Many of us complain that we are not getting enough sleep. We try and fail to get the golden eight, which is widely assumed to be the ideal amount of sleep. However, according to a recent article from the BBC, eight hours of sleep is too much and may actually be harmful to your health.
We all know that getting too little sleep is bad. You feel tired, irritable, and it can contribute to obesity, high blood pressure, diabetes, and heart disease, doctors say. However, research carried out over the past 10 years appears to show that adults who usually sleep for less than six hours or more than eight are at risk of dying earlier than those sleep for between six and eight hours.
Prof Franco Cappuccio, professor of cardiovascular medicine and epidemiology at the University of Warwick, has analyzed 16 studies, in which overall more than a million people were asked about their sleeping habits and then followed up over time. Cappuccio put the people involved into three broad groups:
• those who said they slept less than six hours a night
• those who said they slept for between six and eight hours
• those who said they slept for more than eight hours
Cappuccio found that 12% more of the short sleepers had died when they were followed up, compared to the medium sleepers. However, 30% more of the long sleepers had died, compared to the medium sleepers. That’s a significant increase in mortality risk, roughly equivalent to the risk of drinking several units of alcohol per day, though less than the mortality risk that comes from smoking.
But can it really be true that getting nine hours’ sleep is worse for you than getting five? Cappuccio was aware of the possibility that people sleeping too long might be depressed, or might be using sleeping pills. He corrected for this, though, and found the association was still there. His own theory is that people who sleep for more than eight hours sometimes have an underlying health problem that is not yet showing in other symptoms. So, it’s not the long sleep that is causing the increased mortality risk, it’s the hidden illness.
But not everyone agrees. Prof Shawn Youngstedt of Arizona State University carried out a small study involving 14 young adults, persuading them to spend two hours more in bed per night for three weeks.
They reported back that they suffered from “increases in depressed mood” as Youngstedt puts it, and also “increases in inflammation” – specifically, higher levels in the blood of a protein called IL-6, which is connected with inflammation.The participants in the study also complained about soreness and back pain. This makes Youngstedt wonder whether the problem with long sleep is the prolonged inactivity that goes with it. Until the late 17th Century people did not sleep in one long uninterrupted stretch, but in two segments, separated by a period of one or two hours in which they prayed, read, chatted, had sex, smoked, went to the toilet or even visited neighbours. That may be more natural than the current tendency to sleep – or try to – in one stretch. Youngstedt has now been carrying out an experiment where long-sleeping and average-sleeping adults are asked to spend an hour less in bed each night. The results will be published soon, he says.
So if sleeping for over eight hours is too much and sleeping for less than six hours is too little, what is the ideal amount of sleep? The magic number, according to Dr Gregg Jacobs, of the Sleep Disorders Center at the University of Massachusetts Medical School, may actually be seven. “Seven hours sleep keeps turning up over and over again,” he says. He points, for example, to the National Sleep Foundation’s annual poll of a random sample of adults in the US. “The typical adult today [in that poll] reports seven hours of sleep. And that actually seems to be the median sleep duration in the adult population around the world. That suggests there’s something around seven hours of sleep that’s kind of natural for the brain.”