It is commonly accepted that an individual should ideally get eight hours of sleep on a nightly basis. However, there are dissenting voices among experts about exactly how much sleep is best.
It’s somewhat obvious that getting too little sleep is unhealthy, and we can easily see the symptoms of fatigue in ourselves and others. Research conducted for the past several years now shows that too much sleep could be equally if not more detrimental: there is a gradual increase in mortality risk in individuals who sleep more than the average nightly six-to-eight-hour range.
Professor Franco Cappuccio, professor of cardiovascular medicine and epidemiology at the University of Warwick, aggregated the information from 16 different sleep-related studies involving more than one million people. Participants were grouped into broad categories based on how many hours of sleep they got on average. Cappuccio found that analysis showed that 12% of the subjects who slept “too little” had died by the time of follow-up, as opposed to 30% of the subjects who slept “too long.” What this means in layman’s terms is that nine of hours of sleep could be more harmful than five hours.
Cappuccio reasoned that sleeping more than 6-8 hours a night could have some correlation to depression, illness or medication. After taking this into account statistically, the ratio was still skewed in favor of less sleep. He concluded that people who are “over-sleeping” most likely have an underlying health problem, in many cases, which could account for the high mortality rate. Therefore, the larger amounts of sleep are not a cause but a symptom of reduced health.
However, some research does indicate that excessive sleep could actually be a causation factor in poor health. A small study conducted by Professor Shawn Youngstedt of Arizona State University asked 14 teenagers to sleep an extra few hours every night for a prescribed period of time. The subjects all showed increased levels of depressed feelings, increased levels of inflammation in blood tests as well as increased soreness and back pain.
Sleep and its effects are very difficult values to measure, and tests often rely on verbal accounts from subjects, which are not solid numbers. Furthermore, feelings of tiredness are subjective, and groups like teenagers, children and seniors all generally need more sleep than middle aged people.
So, is there any way to know what the best amount of sleep really is, in general? Prof. Cappuccio says 3/4 of people in Western societies sleep between six and eight hours a night, making it a de-facto consensus. That’s not to say, however, that you might live optimally with nine or five hours. Everybody is different, making speaking in generalities quite difficult.
According to Dr. Gregg Jacobs, a researcher at the Sleep Disorders Center at the University of Massachusetts Medical School, the magic number of sleep might just be seven hours.
“The typical adult today (according to the National Sleep Foundation’s annual poll) reports seven hours of sleep per night. 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.”