Can you train yourself to sleep less? Perhaps surprisingly the answer may be yes. Experiments in sleep restriction show some ability to voluntarily reduce sleep time, although only to some extent and the results are not foolproof. Normal 8-hour sleepers are able to reduce to 6 hours. Deep sleep time remains unchanged. Six hours appears to be the minimum for most people. A study in the UK showed that reducing the amount of sleep did not result in more productive working time. People just wasted the time spent awake.
A story holds that Leonardo da Vinci took 20 minute naps every two hours. His paint dried after 30 minutes. Solo seafarers do something like this. In an ongoing regimen the 20-minute sleep periods become more intense than the typical afternoon nap, and include some deep sleep which the average short nap does not. Note that people, including Leonardo apparently, do this a few weeks at a time, not indefinitely.
You can find a lot of people on the internet who have blogged about their experience with polyphasic sleep. As far as we can tell, not many people continue with this pattern over the long run.
Sure, you can do this; people do it all the time. Sleep is flexible enough that we can choose when we do it. As diurnal animals, humans more naturally sleep at night, but we have some control over when our main sleep period occurs and people adapt to the demands of shift work and family constraints. This hardly counts as a hack. If you talk about changing your sleep time every day and trying to maintain a high level of performance, that counts as a hack.
Writing about efforts to reduce sleep needs, Jessa Gamble wrote "if there were a widespread disease that similarly deprived people of a third of their conscious lives, the search for a cure would be lavishly funded." No doubt that is true, but that sentiment brings up the question of whether attempts to shorten sleep time can or should be made. Attempts to modify the brain and fundamental behavior have yielded mixed results.
Some people regard sleep as lost or wasted time, and in an attempt to accomplish more in their life, seek to learn new things while they sleep. This is a classic life hack, but it isn't effective. Called hypnopaedia, this idea was popular in the mid-20th Century, and it continues to pop up, driven by the impulse to be more clever than Mother Nature. If there are serious examples of people truly learning things while asleep, we are not aware of them.
That is not to say that sleep is not connected to learning. Well-rested people learn better and memories are consolidated in NREM sleep. Sleep the night after learning is important and beneficial, and REM sleep can spur creativity.
Is it hubris, the challenge, or a desire to increase productivity that drives otherwise healthy sleepers to try to go beyond normal sleep limitations? It is obvious that most enthusiasts are male and under 40 years of age, usually under 30.. Are stories of geniuses who practice polyphasic sleep driving people to try to mimic them? Do people think they can be like Nikolai Tesla, Thomas Edison, and Leonardo da Vinci - alleged polyphasic sleepers.
Or is it just viewing sleep as wasted time and a desire to make the most of available time that drives people to sleep less.
Deep sleep is the type most adults need more of, and Brian Kerr of the website quantifiedself.com thinks he has worked out ways to increase deep sleep time. He mentions lifting weights, which meshes with what others have found about anaerobic exercise and sleep. He also says eating carbohydrates only late in the day will help, and forcing your body into cold and/or hot temperatures right before bed. The thermal stress, both hot and cold, seems to increase deep sleep time in his experience.
But the quest for better control over sleep continues, driven by hubris maybe, or ambition to conquer nature. The US military services are at the forefront of this quest. They were early adopters of the stimulant modafinil, and were giving amphetamines to pilots in the 1940s. More recently Special Forces units have employed z-drugs to shift their sleep times and make sure their soldiers are well-rested before missions. Military research is trying to find non-pharmaceutical methods to hack the sleep cycle. Already, pilot helmets are fitted with special lights to mimic early morning light and keep them awake. A device that fits over the head called the Somneo mask promises to help induce sleep quickly even when the soldier’s circadian cycle calls for waking. It is hoped the Somneo or similar equipment will help military units squeeze sleep in at the most opportune times during critical missions.
Transcranial direct-current stimulation (tDCS) applies and electric potential across the temples and is approved by the FDA for home treatment of some brain disorders. Promoters hope it will start being used by healthy people to induce slow-wave deep sleep sooner than would normally occur in a night’s sleep. A related technology called transcranial magnetic stimulation is approved for treatment of depression and there are hopes it will be used to enhance sleep quality or shorten sleep times.
None of these are a "cure" for sleep, but some see them as viable ways to significantly shorten daily sleep requirements. Could a permanent shortening of sleep be as revolutionary on society as the birth control pill? Given how much of our lives are spent sleeping and how our schedules work around sleep, it seems that is not an unreasonable comparison.