Less dramatic forms of bi-phasic sleep are evident in today’s society, for example in cultures that take an afternoon siesta. Our body clock lends itself to such a schedule, having a reduction in alertness in the early afternoon (the so-called “post-lunch dip”).
In the early 1990s, psychiatrist Thomas Wehr conducted a laboratory experiment in which he exposed a group of people to a short photoperiod – that is, they were left in darkness for 14 hours every day instead of the typical eight hours – for a month.
It took some time for their sleep to regulate but by the fourth week a distinct two-phase sleep pattern emerged. They slept first for four hours, then woke for one to three hours before falling into a second four-hour sleep. This finding suggests bi-phasic sleep is a natural process with a biological basis.
Pros And Cons
Today’s society often doesn’t allow for this type of flexibility, thus we have to conform to today’s sleep/wake schedules. It is generally thought a continuous seven to nine-hour unbroken sleep is probably best for feeling refreshed. Such a schedule may not suit our circadian rhythms however, as we desynchronise with the external 24-hour light/dark cycle.
To successfully maintain a split sleep schedule, you have to get the timing right – that is commencing sleep when there is a strong drive for sleep and during a low circadian point in order to fall asleep quickly and maintain sleep.
Some of the key advantages of a split sleep schedule include the flexibility it allows with work and family time (where this flexibility is afforded). Some individuals in modern society have adopted this type of schedule as it provides two periods of increased activity, creativity and alertness across the day, rather than having a long wake period where sleepiness builds up across the day and productivity wanes.
In support of this, there is growing evidence suggesting naps can have important benefits for memory and learning, increasing our alertness and improving mood states. Some believe sleep disorders, like sleep maintenance insomnia, are rooted in the body’s natural preference for split sleep. Therefore, split sleep schedules may be a more natural rhythm for some people.