Lots of us struggle to get enough shut-eye—but too much sleep isn’t good for you, either. Click through the slide show above to see why it’s bad to OD on z’s, and how to find the sandman’s sweet spot.
You’re at greater risk for heart disease and stroke
The negative health effects of too little sleep are well-documented, but what happens from sleeping too much is less clear. The National Sleep Foundation recommends that the average adult get seven to nine hours of sleep. But what if your body craves more sleep: Can you get too much? A growing body of research connects oversleeping with bad health outcomes.
‘Oversleeping is not harmful in and of itself, but it is a sign that you may be sleeping ineffectively, or that there is another problem requiring more sleep,’ says Carl Bazil, MD, director of the division of sleep and epilepsy at New York-Presbyterian/Columbia University Medical Center. ‘There are also otherwise normal people who are ‘long sleepers’—they function perfectly well if they get nine or 10 hours but are sleepy on less. It’s still important, however, to check for other possibilities.’
You might not be sleeping well
One theory about why sleeping too much is linked with other health problems is that your time in bed is disrupted, so you’re not actually getting good rest. ‘Those with untreated sleep apnea [a common breathing problem] have a tendency to oversleep, and we know that undiagnosed and untreated sleep apnea leads to both heart disease and stroke,’ says Michael J. Breus, PhD, a clinical psychologist known as The Sleep Doctor.
He says other problems like stomach upset or hot flashes could also be the cause of poor sleep, or your environment might not be dark or quiet enough. Even teeth grinding can cause you not to sleep as well. If you feel that you’re still sleepy even though you’ve been in bed a long time, talk to your doctor to tease out the cause.
You’re more likely to be obese
Weight gain is another chicken-or-egg factor associated with long amounts of sleep. ‘One difficulty in untangling these effects is that things like sleep-disordered breathing, depression, or medication side effects can cause an increase in sleep duration and are also linked to other risk factors, such as weight gain,’ says Elizabeth McDevitt, PhD, a researcher at the Sleep and Cognition Lab at the University of California, Riverside.
You could develop diabetes
Not surprisingly, given the link between longer sleep and obesity, diabetes is also more common among long sleepers. But Canadian researchers found that even after adjusting for body mass, long sleepers had double the risk of developing diabetes. Other studies suggest that too much (or too little) sleep can affect your blood glucose levels, regardless of your weight or activity level.
Still, a cause has not yet been definitively proven. ‘Very little is understood about mechanistic pathways linking long sleep and health outcomes,’ Dr. McDevitt says.
You could start getting headaches
You know that feeling when you sleep in, only to wake up groggy and headachy, almost like you have a hangover? Although that could be caused by poor sleep, it also could be one of the side effects of sleeping too much.
‘The mechanism behind this isn’t understood that well, and one hypothesis is that fluctuations in neurotransmitters during sleep may be a trigger for headaches,’ Dr. McDevitt says. ‘Another possibility is that when people sleep later in the morning, they may be sleeping past their normal breakfast or coffee time, and the headaches may be related to caffeine withdrawals, low blood sugar, or dehydration.’
You’re more likely to be depressed
One symptom of depression is oversleeping, so having untreated mental health problems could be one reason why you’ve had a hard time getting up. Studies have shown long sleep is significantly associated with frequent mental distress. Another study, done in twins, found that long sleep actually activated genes related to depressive symptoms.
‘One hypothesis is that long sleep duration is associated with decreased physical activity,’ Dr. McDevitt says. ‘Physical activity has been associated with reduced risk of depression by increasing levels of the neurotransmitters dopamine and serotonin, increasing release of endorphins, distracting from stressful stimuli, and improving self-esteem.’