Most people know about the dangers of sleep deprivation: too little sleep affects mood, cognitive function, and just about every system in the body (it even delays wound healing). If that sounds alarming, you should read our detailed account of what happens when you don’t get enough sleep to learn more.
But it turns out that sleeping too little isn’t the only thing you have to worry about. A new study suggests that sleeping too much can be just as dangerous, especially for your heart. Here, we’ll answer the question “how much sleep do you need” and explore the effects of sleeping too much or too little.
The dangers of sleeping too much
According to new research published in the Journal of the American Heart Association, people who reported getting too much sleep (more than eight hours a night) have a higher risk of mortality and heart disease. The risk increases as sleep exceeds the recommended seven to eight hours.
Researchers conducted a meta-analysis of 74 studies, with a total of over three million participants. They found that, surprisingly, long sleep durations were associated more with adverse health outcomes than short durations. In other words, too much sleep could be worse for the heart than sleeping too little! The authors even found that short sleepers had mostly the same outcomes as normal sleepers.
Making sense of the sleep science
Oversleeping is almost certainly dangerous, but if we looked at this research in isolation, we might think that the dangers of under-sleeping have been overblown. That’s not the whole story. In fact, this study has several limitations worth noting.
First, the study relies on self-reported sleep duration and quality. The researchers looked at several smaller studies and combined the data, but the data was all subjective to begin with. As a result, there’s no way to verify participants’ own accounts of whether they got too little or too much sleep. If someone says they sleep for eight hours a night, we have to take them at their word.
Second, this study looks at very specific outcomes: cardiovascular events and mortality. We have good reason to believe that sleep deprivation is linked to Alzheimer’s, among other things, but the study makes no mention of this. The omission makes sense, since this study was published by the American Heart Association, but we shouldn’t view the findings as comprehensive.
There is a mountain of research suggesting that sleeping for less than seven hours a night is profoundly harmful, and even if a new study seems to provide evidence to the contrary, we should be careful before throwing out conventional wisdom. You should always talk to your doctor before changing your behavior based on scientific research.
So, how much sleep do you need?
When it comes to answering the question “how much sleep do you need,” there’s no one-size-fits-all answer. There will always be slight variations from person to person. In addition, you need different amounts of sleep at different times in your life. Sleep science, unfortunately, is not yet an exact science.
However, on average, the Centers for Disease Control and Prevention, National Sleep Foundation, and American Sleep Association all recommend about seven to eight hours of sleep per night for adults between 18 and 60 years old. Anything less increases the risk of health problems. This is borne out regularly by new research every month.
The most important tip for a healthy sleep cycle is to maintain a regular schedule. Try to go to bed and wake up at the same time every day, weekends included. And although an alarm clock may seem helpful in this endeavor, you might want to think twice about using one.
To help you maintain healthy and consistent sleep, we’ve put together a list of our best sleep health content: