What Makes Someone a Light Sleeper or Heavy Sleeper?

Whether you awaken at the slightest noise or could sleep through a marching band, find out what factors impact how deeply you sleep, and how to co-sleep with the opposite.

Young couple lying in bed embracing face to face.
Getty Images

We all know someone who will sleep through anything. Garbage truck at 4 a.m.? Yep. Alarm clock blaring? Yep. They’ll sleep right on through the chaos.

On the flip side, there’s always that one person who needs absolute silence to get any shut-eye at all. A creaking step, a draft from an open window , or the flip of a light switch is enough to obliterate their hope of a good night’s sleep entirely.

In a 2019 survey, 51% of people agreed that they are a light sleeper. Approximately 55% of women and 46% of men said they fall into this sleep persona — and 50% overall said they prefer complete silence when nodding off.

With one in two people acknowledging that a slight noise can muddle their — sleep, it’s no surprise that numerous couples across the nation struggle with one partner identifying as a light sleeper and the other as a heavy, or “deep,” sleeper.

Katie Colville and Catherine Thibadeau, both 31, know the challenges of coexisting with a partner with a different sleep persona all too well. Colville, a personal trainer and elite triathlete, is the light sleeper of the pair.

“I wake up to the slightest disturbance,” said Colville. “Even our small dog jumping off the bed or a car driving by outside is enough to wake me up, and sometimes keep me up, in the middle of the night.”

For Colville — who needs to wake up early for her rigorous triathlon training before working with personal training clients all day — being a light sleeper can be understandably frustrating. Her partner, Thibadeau, on the other hand, “can sleep through thunderstorms, turbulence on airplanes, and the whining of the dogs each morning,” says Colville.

Thibadeau, a high school art teacher, says she needs sleep to be “emotionally and mentally sharp” for her students each day. Her ability to remain in dreamworld despite the noises around her is a benefit that her significant other does not always get to enjoy.

What factors make someone a light sleeper or a heavy sleeper? Why does a top-tier athlete wake up to the slightest sound waves and the high school teacher not bat an eyelid (literally)? While science does not offer one concrete answer to why certain people fall into one sleep persona or the other, there are some key factors to consider.

What science tells us about light sleepers and heavy sleepers

First, it’s important to note that there is a defined “sleep cycle” that all humans encounter each time they settle in for the night. You’ll typically move through four sleep cycles, each last ing about 90 minutes, per full night of sleep.

A sleep cycle consists of four sleep stages : three non-rapid eye movement (NREM) stages and  one rapid eye movement (REM) stage . As you move through NREM 1, NREM 2, and NREM 3 to REM sleep, the stages become progressively longer — beginning with 5 to 10 minutes for NREM 1 and extending up to 60 minutes for REM sleep. The famous “deep sleep” occurs during the NREM 3 stage .

Those who identify as light sleepers are likely spending much of their sleeping hours in REM sleep; that’s the final sleep cycle before someone awakens. In essence, light sleepers may not be entering deep sleep or staying in it long enough.

Those who are heavy sleepers, though, may spend long amounts of time in NREM stages — meaning they are gaining the benefits of deep, restful sleep.

Some studies suggest that we have “sleep spindles” in our brains, or rhythms that allow us to ignore certain noises and disruptions while we sleep. Those of us with more spindles potentially sleep more deeply than those with fewer.

Seth Davis is an adult sleep coach based in Denver, Colorado. A former insomniac, he can relate to the struggle of being a light sleeper who shares a bedroom with a partner.

“A lot of what drives our ability to get restful sleep is the mind,” said Davis. “People may have certain thoughts or stressors associated with bedtime and falling asleep that prevent them from achieving deep sleep.”

Things such as work stress, family dynamics, and current events can cause a busy brain just before bedtime, making it hard to unwind and fall asleep. Research shows that people who have difficulty falling asleep also worry more about not getting sufficient shut-eye — a negative feedback loop that only exacerbates sleep challenges.

Davis also noted that factors beyond our control, such as genetics and hormones , can play a role in our sleep personas as well.

“Science has yet to nail down one main factor that contributes to being a light or heavy sleeper,” said Davis. “Each person’s sleep needs are unique, and it’s critical we approach sleep recommendations and sleep hygiene that way.”

How to sleep better when your partner has a different sleep persona

When it comes to sharing a bedroom with a partner, though, most aren’t concerned with why they fall into the sleep persona that they do. Couples simply want to be able to cohabit in a safe, welcoming space together, especially during bedtime, according to Cassie Fallon, a licensed marriage and family therapist and Regional Clinic Director for Thriveworks.

Fallon works with families and couples on a variety of challenges — including sleep hygiene practices. “No matter the issue, whether it is sleep or something else, the biggest factor in finding a successful solution is the couple’s willingness to work toward that solution,” said Fallon. “Couples need a willingness to compromise, see their partner’s perspective, and change in order to make progress together.”

One study found that just one sleepless night can boost emotional stress by 30%. In another, couples who get less sleep tended to fight more and be generally more displeased with each other than their more well-rested counterparts. This makes complete sense — ever tried talking about something like finances with your spouse when you’re both tired? It doesn’t usually end well.

Colville and Thibadeau have seen similar frustrations bubble over due to their opposite sleep styles.

“Katie [Colville] wakes up when the dogs begin to whine to let us know they need to go out in the morning, so she bears the brunt of that responsibility,” said Thibadeau. “It can result in her getting less quality sleep for sure.”

Thibadeau also acknowledged that if she comes to bed hours after Colville has fallen asleep, pre-bedtime noises — like Thibadeau brushing her teeth or rounding up their dogs, for example — can cause Colville to wake up prematurely.     

Fallon has seen these types of sleep schedule discrepancies numerous times in couples young, old, new, and many years involved.

“A great place to start is naming the type of sleeper you are,” said Fallon. “Just acknowledging that you are a night owl, or you are an early bird, helps lay the framework for where the differences in sleep needs may be.”

Your natural tendency toward being a night owl, an early bird, or somewhere in the middle is called your chronotype. Understanding your genetically predetermined circadian rhythms can help you tweak your daytime and nighttime routines to support better sleep.

From there, Fallon suggested listing your other needs. For example, are you someone who needs a high level of communication before bed , or do you prefer to spend bedtime alone or quietly? Perhaps you need physical touch to relax. Thinking through what you need — and, of course, listening to what your partner needs — is another way to get on the same page when it comes to bedtime with your significant other.

There are also some concrete steps couples can take to compromise around their sleep needs beyond Fallon’s above suggestions.

For those who can’t seem to find their brain’s off-switch before bed, Davis offered the idea of journaling (alone or with your partner) to get all the to-dos, worries, and random rabbit holes of thoughts figuratively out of the brain. This analog activity can also be a fantastic way to find some calm connection time with your significant other (sans screens and blue light) before you hit the hay.

Want your co-journaling to be even more effective? Write down tomorrow’s to-do lists. In one study, that helped people fall asleep 37% faster than journaling about the previous day’s accomplishments.

Fallon and Davis both concurred that setting aside 30-60 minutes to be dedicated to winding down at the end of the day can help couples align their sleep schedules as well.

“There are lots of people who think they can ‘go go go’ all day and then go straight to bed,” said Davis. “For most, that just isn’t the case. We need to give our brains and bodies that time to relax and prepare for sleep.”

There are also environmental solutions, such as wearing earplugs and/or an eye mask, limiting light and noise (such as ambient TV) in the bedroom, or even getting a bigger bed to prevent contact while sleeping next to a partner.

Finding the right balance for better sleep

Colville and Thibadeau have made peace with their sleep needs and work together to find a healthy middle ground.

“Sometimes I’ll wear an eye mask to keep my exposure to Cat’s [Thibadeau’s] lights minimal,” said Colville. “Other times, Cat will compromise and come to bed at the same time as I do to minimize noise and extra movement in the room.”

While we may not know exactly what causes someone to be a light or heavy sleeper, the disgruntlement around coping with multiple sleep personas in one household is very real for many couples.

Communication, patience, compromise, and an open mind are the keys to unlocking better, more restful sleep for both the heavy and light sleepers in your life.