Does polyphasic sleep work? Does it have long-term or short-term side effects?

Question

Cutting sleep down to 6, or 4, or 2 hours per day sounds fantastic. It also sounds like something that should have evolved naturally if it were possible.

From the Polyphasic Society:

Humans are naturally polyphasic sleepers. Depending on the culture, humans will either have segmented night sleep, or nap throughout the day.
The reason humans sleep polyphasically is to improve sleep density, sleep stability, and for the warriors out there decrease overall time asleep. Humans need sleep, but only certain stages of sleep are important for us to recover each night.

Has any serious research been done into polyphasic sleep and its side effects?

Polyphasic sleep involves sleeping more than once per day at regular intervals and for regular amounts of time. There are different specific regiments, but the overall goal is usually to reduce the total time spent sleeping.

Answer 1

There is little research published in scientific journals about conscious adoption of extreme sleep patterns.

In 2000 PureDoxyk proposed the Uberman schedule: Every four hours you sleep 20 minutes.

It takes a lot of willpower to adopt a sleep pattern like Uberman that only allows 2 hours of sleep per day. People need a deep inner desire to adopt such a schedule or there will be no compliance with the experimental setup.

Most people who try to adopt the Uberman schedule fail very soon. There are some such as Steve Pavlina or Tynan claim to have followed the schedule and produced a detailed account of the experience at their website. Steve Pavlina quit the schedule after 5 1/2 months. Tynan quit after 4 1/2 months. PureDoxyk quit after 6 months. They all cite impracticality of having to sleep every 4 hours as reason for quiting.

There's a Time article from 1943 that reports Buckminster Fuller to have spent two years on a polyphasic sleep shedule with two hours per day he called dymaxion sleep.

To my awareness there's no contemporary person who upheld the schedule for multiple years.

Even if it's possible to keep up with the Uberman schedule it doesn't seem to worthwhile or those people would probably have continued with it.

As far as short term side effects goes there seems to be mental effects. We unfortunately don't have much more than self reporting about most of the polyphasic sleepers. I will therefore write a bit which is my own understanding from reading about polyphasic sleep.

A lot of polyphasic sleepers report to be more productive during the time they are on the schedule. Polyphasic sleep forces you to do detailed time management or you screw up. The forced time management might account for the gain in productivity.

It's my understanding that the mental state is similar to the state of calmness, that's reached through doing a lot of meditation. The sleepers might therefore perform better on some tasks.

On the other hand long deep problem solving such as making mathematical proofs might suffer.

In a lot of the polyphasic sleep writing you find the claim that those who practice the Uberman schedule are in the REM state when they sleep. It's my understanding that Claudio Stampi showed in Why We Nap: Evolution, Chronobiology, and Functions of Polyphasic and Ultrashort Sleep that this isn't what happens when people adapt to short nap based sleep.

What about sleeping 6 hours? There was a huge study that concluded that people who sleep 6 hours have a longer life span than those that sleep 8 hours. Correlation isn't causation and this doesn't mean that you will be healthier when you cut your sleep to 6 hours. It however makes it plausible that a 6 hour sleep schedule could be healthy.

If you want to understand more about polyphasic sleep cycles there's a mailing list and a forum. The forum is run by the Zeo guys who produce equipment to measure sleep states. With a bit of luck they will be able to gather enough data in the coming years to publish a bit on polyphasic sleep schedules.

it also sounds like something that should have evolved naturally if it were possible.

The ability to stay awake for 12 hours without pause is quite valuable. People who practice the Uberman schedule lose the ability. If you are a hunter gatherer you don't profit very much from being awake at night. It's harder to protect yourself when you don't stay near the fire that your tribe lighted during the night. I would note that the sleep practices of a person in the western world who sleep in a bed without a nearby fire are very different from the sleep practices according to which we developed.

Answer 2

The Wikipedia article on polyphasic sleep gives some interesting pointers such as this study for the NASA:

NASA, in cooperation with the National Space Biomedical Research Institute, has funded research on napping. Despite NASA recommendations that astronauts sleep 8 hours a day when in space, they usually have trouble sleeping 8 hours at a stretch, so the agency needs to know about the optimal length, timing and effect of naps. Professor David Dinges of the University of Pennsylvania School of Medicine led research in a laboratory setting on sleep schedules which combined various amounts of "anchor sleep," ranging from about 4 to 8 hours in length, with no nap or daily naps of up to 2.5 hours. Longer naps were found to be better, with some cognitive functions benefiting more from napping than others. Vigilance and basic alertness benefited the least while working memory benefited greatly. Naps in the individual subjects' biological daytime worked well, but naps in their nighttime were followed by much greater sleep inertia lasting up to an hour.

But David Dinges (major American sleep researcher) concludes:

Dinges notes another finding of their study: Naps are a short-term fix, offering only temporary boosts in mental acuity. "They cannot replace adequate recovery sleep over many days," he says. In the end, there's no substitute for 8 sweet hours of shut-eye.