Almost all species on earth need sleep to function optimally, and we humans are no exception. But, how much sleep do we really need to function best? This question has been the subject of considerable debate over a few decades now. Some research even suggests nighttime sleep in humans used to happen in 2 chunks, that is, people used to sleep for 4 hours, wake up for a couple of hours to do active or passive activities, and then return to sleep for another 4 hours. This pattern of sleep, however, began to change in the 17th century—Stephanie Hegarty nicely describes this in this BBC report.
Why is it that in our current society sleeping anything more than 5 hours per night is considered a luxury? Long work hours in jobs requiring little or no physical strain, higher computer/television/smartphone use, lower physical activity levels, stress of related to work and family responsibilities, as well as an active social life are partly to blame.1–3 Poor diet is another obvious factor, but genetics is not.
So for adults at least, the American Academy of Sleep Medicine and Sleep Research Society recently developed a recommendation of at least 7 hours of sleep per night on a regular basis for optimal health.4 Also recently, the National Sleep Foundation lowered its recommendations for adults to include 6 hours of sleep as ‘may be appropriate’. This is clear evidence that the sleep experts cannot agree still; and, it sends mixed messages to the public.
A positive note is, however, the US Center for Disease Control and Prevention now recognizes short sleep as a public health epidemic,5 Therefore, more public health promotion activities to improve sleep duration are likely. In fact, one of the goals of the National Healthy Sleep Awareness Project is to increase the number of adults getting sufficient sleep by 20204 because sleep duration in adults has been decreasing. A typical adult in the US slept about 2 hours more in the 1960’s than in 2002.6 Compared to the 1980’s, twice as many adults are sleeping 6 hours or less per night7 (that is, one in 3 adults are sleeping 6 hours or less per night8). This is really concerning because we know that inadequate sleep, i.e., sleeping less than 7 hours per night on a regular basis,4 is compromises our physical, emotional, and cognitive well-being.9-11