There are tons of sleep hacks, supplements, and cozy pajamas that can improve your sleep, but that doesn’t mean falling and staying asleep is easy. That’s why some people, when they feel completely comfortable with just a few hours of sleep, assume that it’s good enough – but that’s not entirely the case.
Simply put, sleep is the maintenance system that keeps every organ functioning properly, says Andrea Matsumura. “The seven to nine hour recommendation is based on decades of research and shows that adults who consistently sleep in this range have better long-term health outcomes, including lower rates of metabolic disease, cardiovascular disease, cognitive decline and mood disorders,” she says.
Meet the experts: Andrea Matsumura, MD, is a specialist in internal medicine and sleep medicine. Angela Holliday-Bell, MD, is a board-certified physician and certified sleep specialist. Morgan Soffler, MD, is a board-certified sleep physician and assistant professor of medicine at New York Medical College.
But what if you sleep less than seven hours a night and don’t feel tired? Ahead, find out why this might be a bit problematic — and how experts say you can get your sleep back on track.
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Why you feel good even though you haven’t slept much
Personal sleep needs are influenced by genetics, age, circadian rhythms, illnesses, environment, lifestyle and hormonal changes such as puberty, pregnancy, periods and menopause, says Angela Holliday-Bell. But in most cases, people with little sleep “do well” simply because their brains have adapted to chronic sleep restrictions. “Over time, your brain adjusts its expectations of what feels ‘normal,’ so the fog and bad mood that comes with short sleep feels normal,” she adds.
The “new normal”
When you’re constantly sleep-deprived, your brain essentially recalibrates itself. “Even if you are cognitively and physiologically impaired, you don’t necessarily feel tired because over time you lose the ability to accurately perceive your own impairment,” says Dr. Matsumura. In most cases, people don’t realize how tired they really are until they start getting enough sleep.
The adrenaline illusion
In addition, you will probably be carried by adrenaline and momentum. “Stress hormones and alertness pathways can provide a temporary boost when you’re tired, causing your body to release cortisol and adrenaline to keep you moving, which can make you feel more alert even if you haven’t had enough sleep,” says Dr. Holliday Bell. This hormonal boost can temporarily mask fatigue, but is not a permanent solution because chronically elevated stress hormones increase inflammation, impair glucose metabolism (when your cells break down sugar to produce energy), and put stress on the cardiovascular system, adds Dr. Matsumura added.
Quality over quantity
It’s also worth noting that some people are simply less affected by sleep loss because they have higher sleep efficiency, which is the percentage of time they actually sleep in bed, says Morgan Soffler. As a result, they fall into deep sleep more quickly and ultimately spend more time in the phases in which memory, learning and recovery are particularly important. You feel refreshed and recharged after fewer hours, while someone else may need more time in bed overall to get enough restful sleep, she explains.
That being said, feeling “good” and not being tired are not the same as functioning optimally. Therefore, it is still very important to prioritize seven to nine hours of sleep per night. “For most people, it’s habit, adrenaline, or a busy lifestyle that forces them to persevere that they get by on short sleep, but they don’t really recognize the deficits in the long term,” says Dr. Holliday Bell. Speaking of which…
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What can happen if you get under seven hours?
A night or two of poor sleep won’t hurt you, but chronic sleep deficiency, defined as regularly getting less than six hours of sleep a night, can have serious long-term effects on your health, says Dr. Soffler.
“When you consistently miss your sleep goal, your brain has a hard time storing memories, regulating emotions, and keeping attention steady,” she says. “The body ends up with higher stress hormones, increased inflammation, and greater stress on the heart and metabolic system.”
Here’s a closer look at what happens to your brain and body when you don’t meet your sleep goal regularly:
Deterioration in mental health and possible mood disorders
Lack of sleep affects your emotions, making you not only tired but also more likely to be irritable—two things that can lead to depression and anxiety over time, says Dr. Soffler. “You may not feel unhappy every day, but your mood is slowly declining,” she says. A 2023 review by the American Psychological Association examined studies on the connection between sleep loss and emotions based on 50 years of research. It turns out that lack of sleep leads to fewer positive emotions such as joy, happiness and contentment, while at the same time increasing anxiety symptoms such as rapid heartbeat and uncontrolled worry.
Cognitive impairment
When you’re sleep-deprived, neurological pathways slow down, leading to shorter reaction times and a weakened mental state, according to a 2023 study in Neuroscience. This can lead to impaired attention, working memory, attention, judgment and decision-making in the short and long term.
Weakened immune function
Sleeping is how the body heals and regenerates itself, and those who repeatedly sleep less than six hours a night are more susceptible to colds, flu and infections, says Dr. Matsumura. “Regularly falling below six hours leads to significant impairment of the immune system in a way that has been consistently demonstrated in research,” she explains. Lack of sleep impairs immune function and promotes chronic inflammation, which weakens your body’s defenses and increases your risk of disease, according to a 2021 study in Communications Biology.
Increased risk of chronic diseases
Regular sleep of less than six hours disrupts hormone balance, increases blood pressure and triggers inflammation in the body, which can increase the risk of chronic diseases such as heart disease, diabetes, obesity and even cancer, says Dr. Matsumura. Research supports this: A 2024 study in Nature Medicine examined sleep patterns and chronic disease risk in nearly 7,000 participants over a period of 2.5 to 6.5 years. Poor sleep has been found to be associated with an increased risk of all-cause mortality and the development of chronic diseases.
In other words, when sleep suffers, every part of you suffers. The good news: Even if your sleep is poor right now, you can improve it. “Many of the effects of sleep deprivation are at least partially reversible once adequate, consistent sleep is restored and cognitive function, mood regulation, and immune response begin to improve, often within days to weeks of better sleep,” says Dr. Matsumura. “Restoring hormonal balance and metabolic health can take longer, sometimes several weeks to months, depending on how long the sleep deprivation has been going on, but it is possible to get the body back on track.”
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This is how you score with solid, high-quality Zzz’s:
Dr. Holliday-Bell recommends avoiding caffeine in the early afternoon, establishing a regular relaxation ritual, and creating a cool, calm, dark sleep environment to help your body settle into a healthy resting phase.
Another pro tip: Wake up at the same time every day. “Going to bed earlier doesn’t automatically mean you’ll fall asleep earlier, but waking up at the same time every day helps regulate your body clock and makes it easier to fall asleep the following night,” says Dr. Matsumura. “I also encourage people to stop trying to force sleep. So if you’re lying awake in bed for more than 20 minutes, getting up briefly and doing something quiet in dim light can actually help your brain re-associate bed with sleep rather than frustration.”
Remember: Sleep is restorative, so you’ll notice the greatest gains in energy, mental clarity, and overall well-being when the right amount of sleep is paired with conditions that actually allow your body to recover.
This article by Andi Breitowich was originally published on Women’s Health US.
