Doctors agree: Quality sleep is crucial for your health. Not only do you need it to stay focused and alert during the day, but it helps your body recharge and recover from wear and tear and might lower your risk of everything from obesity and diabetes to premature death. But can you have too much of a good thing? Definitely, say experts.
 
"Individuals who sleep more than 10 hours per day generally have worse health profiles than those who sleep 7 to 8 hours," says Susan Redline, MD, MPH, professor of sleep medicine at Harvard and senior physician in the division of sleep and circadian disorders at Brigham and Women's Hospital in Boston.  (Always dragging? Here are 7 reasons you're tired all the time.)

Nearly 30 percent of adults in the US are in this group of "long sleepers." Logging lots of shut-eye becomes more common as you get older, and it's not entirely clear whether it's a sign that you have a disease or if it can actually make you sick. "The predominant opinion is that long sleep is a marker for underlying health problems," says Redline.

But Michael Irwin, MD, Cousins Professor of Psychiatry and Biobehavioral Sciences at the David Geffen School of Medicine at UCLA, says that sleeping too much can also cause disease. That's because "long" sleep—which he defines as more than 8 hours—is usually poor sleep.  

"What we're really looking at is a group of people who are spending a long time in bed," says Irwin, who notes that these individuals might not be soundly asleep the whole time.  

The bottom line? Sleeping too much could turn out to be just as damaging as sleeping too little. Here are a few of the problems you might face if you regularly overdo it. (Feel better starting today with Rodale's The Thyroid Cure, a new book that's helped thousands of people finally solve the mystery of what's ailing them.)

You're at higher risk of heart disease.

If you snooze a ton, you lose...at least when it comes to heart health. Heart disease is already the number one cause of death in the US, and sleeping more than 8 hours a night increases your chances of dying from it by 34 percent.

Women are more prone to sleeping longer than men, which puts them at the highest risk of developing heart problems.

You're more likely to struggle with your weight.

Many studies show that people who don't sleep enough tend to be heavier, but there's also a link between excess sleep and obesity.

Though it's not a simple case of cause and effect, says Irwin, there's definitely a connection. "What we do know is that as people get more obese, they're likely to be long sleepers," he says. "And if you're a long sleeper, you're more likely to be obese." (Here’s how to start walking when you have 50+ pounds to lose.)

One theory is that too much sleep translates to too little exercise. "Long sleepers have shorter periods available when they can be active," says Redline. In other words, the more you sleep, the less you move—and the fewer calories you burn off.

You may develop diabetes.

Too much sleep can raise your blood sugar levels (as can skimping on sleep). That's not the kind of sweet dreams you want: High blood glucose can increase your risk of getting type 2 diabetes.

Again, being more sedentary—and overweight—is likely what's driving this risk factor, says Redline. (Finally get the abs you want with these 9 proven ways to lose stubborn belly fat.)

Your brain gets fuzzier.

Can't concentrate? Blame your time between the sheets. Chronic long sleeping can age your brain by as much as 2 years and make it difficult to perform everyday tasks, according to research published in the Journal of the American Geriatrics Society.

Irwin says the fact that long sleepers tend to have trouble with basic mental functioning may have to do with how often they wake during the night. If you're getting up too frequently, you might not be getting enough of the deep, restorative sleep you need.

You're at risk of dying early.

It's scary, but true: Large-scale epidemiologic studies have shown that people who sleep longer are more likely to die prematurely. No one knows exactly why, but inflammation probably plays an important role, says Irwin. Plus you're more likely to expire at a younger age if you have problems like diabetes and heart disease—which are tied to too much (or too little) sleep. (Send your blood pressure in the right direction by eating these 13 power foods that lower BP naturally.)

Your mood can suffer.

Depression and sleep go hand in hand, but it's a chicken-and-egg situation. Often, says Irwin, people with certain types of depression sleep longer. And longer sleep can make depression worse.

It's important to note that feeling blah may be temporary, and not everyone who gets too much sleep and feels lousy is clinically depressed. In some cases, shortening your snoozes might be enough to lift your spirits, says Irwin. 

This article originally appeared on Prevention.com.