In the summer of 2015, The New Yorker published a series of articles on sleep, citing scientific studies and research that people are sleeping less and less and adding new material to a debate that sees proponents of the classic eight-hour sleep noticeably separated from those who sleep less. Usually, proponents of getting 6 hours of sleep per night believe this sleep time is necessary to recover energy, but the theory clashes with modern scientific studies.
Sleep 6 hours a night: What does science say?
According to research conducted in 2003 at the University of Pennsylvania Medical School in Philadelphia (USA), six hours of sleep a day is not enough and in some cases is equivalent to no sleep at all. The study involved 48 volunteers who were assigned sleep for a maximum of four, six, or eight hours a night for two weeks. The researchers also asked a group of participants not to sleep at all for three consecutive days, in order to compare their level of fatigue with that of the other volunteers.
The experiment was conducted in the laboratory, in order to keep as many variables as possible under control, and of course the behavior of the volunteers, who woke up to different types of tests every two hours to assess their cognitive abilities in relation to the number hours of sleep. Each participant was asked to describe their unusual mood and symptoms, if any. Some research results confirmed the initial hypotheses of the researchers, others were more surprising.
The group of eight hours of sleep a day is the one who has done better, obtaining a higher average in all the tests carried out to verify the degree of reactivity and concentration. The volunteers who were asked to sleep only four hours a night obtained very poor results, while those who had to sleep 6 hours a night did well, but only during the first ten days of the experiment. Over the past few days, cognitive tests on volunteers who slept 6 hours were very negative and comparable to those of the group that had been asked not to sleep for three consecutive days. The decline in cognitive performance also occurred for the four-hour sleep group, but as expected, it occurred earlier.
The researchers also noted that members of the six-hour group tended to underestimate their level of fatigue, despite cognitive tests indicating a significant decline in their ability to concentrate and perform certain tasks. While volunteers who were asked not to sleep for three days reported a increased levels of fatigue, up to twice as high as at the start of the test, those in the group that had to sleep 6 hours a night did not indicate an increase of one level of fatigue, although the tests indicated comparable performance to those of people who had not completely slept. In short, those who slept six hours a night at some point were tired and not as alert as those who hadn't slept at all but didn't notice:
As they recall from Fast Company, the Philadelphia research seems to confirm a feature discovered in other studies: each of us tends to overestimate the number of hours we have spent sleeping. A 2008 study found that most people are confident, on average, that they've slept 48 minutes longer than before. The researchers also noted that for every hour of sleep beyond the first six, most people tended to overestimate time spent in bed by at least half an hour. This means that many people convinced to sleep seven hours a night actually do not exceed six hours. The causes can be many and include going to bed later than planned, unconsciously suppressing the delay, taking a long time to fall asleep, or having many nighttime awakenings.
What to conclude?
Other studies have looked at long-term partial sleep deprivation, but the results of the Philadelphia study point more strongly than others to the relevance of the phenomenon. The biggest problem is related to everyone's perception of feeling rested, even if in reality it is not because of the few hours of sleep, with a consequent reduction in cognitive abilities. Fatigue of this type can be dangerous, especially if you are doing jobs where good reflexes are needed or the ability to maintain concentration for a long time.
Sleep studies are countless and in recent years there has been much discussion, in the scientific community and beyond, about the ideal number of hours of sleep each day to stay fit and rested. Many studies put an average value around 8 hours, but other studies suggest that 7 is sufficient. In reality, an average figure does not offer much information: everyone has their own rhythm and sleeps differently.
Over the years, the advice of doctors and experts for better rest has remained substantially unchanged, and is often linked to common sense more than anything else: always go to sleep at the same time, do not use electronic devices with bright screens within half an hour before going to bed, sleeping in a dark, quiet, cool room avoiding the use of alcohol which makes you drowsy but does not help you rest, not eating alcohol heavy foods before bedtime, exercise regularly, and think about pleasant things before going to sleep.