Lighter sleep with age: how can you adjust your sleep?

With age, deep sleep decreases and waking during the night becomes more frequent, which is a common age-related change; sleep need itself does not fall. What you can adjust are daily habits: wake at the same time every day, get morning light, put your phone away before bed, time caffeine and alcohol, and keep the bedroom cool, dark and quiet.

How does a night of sleep work?

Sleep is not equally deep all night; it runs in repeated cycles of roughly 90 minutes.

Cycles of roughly 90 minutes

Each cycle alternates between non-REM and REM sleep. The US National Heart, Lung, and Blood Institute (NHLBI) describes a cycle as lasting about 80 to 100 minutes, with four to six cycles in a typical night. You may wake briefly between cycles without noticing.

Deep sleep (slow-wave sleep)

The deepest non-REM stage is called slow-wave sleep, after the slow pattern of brain waves. It is concentrated in the first half of the night. If the first half of the night is often disturbed, you get less deep sleep.

REM sleep

REM sleep becomes more common toward morning. Brain activity in this stage is close to waking levels, and dreaming usually happens here. Waking earlier than usual or broken sleep in the early hours may shorten REM sleep.

How much sleep is enough?

The consensus of the American Academy of Sleep Medicine and the Sleep Research Society (Watson et al. 2015) states that adults should regularly sleep at least 7 hours a night. The US National Institute on Aging (NIA) states that older adults need about the same amount of sleep as all adults, around 7 to 9 hours.

How does sleep change with age?

With age, sleep tends to become shorter, lighter and more often interrupted during the night. This is a common change seen in many people. Sleep need does not fall with age; what changes is the pattern of sleep.

Less deep sleep

The NHLBI explains that deep sleep decreases with age. The feeling of "not sleeping as deeply as before" in your 40s and beyond fits this age-related change.

More night-time waking

The NIA notes that as people age, the time spent in each type of sleep decreases, sleep becomes shorter and lighter, and waking during the night may become more frequent. When sleep is lighter, noise, light or a trip to the bathroom wakes you more easily than when you were younger.

An earlier body clock

Older adults often feel sleepy earlier in the evening and wake earlier than they did when younger. The NHLBI explains that the rhythm of the body clock changes with age, and that less physical activity or less time spent outdoors also affects it. If you keep the same bedtime while your body wakes earlier, your sleep becomes shorter without you noticing.

What you can adjust day to day

• Wake at the same time every day and get daylight in the morning, for example by opening the curtains, walking outdoors or eating breakfast near a window
• Move and go outdoors during the day, since the NHLBI notes that less physical activity and less time outdoors affect the rhythm of the body clock
• Avoid large amounts of liquid late at night to reduce trips to the bathroom during the night
• Time caffeine and alcohol, and set up the bedroom as described below

Why does using a phone before bed make it harder to fall asleep?

A phone before bed affects sleep in three ways: the light from the screen, content that keeps you alert, and time that slips away unnoticed.

Light from the screen

The body clock uses light and darkness as timing signals. In the evening the body releases melatonin, the hormone that tells the body it is night-time, which is released when it gets dark. The NHLBI states that bright artificial light late in the evening, such as from a TV or smartphone, can disrupt the release of this hormone and make it harder to fall asleep.

Content that keeps the brain alert

News, work messages, short videos and games keep the brain in an alert, responsive mode, the opposite of winding down before sleep. Alerts during the night can also wake you during stages when sleep is already light.

Time that slips away

Scrolling has no clear end point, so "just a bit more" easily becomes half an hour. With the same wake time, a later bedtime cuts directly into your hours of sleep.

Putting the phone away before bed

• Put your phone and other screens away for a while before bed, and use that time to relax, for example by reading, listening to quiet music or taking a warm bath
• Turn off notifications, or schedule do-not-disturb mode
• Charge the phone outside the bedroom; the NIA says to avoid watching TV or using a computer, phone or tablet in the bedroom
• If you use your phone as an alarm, switch to a simple alarm clock that is not brightly lit

Does catching up on sleep at weekends help?

Sleeping in much later than usual at weekends makes your wake time irregular. The body clock uses morning light as a timing signal, so when you wake and get light several hours later, the next workday morning can be harder.

The NIA says to go to bed and get up at the same time every day, including weekends, and the Watson et al. 2015 consensus states that adults should regularly sleep at least 7 hours a night. The basic approach is therefore to get enough sleep on work nights and keep your weekend wake time close to your workday one, rather than catching up all at once at the weekend.

After a night shift, how can you reset your body clock?

The NHLBI explains that the body clock is set by light and darkness, and night shift work can put your sleep time out of step with this rhythm. When you have to sleep during the day, what you can adjust is your environment and timing.

• Make the bedroom dark with blackout curtains, and reduce noise with earplugs or steady background sound
• Reduce bright light and screens before going to bed, as you would before sleeping at night
• Keep your sleep period as consistent as you can, even on days off shift
• Count caffeine timing from your own bedtime, not the clock, and avoid heavy meals close to bedtime

How do caffeine and alcohol affect sleep?

Caffeine

Caffeine stays in the body for several hours, so avoid it late in the day. Caffeine is not only in coffee but also in tea, chocolate and soft drinks. Even if you stop coffee after lunch, iced tea or soft drinks in the evening still contain caffeine.

Alcohol

Alcohol may make you drowsy and fall asleep faster, but it makes the second half of the night more fragmented and lighter, and it may shorten REM sleep. The NIA says to avoid alcohol, even small amounts, for good sleep.

Heavy meals and drinks before bed

The NIA says to avoid large meals within two to three hours of bedtime and large amounts of liquid late in the day. A heavy meal close to bedtime means the body is still digesting while you try to sleep, and drinking a lot before bed raises the chance of waking to use the bathroom.

How should you set up your bedroom, exercise and naps?

A cool, dark and quiet bedroom

Core body temperature tends to fall slightly as sleep begins, so a comfortably cool room suits the start of sleep. Blackout curtains block outside light, and earplugs or steady background sound reduce noises that wake you during lighter sleep.

Time exercise and naps

Regular exercise is part of good sleep habits, but the NIA says not to exercise within three hours of bedtime and to avoid naps in the late afternoon or evening, since they reduce the sleepiness that builds up for the night.

These are everyday factors you can adjust.

When should you see a doctor?

If you have ongoing concerns about your sleep, talk to a doctor.