When people talk about having “too much of a good thing”, they usually mean overindulging in something like ice cream or fast food – things you probably enjoy, even if they aren’t that good for you. But what about something that’s objectively important to your health and well-being, like sleep? Well, it turns out that you can get too much of that, too. It’s a little hard to believe that there’s such a thing as sleeping too much, since so many of us feel like it’s a struggle to get barely enough, but it’s true – you can sleep too much.
Too much sleep can lead to depression risk
Most people need 7-9 hours of sleep, and oversleeping is connected to health problems like depression, heart disease, and diabetes. A 2014 study of 894 pairs of twins, for example, showed that the genetic risk of depression was higher in subjects who got less than 7 hours of sleep, or 9 or more hours of sleep every night. A 2012 study found that among elderly women sleeping too much or too little worsens the brains’ functioning over a six-year period. Women who slept more than nine hours each night or fewer than five displayed changes in their brains on par with aging two years. Meaning, people who underslept or overslept were more likely to be depressed because of genetic factors, as opposed to environmental ones.
Harder to get pregnant
In 2013 a Korean research team analyzed the sleep habits of more than 650 women undergoing in vitro fertilisation. They found that pregnancy rates were highest among the women who got seven to eight hours of sleep a night and lowest in women who got 9 to 11 hours.
Increase diabetes risk
Sleeping too much can substantially increase diabetes risk. Another study, published in 2009, followed 276 subjects for six years and found that people who slept more than eight hours a night were twice as likely to develop type 2 diabetes or impaired glucose tolerance over a six-year period than people who slept between seven or eight hours a night, even after controlling for differences in body mass!
Sleeping too much can lead to weight gain
The same researchers also looked at body weight gain among adults over a six-year period they found that short and long sleepers gained more weight over the six years than people who slept seven to eight hours a night. People who slept 9 to 10 hours each night were 25% more likely to have gained 5 kilos over the study period even after controlling for food intake and physical activity.
It can can hurt your heart
In research presented at a 2012 American College of Cardiology meeting, sleeping eight or more hours a night was linked to an increased risk of heart problems. The researchers analyzed data from over 3,000 people and found that long sleepers had two times the risk of angina and 1.1 times the risk of coronary artery disease. And according to a study on the sleep habits of 400,000 Taiwanese adults, the risk of coronary heart disease is about the same in people who sleep less than 4 hours a night as it is in those who sleep more than eight hours a night. Subjects who underslept had a 35% higher risk of heart disease, and people who overslept had a 34% increase.
A 2013 study of about 54,000 adults over the age of 44 found links between too much sleep and increased rates of heart disease, diabetes, obesity, stroke, and mental health issues. In fact, the rates of coronary heart disease, diabetes, and stroke were even higher in people who overslept than in those who slept too little.
So, there is something here. Sleep correlates with all kinds of health problems. But it’s hard to say whether too much sleep actually causes these issues. It’s totally possible that oversleeping is actually a symptom of things like depression or heart disease, or that there’s some other connection. Either way, consistently sleeping too much might be a bad sign. Sleep tight! (and short)