adults may struggle to attain enough sleep for a number of reasons. In addition to taking longer to drift off, older adults also have more fragmented sleep due to frequent nighttime awakenings. That’s due in part to spending less time in N3 (deep sleep), which is the hardest stage to be awakened from. But there are also more potential issues to prompt awakenings, Winter notes, such as a more frequent need to urinate, increased aches and pains, and side effects from various medications. As these further erode sleep, they diminish the time spent in deep sleep even further.
Sleep apnea is also a common sleep disruptor in older adults, Winter says, especially in post-menopausal women. Restless leg syndrome can also be an issue for older adults.
Sleep advice for any age
While sleep may differ by age, the core advice remains the same: Strive to get the recommended hours of sleep and address what’s disrupting your slumber, whether it’s an aspect of the sleep environment itself or an underlying issue.
Make sleep a priority: No matter how old you are, if you’re not getting the recommended hours of sleep for your age, you’re cutting into essential time that your brain and body need for everything from memory processing to physiological maintenance to emotional regulation.
Take time to wind down: Ease the transition into sleep by establishing a winddown routine, which can be helpful at any age. Babies and children thrive on consistency, but adults do too! Making a winddown routine a habit and being intentional about bedtime both help set the stage for a good night’s sleep.
Dim the lights: Bright light — including from smartphones, TVs, and computers — has an alerting effect and can delay the release of melatonin, the hormone that prompts the sensation of sleepiness. To help thwart this, turn down indoor lights in the evening and log off devices in advance of bedtime (ideally, an hour prior to your target time for lights out).
Minimize other sleep stealers: Start by following best practices for sleep hygiene and creating a sleep-friendly bedroom environment. If you’re still having issues, be on the lookout for other contributing factors. Culprits may include naps that are too long or late in the day, exercise timing, caffeine use, bedroom temperature, and noise levels.
