For
some people, the slightest noise awakens them at night. For others, the
wailing siren of a passing fire truck doesn’t disturb their slumber.
Just why, though, remains a bit of a mystery.
Although many people
are self-proclaimed light sleepers or heavy sleepers, researchers have
found that little is actually known about why people react differently
to noises and other stimuli during sleep.
Genetics, lifestyle
choices, and undiagnosed sleep disorders may all play a role. In
addition, some studies suggest that differences in brain wave activity
during sleep may also make someone a light or heavy sleeper.
But
whichever category you’re in, one thing is certain: The quantity and
quality of the sleep you get both play an important role in your health.
Everyone Should Cycle Through Light and Deep Sleep Each Night
During
sleep, you alternate between cycles of REM (rapid eye movement)
and NREM (non–rapid eye movement) that repeat about every 90 minutes.
NREM sleep consists of three stages, the first being the lightest stage,
during which you’re most likely to be woken up, according to the National Institutes of Health.
Stage
one, or the phase between being awake and asleep, is considered light
sleep. Deeper sleep begins in stage two, as your breathing and heart
rate become slower and your body temperature drops.
Stage three is
the deepest and most restorative stage of sleep (it’s also called
“slow-wave sleep”), in which breathing further slows, muscles relax, and
tissue growth and repair occurs.
Next is REM sleep, which is
characterized by your eyes moving rapidly from side to side, as well as
brain activity, heart rate, and blood pressure that actually look more
similar to being awake than asleep, according to the Sleep Foundation. This is the stage of sleep when the most dreaming occurs, as well as important parts of the memory consolidation process.
In general, as people age, they spend less time in the slow-wave and REM stages of sleep and more time in the lighter stages, according to a review article published in March 2018 in Sleep Medicine Clinics.
But
it’s also important to note that how much time someone spends in light
or deep sleep over the course of a night can vary significantly from
person to person and night to night. Also, the amount of deep sleep
someone gets isn’t necessarily correlated to the amount of total sleep
they get. Someone who gets eight hours of sleep a night, for instance,
may not experience as much slow-wave, deep sleep as someone else who
gets just six hours a night.
“There may be some overlap between
what people subjectively feel about the depth of their sleep and what we
find in the lab when measuring the different sleep stages,” says David Neubauer, MD,
an associate professor of psychiatry and behavioral sciences at the
Johns Hopkins University School of Medicine and associate director of
the Johns Hopkins Sleep Disorders Center in Baltimore. “But it’s not
necessarily the same thing.”
So, What Does Make Someone a Restless Sleeper?
Previous research suggests
that differences in how sleeping people respond to noise may be related
to levels of brain activity called sleep spindles. The researchers
found that people whose brains produced the most of these high-frequency
sleep spindles were more likely to sleep through loud noises. But more
research is needed to confirm the results.
If someone is not
feeling rested and thinks it’s because they are sleeping lightly, they
should look at the factors that might be contributing to their inability
to achieve a deep sleep, says Dr. Neubauer. Things like drinking
alcohol too close to bedtime or in large quantities can disrupt healthy
and consistent sleep cycles, as can keeping an inconsistent sleep schedule, according to the Sleep Foundation.
A doctor can recommend a sleep study in a sleep lab or an at-home sleep
test to see if a sleep disorder could be to blame, Neubauer says.
Some sleep disorders, such as obstructive sleep apnea, may contribute to light sleep by causing awakenings throughout the night, due to breathing irregularities.
But
it’s worth noting that just because you feel like you’re a light
sleeper or that you awaken easily during the night due to outside noise
or other disturbances doesn’t mean that you’re not actually getting the
sleep you need. What’s more important is that you wake up feeling
rested, which is a good indication that you’re getting the deep sleep
you need, says Eric Landsness, MD, PhD, an assistant professor of neurology and sleep medicine at Washington University School of Medicine in St. Louis.
Neubauer adds
that it’s hard to generalize about what makes some people light
sleepers and others heavy sleepers. “It might be some sort of genetics,
or it might be that some people have a greater degree of arousal over a
24-hour cycle,” he says.
In most cases, factors under your own
control affect the quality of sleep you get. “There are lots of issues
related to lifestyle, medications, alcohol, and caffeine that can
lighten sleep,” Neubauer says. “People might also not be getting enough
sleep because they’re not spending enough time in bed due to the choices
they make.”
How to Get More Deep Sleep Whether You’re a Light or Heavy Sleeper
If
you feel groggy during the day or find yourself falling asleep — or if
you feel irritable, experience memory problems, or have a decrease in
your attention span — you might not be getting enough sleep, or more
specifically, enough quality sleep. To get to the root of the problem,
try these remedies to help reset your sleep schedule, or talk to your
doctor or consult a sleep expert if these tactics are still not helping.
To improve the quality of your sleep, the following may help:
- Have a set bedtime and a set wake time. Also, try to avoid staying up late and sleeping in on weekends, says Rajkumar Dasgupta, MD,
assistant professor of clinical medicine at the University of Southern
California’s Keck School of Medicine in Los Angeles and a spokesperson
for the American Academy of Sleep Medicine. Staying up on weekends makes
it difficult to go to sleep early on Sunday night, which then leads to
fatigue the next day.
- Manage stress all day long. Higher levels of stress are associated with sleeping less, according to the American Psychological Association.
And research suggests that there may be an underlying biological
explanation as to why stress is more likely to disturb some people’s
sleep, according to a review published in December 2018 in the Journal of Sleep Research.
- Avoid alcohol close to bedtime. It
may do a good job of knocking you out in the short term, but it
interferes with deep sleep, says Dr. Dasgupta. That’s because drinking
before bedtime may cause disruptions to your sleep cycle as your liver
enzymes metabolize alcohol, according to the Sleep Foundation.
- Turn off the TV and keep electronic devices away from the bedroom. “Keep your cell phone out of the room, so a text won’t wake you up, especially if you’re a light sleeper,” Dr. Landsness says.
- Avoid screen time at least 30 minutes before bedtime. Unplugging an hour or more before your head hits the pillow is even better. The light from screens messes with sleep by discouraging the body from releasing melatonin,
which is the hormone that signals to the body that it’s time to fall
asleep. And engaging with tech devices, even if just to answer a couple
of emails or watch a TV show, is more energizing than relaxing, and it
leads to cognitive arousal.
- Wear an eye mask.
This will block light that may be seeping into the room from the edges
of your curtains. “Light sleepers are prone to light contamination. That
tiny bit of light emanating from the streetlight outside could affect
your sleep,” Landsness says. Studies
suggest that wearing an eye mask can help people sustain longer periods
of REM sleep, and that it encourages elevated levels of melatonin.
- Use earplugs or noise-canceling earbuds.
This will help drown out ambient noise, especially if your bedroom is
facing a window that picks up traffic sounds from outside, Landsness
says. You can also try a fan or a white-noise machine that can play
soothing sounds to help you fall asleep. A study published in December 2017 in Frontiers in Neurology found that the gentle hum of these kinds of devices can help some people fall asleep faster.
- Watch what you eat close to bedtime. Try to avoid snacks packed with sugar, which could cause a sugar spike. Also avoid caffeine and nicotine, both of which are stimulants. And spicy, acidic foods may cause heartburn or acid reflux that can interfere with sleep, according to the Sleep Foundation.
Additional reporting by Katherine Lee and Carmen Chai.
