Photo by Pedro Ribeiro Simoes licensed under Flickr Creative CommonsStress. Our jobs. Sick children. There are many reasons why we are sleep deprived. If only we could bank sleep for when we need it.
Turns out we can.
University of Calgary Faculty of Kinesiology researcher Guillaume Millet, PhD, and Pierrick Arnal, PhD, have discovered that "storing sleep" before a period of sleep deprivation improves physical performance and cognitive function.
“We work more and sleep less. It is very common that people in Western populations, especially those in professional fields, are sleeping less than six hours per night,” says Millet. His research was profiled in a brief in American College of Sports Medicine Bulletin.
“And for some of us, there are many occasions when we need to be even more sleep deprived for a short period of time. We wanted to see what would happen if people could sleep more and benefit later.”
Consequences of sleep deprivation are myriad
There are many consequences for not getting enough sleep, from driving performance (falling asleep at the wheel) to obesity, diabetes, and increased risk of other diseases. For athletes and the general population, there is decreased performance, higher rating of perceived exertion during exercise, and a reduced willingness to exercise.
“We are hoping our work will provide a potential strategy to manage the sleep-wake cycle for athletes and others in professions where there is shift work,” says Millet.
Long-distance drivers, health workers, those working in the military or in aviation, and ultramarathon runners could potentially benefit from what the researchers refer to as sleep extension.
The researchers’ subjects were 12 healthy men, young, and good sleepers who slept the same number of hours during the week and on the weekend, suggesting they were not chronically sleep deprived. In the study, the subjects were awake during 38 consecutive hours. They did cognitive tests regularly, as well as a fatigue test where they tried to maintain a given force level for as long as possible.
The subjects performed the same protocol twice; once with their usual amount of sleep and once where they were asked to be in bed for two more hours (for example, going to bed at 9 p.m. rather than 11 p.m.) in the six nights before the 38 hours of sleep deprivation.
Sleep extension shows potential benefits for the chronically sleep deprived
The researchers found that physical performance was improved when the duration of sleep was extended, likely due to the fact the subjects felt the exercise was easier. The researchers also showed the sleep extension period had a beneficial effect on cognitive function and sleep pressure, which is measured by the time elapsed from the start of a daytime nap period to the first signs of sleep, called sleep latency.
“Although this needs to be confirmed in further studies, we believe that the longer the exercise, the more beneficial extra sleep may be—especially in a particular sport competition where sleep deprivation is prevalent, as in ultra-endurance races where sleep can be a limiting factor,” says Millet.
“We also believe that the beneficial effect of sleep extension would be accentuated in people who are chronically sleep deprived. We are looking at conducting a similar study in people with sleep disorders or with a particular sleep schedule, for instance shift work.”
For “normal” sleepers, researchers recommend to:
- Increase the sleep period time to either catch up on your sleep debt or to anticipate a sleepless period. In the current study, this was done by going to bed two hours earlier (for example, 9 p.m. instead of 11 p.m.).
- Have a regular routine of sleep and good sleep hygiene.
- Reduce light exposure in the evening and avoid the use of stimulants for four to six hours before bedtime.
What about caffeine and naps?
Caffeine is the most used psychostimulant in the world (think coffee and energy drinks). A nap is an efficient way to counteract harmful effects of sleep debt, but it is not recommended for people with insomnia since it can be affect the following night's sleep. The nap's duration can be anywhere from five minutes to a complete cycle (90 minutes), yet it is usually recommended to nap for less than 30 minutes or for a full cycle.
A good way to optimize napping and avoid sleep inertia at wake-up is to combine the stimulant effects of caffeine with the recovery effects of the nap. It consists of drinking a coffee immediately before taking a short 20- to 30-minute nap. Since caffeine usually takes 30 minutes to be active at the central nervous system level, you should wake up in good shape.
More about the researchers
Guillaume Y. Millet, PhD, is a professor in the Faculty of Kinesiology at the University of Calgary, where he leads the Neuromuscular Fatigue Laboratory. His general research area investigates the physiological, neurophysiological, and biomechanical factors associated with fatigue, both in extreme exercise (ultra-endurance, hypoxia) and with patients (neuromuscular diseases, cancer). Dr. Guillaume is also an ultramarathon runner.
Pierrick J. Arnal, PhD, completed his academic training at the French Armed Forces Biomedical Research Institute (IRBA) in Paris, France and the University of Lyon-Saint Etienne, France, where his research focused on the preventive countermeasures to limit degradation of cognitive and physical performances and hormonal responses induced by sleep deprivation. He is currently a researcher at Rhythm in Paris and San Francisco. Rhythm is a startup, dedicated to developing technological solutions to improve sleep.