The average American sleeps an hour less each night than they did 40 years ago. But if you think that catching up on sleep at the weekend will make up for the sleep you didn't get during the week, dream on.
Researchers at Northwestern University in Chicago have found that repeated sleep loss or interruption quickly damages our ability to catch up on lost sleep.
While the body compensates for occasional sleep loss by sleeping both longer and more deeply the following night, it seems unable to repeat the same trick when sleep deprivation is chronic.
In a study published in the Proceedings of the National Academy of Sciences, rats that had been kept awake for 20 hours per day over five days seldom made up for the sleep they had lost even when given three full days to sleep as much as they wanted.
"We now know that chronic lack of sleep has an effect on how an animal sleeps," said Professor Fred W. Turek, lead author of the study.
"The animals are getting by on less sleep but they do not try and catch up. The ability to compensate for lost sleep is itself lost, which is damaging both physically and mentally," he added
The study is the first to show that repeated partial sleep loss negatively affects an animal's ability to compensate for lost sleep and that the body responds differently to chronic sleep loss than it does to acute sleep loss.
The findings also support what other scientists have discovered in recent experimental studies in humans. Chronic partial sleep loss of even two to three hours per night has a noticeable effect on the body, leading to impairments in cognitive performance, as well as cardiovascular, immune and endocrine functions.
Particularly worrying is the fact that sleep-restricted people often don't feel tired even though their performance on tasks has markedly declined.
With barely more than a quarter of Americans getting the recommended eight hours of sleep each night and almost one in six only getting five hours during the working week, the implications of the research are considerable.
Research carried out for the not-for-profit Better Sleep Council (BSC) has estimated that U.S. businesses are losing an estimated $150 billion annually in absenteeism and lost productivity due to sleep deprivation, with around a third of Americans reporting that sleep deprivation impairs their quality and accuracy of their work, harms their judgment and affects memory of important details.
In some circumstances, such symptoms could be fatal. In the UK, a BBC investigation revealed growing concerns that fatigue among airline pilots is leading to potentially dangerous incidents. Eight out of 10 pilots told a survey by the British Airline Pilot's Association that their performance had been affected by fatigue.
In one incident, a fatigued pilot nearly stalled an aircraft in mid–air shortly after take off.
As the Better Sleep Council's Dr. Bert Jacobson pointed out, the idea that we can accomplish more if we spend less time sleeping is nonsense.
"Limited sleep can affect every aspect of your life, including job performance. In fact, sleep deprivation impacts your level of alertness, your productivity and your ability to socially interact with colleagues."