“Without sleep you can’t form or maintain the pathways in your brain that let you learn and create new memories, and it’s harder to concentrate and respond quickly.”
So says a 2017 brochure Understanding Sleep, produced by US-based National Institute of Neurological Disorders and Stroke, which also suggests that sleep is “as essential to survival as food and water”.
Yet despite sleep’s ubiquity and documented importance in our lives, the very same brochure adds that “its biological purpose remains a mystery”.
It’s certainly a mystery of sorts. In 2004, a British paper reporting on a study of 2000 adults noted that sleep problems and sleep restriction “are popular topics of discussion, but few representative data are available”.
The following year, an article in the inaugural issue of the Journal of Clinical Sleep Medicine acknowledged that “sleep medicine has only recently been recognised as a specialty of medicine”, adding that it “has evolved over the past 25 years based on the convergence of major developments in the science of sleep and circadian rhythms (chronobiology)”.
In 1951, the Journal says, Nathaniel Kleitman, a professor of physiology at the University of Chicago, with the assistance of his graduate student, Eugene Aserinsky, studied eye movements during sleep.
Their work “culminated in a seminal paper in 1953 in which a new sleep state, REM sleep, was described and a correlation with dreaming hypothesised”.
The Journal goes on to explain how, in 1957, William Dement and Kleitman “described the human sleep cycle of NREM sleep stages of increasing depth followed by periods of REM sleep, with the cycles repeating through the night… This understanding of the electrophysiologic substrate of human sleep has been the basis for the vast literature on sleep that has accumulated over the ensuing half century.”
When Kleitman died in California on 13 August 1999, aged 104, a University of Chicago obituary described him as “the world’s first scholar to concentrate entirely on sleep” and “universally recognised as the father of sleep research”.
It says that before him, “few scientists had systematically investigated the intricacies of sleep, which had previously been dismissed as a state of quiescence”.
“After Kleitman and colleagues demonstrated in the 1950s that sleep was a dynamic and varied process, there was an explosion of interest in sleep, in sleep research and, subsequently, in the treatment of sleep disorders.”
Kleitman was born on 26 April 1895 in Kishinev, part of the Russian empire, to a Jewish family that was forced to flee to Palestine. He moved to the US, arriving in New York 1915, and by 1923 had earned a PhD from the University of Chicago’s department of physiology.
The Guardian newspaper says his book Sleep and Wakefulness, first published in 1939, is “regarded as the supreme work on the subject and the foundation for modern studies”.
In his studies of sleep cycles, it says, Kleitman devised several experiments, including one in 1938 in which he and an assistant tried to adapt to a 28-hour day by living in a cave at a constant temperature of 12 degrees Celsius and no natural light.
He also “dispelled” the “myth” that babies needed 20 to 22 hours of sleep a day, finding that 15 hours was normal.
Kleitman also performed studies that were less benign, The Guardian says, including sleep deprivation experiments in the 1950s, “many on soldiers, and once stayed awake himself for 180 hours. ‘It gets to the point where someone would confess anything just to be allowed to sleep,’ he said”.
“Long periods without sleep were a form of torture, he argued, and so it proved.”