Good quality sleep is linked to overall physical and mental health, but is too much sleep harmful? Simply put, it can be. Excessive sleep, as well as lack of it, is linked to a higher risk of chronic diseases, including coronary heart disease, type 2 diabetes, anxiety and obesity in adults over the age of 45, according to a study published in PLoS one (opens in new tab).
But why is sleep important? Teresa Schnorbach (opens in new tab)psychologist and sleep scientist specializing in clinical psychology and cognitive neuropsychology, tells Live Science that it’s critical to maintaining our physical and mental well-being.
“It’s essential for regulating metabolic and hormonal processes in the body,” she says. “It also serves a restorative purpose by flushing out toxins that have accumulated in the brain. Sleep also strengthens our immune system by allowing specialized immune cells to work more effectively in fighting infections.
Not to mention that it can also help us heal emotional wounds. “During rapid eye movement (REM) sleep, which typically occurs about 90 minutes into the sleep cycle, concentrations of the stress-related, anxiety-inducing chemical norepinephrine shut down in the brain,” says Schnorbach. “At the same time, the brain’s emotion and memory-related structures are reactivated, helping us process upsetting memories or experiences.”
You can monitor your sleep using one of the best fitness trackers or sleep apps, but ironically, if you spend too much time sleeping, you’re likely to wake up feeling tired and lethargic. This is because any significant deviation from normal sleep patterns can disrupt the body’s internal rhythm and increase daytime fatigue. Here we’ll find out more about what happens when you fall asleep and exactly how much sleep you should be getting.
How much sleep should you get a night?
Dr. Guy Meadows, Clinical Director and Co-Founder of Sleep School (opens in new tab)says that sleep is our natural way to recharge, restore and even detoxify our body and mind from the efforts and stress of the previous day, preparing us to perform at our best again and again.
But how much sleep you need depends on your age, activity level, general health and lifestyle, and this figure will change over the course of your life.
In general, the Centers for Disease Control and Prevention (CDC) recommends seven to nine hours for adults, eight to ten hours for teenagers, and 14-17 hours for newborns. During times of stress or illness, you may feel that you need more sleep than usual.
Dr. Guy Meadows, PhD, is a British sleep expert and co-founder of the Sleep School (opens in new tab). Meadows has studied human physiology for 25 years, 20 of which have been devoted to sleep research and the prevention of sleep disorders. He has worked with thousands of insomnia sufferers over the past 10 years and created the Sleep School to help insomnia sufferers with an evidence-based solution.
Meadows says, “People often think we can train ourselves to need less sleep, but as convenient as that is, it’s unfortunately not true. Science tells us that we simply cannot change the amount of sleep we need.
“Contrary to popular belief, older people don’t actually need less sleep; their sleep patterns may change as well as the structure of their sleep, but their need for sleep remains the same.
Unfortunately, however, the rise of sleep-disrupting medical conditions, such as night pain or increasingly frequent trips to the bathroom, makes it difficult to achieve uninterrupted sleep. According to Meadows, if you want good mental health, make sleep a priority and aim to get the right amount for you.
Diabetics often experience fatigue due to high or low blood sugar levels, so to stabilize them, they should aim for at least seven hours of sleep a night.
The CDC says signs of poor sleep quality include not feeling rested even after a lot of sleep, waking up repeatedly during the night, and experiencing symptoms of sleep disorders (such as snoring or gasping).
Can you sleep too much?
Sleep is a time when the body repairs and rebuilds, and like not getting enough sleep, sleeping too much can lead to a host of health problems. Meadows says, “Sleep regulates our appetite hormones, helping us maintain a healthy weight. Research also shows that while we sleep, our brain flushes out any toxins it has built up during the day, reducing the risk of Alzheimer’s disease.
Sleep also plays an important role in maintaining our blood sugar levels and therefore our risk of diabetes. “A good night’s sleep is also known to have a therapeutic effect, removing the stress of the day and helping us wake up happier,” adds Meadows. “It also preserves our prefrontal cortex, the area of the brain responsible for many of our higher-order executive functions, such as focusing, problem-solving and decision-making.”
But can you sleep too much? Yes, says Schnorbach. “There will be times when you may need more sleep than others, such as when your body is fighting an illness, but in general you can think of the relationship between sleep and health, or graphing it as an inverted U shape; there is such a thing as a ‘golden ratio’ and neither too little nor too much is recommended.’
Teresa Schnorbach is a psychologist and sleep scientist specializing in clinical psychology and cognitive neuropsychology. She has completed postgraduate training in Cognitive Behavioral Therapy for Insomnia (CBT-I) with the German Sleep Society, approved by the European Research Society.
When is oversleeping a problem?
The “right” amount of sleep can be a bit subjective – some people feel fantastic after seven hours, while others may need a bit more.
According to the Sleep Foundation, oversleeping (also known as long sleep) is defined as sleeping more than nine hours, a period of time that most experts agree is excessive for adults.
Sleep disorders
“Oversleeping is often associated with physical or mental disorders, such as sleep apnea, depression, or medication side effects, and effects that can be linked to oversleeping, including diabetes, heart disease, obesity, and mental illness,” Schnorbach told Live Science.
Hypersomnia – the opposite of insomnia – is a condition in which you simultaneously sleep and feel overly sleepy during the day. Narcolepsy and other sleep disorders often cause hypersomnia.
Meadows says: “Hypersomnia is characterized by excessive daytime sleepiness, where you may feel the urge to sleep longer than necessary and yet wake up tired. Hypersomnia can be primary and secondary. Primary means that there is usually no identifiable cause; secondary suggests that the cause may be other medical conditions, mental health problems, medications, sleep disorders, or lack of sleep due to shift work.
Impaired brain function
Too much sleep – more than eight hours – can have a detrimental effect on the brain, according to the world’s largest sleep study published in the journal Sleep. Neuroscientists at Western University’s Brain and Mind Institute found that too much shut-eye can reduce cognitive and reasoning skills.
Weight gain
Research published in Sleep (opens in new tab) found that people who slept nine to 10 hours a night were 21% more likely to become obese over a six-year period than those who slept seven to eight hours. The relationship between sleep time and obesity was the same even when food intake and exercise were taken into account.
Depression and mental health
Oversleeping is a possible symptom of depression and anxiety and can make things worse. A study published in Sleep Medicine Reviews (opens in new tab) found that long sleepers have a higher rate of depression.
Lifestyle factors
If you’re not getting enough sleep due to lifestyle factors, such as drinking too much alcohol or taking certain prescription medications, your body tries to compensate by sleeping. Studies (opens in new tab) have found that too much sleep may play a role in increased inflammation in the body, which is linked to an increased risk of many health conditions from diabetes to Alzheimer’s.
“Bad lifestyle habits that negatively affect sleep quality and duration include excessive consumption of caffeine, alcohol, sugar and nicotine, as well as lack of exercise,” says Meadows. “Lead a healthy lifestyle that promotes sleep. Aim to drink no more than two to three caffeinated drinks a day and switch to herbal or caffeine-free alternatives at lunchtime. Be active every day, choosing aerobic exercise such as walking, dancing or jogging over weight training or sprinting. Aim to leave at least two hours between your workout and bedtime to allow your core body temperature to cool down.
If you’re sleeping too much, Schnorbach suggests reviewing your lifestyle to see if there are any habits that could be affecting your sleep quality and making you sleepy.
“I would also recommend talking to a doctor or health professional, as excessive sleeping can be a symptom of a physical or mental health problem,” she says.
This article is for informational purposes only and is not intended to offer medical advice.