Long gone are my college days when pulling all-nighters was no big deal and functioning on a few hours of sleep was like a badge of honor. If I don’t clock in at least a solid seven hours nowadays, I feel it the next day: brain fog, impaired memory, moodiness (I could go on). The reality is not getting adequate sleep can be a detriment to your health, even if you eat well and exercise regularly.
We’ve been told time and time again that the golden rule of sleep is getting eight hours each night. After all, sleep plays a crucial role in basically every function of the body, from your cognitive function to mental and physical performance to immunity. But is eight hours of sleep really the magic number to optimal health, and what actually happens to your body when you play by the rules and get enough sleep? I asked sleep experts to break it down.
Dr. Audrey Wells, Sleep Medicine Advisor for CPAP.com and Founder of Super Sleep MD
Dr. Audrey Wells, MD, is the Sleep Medicine Advisor for CPAP.com and also a leading figure in the world of sleep and obesity medicine. As a board-certified physician in both specialties, and her expertise in CPAP therapy, cognitive behavioral therapy for insomnia (CBT-I), and life coaching, Dr. Wells provides comprehensive solutions to help people feel their best.
What happens to your body when you get eight hours of sleep a night?
You support your immune system
Jacob Smith, a board-certified sleep therapist, explained that sufficient sleep can enhance immune function and reduce the risk of getting sick. When you sleep, your immune system releases proteins called cytokines that help control inflammation in your body and allow your immune system to go into defense mode if germs or other substances that can make you sick enter your body. Getting enough sleep means producing these protective cytokines as well as infection-fighting antibodies and cells.
You boost your energy levels
We can all attest to waking up on the right side of the bed after a solid night of sleep—you feel energized and ready to take on the day. One study found that sleep restores energy and allows the storage of energy to be used throughout the day, whereas lack of sleep hinders access to and normal use of energy stores. Another study revealed that a person having slept six hours instead of eight would have to apply 25 percent more energy to function.
You improve your cognitive function and emotional well-being
While you sleep, the brain releases waste products and toxins that accumulate throughout the day, which leads to better brain functions that process daily events and regulate emotions and behaviors. In other words, from memory and learning to reducing anxiety by rethinking a challenging situation, sleep impacts our everyday functions. A healthy amount of sleep is also vital for “brain plasticity,” or the brain’s ability to process what we’ve learned during the day and remember it in the future.
You more easily manage your weight
Getting fewer than six to seven hours of sleep has been continually linked to a higher body mass index (BMI) and weight gain. Because sleep regulates metabolism—the process in which the body converts food to energy—continuing to get a good night’s sleep may help you avoid decreases in metabolism that can happen when you haven’t gotten enough sleep. What’s more, quality sleep aids in keeping levels of ghrelin (the appetite-stimulating hormone) and leptin (the satiety-inducing hormone) balanced, so you’re able to tune into your hunger cues.
You enhance your skin health
It turns out beauty sleep is real. During sleep, your skin’s blood flow increases, causing it to rebuild its collagen and repair damage from UV exposure. The result? Fewer wrinkles and age spots. Additionally, as you sleep, your skin undergoes rapid cell turnover, where dead surface cells are shed to make way for newer ones. It also builds elastin and hyaluronic acid, resulting in a more hydrated, plump, and even-toned complexion.
Do you actually need eight hours of sleep?
I think it’s fair to say we all strive for sound, uninterrupted Zzzs and waking up bright-eyed and bushy-tailed in the morning, but is the prescribed eight hours of sleep really necessary? While the National Sleep Foundation recommends seven to nine hours of sleep for adults, the key to restful sleep isn’t one-size-fits-all. According to Smith, some individuals may naturally require less sleep and still function optimally, while others may need more sleep to feel their best. Many factors, including age, genetics, overall health, lifestyle, and activity levels, can influence an individual’s sleep needs.
You may need more sleep after more vigorous workouts, thanks to muscle fatigue lowering your energy levels. According to Dr. Audrey Wells, sleep medicine advisor at CPAP.com and founder of Super Sleep MD, if you have a history of chronic sleep debt (AKA the difference between the amount of sleep our bodies need and the amount we actually get), one full night of sleep is not going to be sufficient to repay that debt. According to a 2016 study, it takes approximately four days to recover from one hour of lost sleep.
Why do you still feel tired after sleeping eight hours?
So you’ve achieved eight hours of rest, but you’re still not feeling restored. What gives? Here are four reasons why you could be waking up tired after a full night of sleep.
You may not be getting quality sleep
You could be in bed for eight hours but be tossing and turning all night and never fully hit your deep sleep phase, leaving you feeling anything but well-rested. “While sleep quantity is a common metric for assessing sleep, the importance of sleep quality and consistent sleep timing should also be emphasized,” Dr. Wells conveyed. “Persistent tiredness despite getting eight hours of shut-eye should prompt evaluation for poor sleep quality or irregular sleep timing.”
How do you know if you’ve gotten ample quality rest? Smith advised considering your daytime alertness and productivity. Check in with how you feel in the morning and during the day. Do you wake up feeling refreshed and consistently feel alert, focused, and energized throughout the day? Can you perform daily tasks efficiently, maintain concentration, and have good cognitive abilities? If so, you’re likely obtaining your own personal sleep requirement. If you answer “no” to those questions, you could be experiencing sleep disruptions and should address your sleep practices and lifestyle (more to come on that). It could indicate an underlying sleep disorder.
You may have a sleep disorder
There are over 80 sleep disorders that impact the quality, timing, and duration of your sleep. And sleep troubles are so common that the CDC declared sleep disorders a public health epidemic. If you’ve been struggling to fall or stay asleep, you could have insomnia. Other sleep disorders like sleep apnea (when your breathing stops and starts while you’re asleep) or restless leg syndrome (which causes a very strong urge to move the legs) can disrupt the rest your body needs in order to maintain wakefulness.
While it’s normal to experience bouts of sleeplessness here and there, consult a doctor if you have trouble sleeping for more than three months. That could look like:
- taking longer than 20 minutes to fall asleep
- consistently waking up for 30 or more minutes throughout the night
- feeling exhausted even after seven to eight hours of sleep
You may have stress and anxiety
When your mind keeps racing with a laundry list of “what-ifs” and to-dos or you keep replaying that one embarrassing moment as you lay in bed, chances are counting sheep doesn’t stand a chance. Excess worry and fear make it harder to fall and stay asleep through the night, creating a sleep debt. This can worsen anxiety, creating a negative cycle that may lead to insomnia.
You may lack proper sleep habits
To get the best sleep of your life, the expert-backed pillars of quality sleep apply:
- Follow a consistent sleep schedule
- Limit your screen time before bed
- Set a food and alcohol curfew
If you go to bed and wake up at different times every day, it throws off your circadian rhythm and your body is likely confused when it’s supposed to be asleep versus awake, so aim to fall asleep and wake up within the same hour every day. Guilty of bringing your phone to bed or binging your latest Netflix obsession at night? Well, a study revealed that light exposure from screens can suppress sleep hormones and disrupt the circadian rhythm, making it difficult to fall asleep. Instead of scrolling or watching TV, get lost in a book or listen to soft music to relax. Finally, cutting off caffeine at lunchtime and curbing your intake of food and alcohol three to four hours before bed is key to a good night’s rest. That’s right: Bidding adieu to your afternoon pick-me-up and favorite nightcap is the sacrifice we have to make for a good snooze.
