Health

Ask a Sleep Doctor: Is Six Hours of Sleep Enough?

Not getting enough sleep can shave years off your life, even if you never feel tired.

30-Second Takeaway

  • The CDC recommends adults get 7 to 9 hours of sleep per night.
  • Long term sleep deprivation puts you at greater risk for chronic illness, which can shorten your healthspan.

If you’re used to getting through the day with your tank three-fourths full, you’re not alone. In fact, over 35 percent of men clock in less than seven hours of sleep every night, according to CDC data. But is six hours of sleep enough? 

“The answer isn’t a simple yes or no,” says osteopathic medicine doctor Kevin Huffman, D.O. “The­re is no universal standard for slee­p. What may be enough for one person could le­ave another fee­ling tired and unenergize­d.”

Is 6 Hours of Sleep Enough?

First, know this: Most people vastly overestimate how much sleep they’re getting, according to a study in the journal Epidemiology (1). Researchers found that men who reported sleeping around six hours a night were actually getting 49 minutes less on average. So, even if you think you’re getting six hours, you might be getting closer to 5. (The best way to discern how much sleep you’re really getting is to use a device like the Oura Ring.)

That’s a problem, given that most adults need between seven to nine hours of quality sleep per night to optimize physical and emotional well-being, says Huffman. Most of us can count on a crappy morning with anything less. 

That said, there’s some wiggle room. How much sleep you need may be influence­d by factors like age, lifestyle, he­alth, and genetics, Huffman says.

Do older people need less sleep?

Nope. It’s true that people over 60 tend to sleep less on average, due to higher rates of insomnia, earlier wake times, and movement disorders like restless legs syndrome (2). But aging adults still need seven to nine hours of sleep. Anything less increases risk of age-related conditions like dementia, Alzheimer’s disease, and diabetes (34).

MORE Zs

What Happens When You Skimp on Sleep

Offsetting the negative effects of a lack of sleep with a few cups of coffee? Think again. Long-term sleep deprivation can actually axe your longevity. 

Physical health

“Insufficient sle­ep weakens your immune­ system, making you more susceptible­ to infections,” Huffman says. “And long-term slee­p deprivation is linked to a higher risk of de­veloping chronic conditions such as hypertension and diabetes.”

That’s not the end of the vicious cycle. If you already have one of these chronic conditions, sleeping less than six hours per night can take even more years off of your life, according to a 2019 study in the Journal of the American Heart Association (5). Researchers followed up with adults who completed sleep studies in the 90s. For people with high blood pressure or diabetes, sleeping less than six hours doubled their risk of death. And less than six hours of sleep tripled the risk of death for people with cardiovascular disease. 

Cognitive impairment

“When you don’t get e­nough sleep, your cognitive functions are­ impaired,” Huffman says. “[This] leads to decre­ased productivity, difficulties in decision-making, and an incre­ased risk of accidents.”

Beyond cognitive impairment, long-term sleep deprivation can increase your risk of developing cognitive diseases like dementia and Alzheimer’s. In fact, a 2017 study found that up to 15 percent of Alzheimer’s disease cases may be linked to sleep problems earlier in life (6). 

Even just one night of bad sleep may increase the beta amyloid—a protein associated with dementia—in your brain (7).  

Mental health

Nine percent of men in the U.S. struggle with depression, according to the American Psychological Association. 

Huffman notes that a lack of sleep is closely tied to depression, which can drastically shorten your healthspan. It’s a two-way street: a lack of sleep can cause depression, and depression can cause sleep deprivation. Around 40 percent of people with insomnia have depression, and around 80 percent of people with depression experience bouts of insomnia, according to the Sleep Foundation. 

Poor sleep can negatively impact your body’s biological clock and stress response, which makes you more prone to depression and anxiety (8, 9). 

SLEEP GEAR

But What if 6 Hours Feels Like Enough?

But what if you feel great with less sleep? You might have a rare condition dubbed “short sleep syndrome,” per the Sleep Foundation. 

Scientists have discovered that some natural short sleepers have a rare mutation in the ADRB1 gene, which regulates the hormones that control sleep duration and frequency (10). People with this condition can get away with six or fewer hours of sleep without increasing their risk of sleep deprivation-related health complications. 

If you’re sleeping less than six hours without an alarm, sleeping through the night, and waking up refreshed, you may have this condition.

Why You Can’t Clock More Z’s

You have a sleep disorder

If you’re regularly sleeping six hours or less, you may be dealing with an untreated sleep condition. These are the most common conditions that disrupt Zs:

Sleep apnea: a condition that causes your breathing to stop and restart throughout the night (11)

Insomnia: a condition characterized by trouble falling and/or staying asleep, even in ideal conditions (12)

Restless legs syndrome: a neurological disorder that causes unpleasant or uncomfortable sensations in your legs and an irresistible urge to move them. The symptoms are commonly  more severe at night (13)

If you think you’re dealing with a chronic sleep condition, talk to your doctor about a sleep study (more on that below).

Your bedtime routine is wonky 

If you have a busy, unpredictable schedule, it’s hard to stick to a set bedtime routine. But sleeping at different times night after night can disrupt your circadian rhythm (your internal clock) and contribute to sleep loss, according to the Sleep Foundation.

You’re stressed 

Between one- and  two-thirds of adults experience periods of insomnia (14). Psychological stress and anxiety is responsible for up to 50 percent of insomnia diagnosis, according to the National Alliance on Mental Illness. 

In severe cases, stress and insufficient sleep can turn into a hellish hamster wheel, as a lack of sleep from insomnia can heighten daytime stress.

How to Figure Out How Much Sleep You Need

The short answer: “Listen to your body. Pay attention to how you fee­l during the day,” Huffman suggests. “If you constantly feel tire­d, irritable or struggle to concentrate­, you need more­ sleep.”

Here’s other ways to figure out your sleep sweet spot:

Use a sleep calculator

A healthy sleep cycle consists of  light sleep, deep sleep, and REM sleep stages, per the Sleep Foundation. Each sleep cycle lasts 90 to 120 minutes. If you wake up in the middle of a sleep cycle, you may feel groggy and experience slower cognitive function the rest of the day. 

This sleep calculator from the Sleep Foundation uses your age and preferred sleep or wake time to suggest when to head to bed or set your alarm to avoid disrupting an incomplete sleep cycle. 

The calculator suggests two different sleep durations, which start at 6 hours and 15 minutes to account for the extra 15 most people need to fall asleep. You’ll have to experiment to see which duration works best for you.

Invest in sleep tech

Getting enough sleep is so much more involved than shutting your eyes and opening them eight hours later. You need to spend enough time in all stages of sleep—light sleep stages N1 and 2, deep sleep, and REM sleep—uninterrupted. 

Wearable sleep trackers—like the Oura Ring or Whoop—can monitor your sleeping habits to see where you’re hitting snags. 

POWER NAP

How to Get More Sleep

Stick to a set bedtime

The easiest way to improve your sleep? “A consistent sle­ep schedule,” says Huffman. A 2020 study found that people who go to bed at a consistent time each night fall asleep faster (15). 

If you’re not used to sticking to a regular sleep schedule, the Sleep Foundation notes that it may take some time to adjust. To ease into your new routine, try adjusting your bedtime by 15 to 30 minute increments each day. Eventually, your bedtime should feel like second nature. 

Avoid electronics before bed

There’s a reason you can’t settle down after scrolling for a few hours before bed. Blue light from electronics can throw off your circadian rhythm by increasing alertness (16).

Try to avoid using your phone before bed. If you absolutely must respond to that email, try blue-light glasses.

Try a sleep study

If you’ve optimized your sleep routine but still can‘t get more than six hours a night, talk to your doctor about a sleep study. You’ll spend the night at a specialized sleep facility, or wear a portable device at home, and your brain activity, eye movement, heart rate, and muscle activity are monitored (17). 

Your doctor will use the data from the sleep study to rule out any sleep conditions—like insomnia, sleep apnea, or restless legs syndrome—that could be the culprit. 

References
  1. Lauderdale, et al (2008) Sleep duration: how well do self-reports reflect objective measures? The CARDIA Sleep Study
  2. National Institute on Aging (n.d.) A Good Night’s Sleep.
  3. Sabia, et al (2021) Association of sleep duration in middle and old age with incidence of dementia
  4. Gordon, et al (2022) Prevalence of sleep-related problems and risks in a community-dwelling older adult population: a cross-sectional survey-based study
  5. Mendoza, et al (2019) Interplay of Objective Sleep Duration and Cardiovascular and Cerebrovascular Diseases on Cause‐Specific Mortality
  6. Bubu, et al (2017) Sleep, Cognitive impairment, and Alzheimer’s disease: A Systematic Review and Meta-Analysis
  7. Kojori, et al (2018) β-Amyloid accumulation in the human brain after one night of sleep deprivation
  8. Daut, et al (2018) Circadian regulation of depression: A role for serotonin
  9. Meerlo, et al (2008) Restricted and disrupted sleep: Effects on autonomic function, neuroendocrine stress systems and stress responsivity
  10. NIH (n.d.) Gene identified in people who need little sleep.
  11. NIH (n.d.) What is Sleep Apnea?
  12. NIH (n.d.) What Is Insomnia?
  13. NIH (n.d.) Restless Legs Syndrome.
  14. Bonnet, et al (2023) Risk factors, comorbidities, and consequences of insomnia in adults
  15. McMahon, et al (2020) The impact of structured sleep schedules prior to an in-laboratory study: Individual differences in sleep and circadian timing
  16. Tosini, et al (2016) Effects of blue light on the circadian system and eye physiology
  17. NIH (n.d.) SLeep Studies.