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September 06, 2019 – Wakefulness varies largely among human individuals. Barring individuals suffering from diseases such as narcolepsy that may heavily dictate an individual’s daily sleep and wakefulness pattern, there are individuals in the general population who needs a lot of sleep and there are those who seemingly never sleep and still feel fit and good at performing their daily tasks.
How come? Only about 10 years ago sleep researchers discovered that people who had inherited a particular mutation (i.e., hDEC2-P385R) in a transcriptional repressor gene called DEC2 averaged only 6.25 hours of sleep per night, while study participants lacking the mutation averaged 8.06 hours. At the time, this finding provided the first evidence that natural short sleep has, at least in some cases, a genetic basis. But this mutation is rather rare in the general population, so while it helped explain some natural short sleepers, it couldn’t possibly account for all of them. Moreover, experts in sleep research were thinking all along that there had to be other, as yet undiscovered genetic causes of short sleep.
In fact, after a 10-year long search, scientists have now identified a second ‘short sleep’ gene. A new study just published in the Journal Neuron as of August 28, 2919 describes a breakthrough in sleep research when the researchers identified a family that included three successive generations of natural short sleepers, none of whom harbored the DEC2 mutation identified earlier as the first ‘short sleep gene’. The researchers used gene sequencing and a technique known as linkage analysis, which helps scientists pinpoint the exact chromosomal location of mutations associated with a particular trait, to comb through the family’s genome. Their efforts uncovered a single-letter mutation in the β1-adrenergic receptor gene ADRB1 that, like the mutation in the DEC2, was associated with natural short sleep.
“Before we identified the first short-sleep gene, people really weren’t thinking about sleep duration in genetic terms,” said Ying-Hui Fu, Ph.D., professor of neurology and a member of the UCSF Weill Institute for Neurosciences. Dr. Fu led the research teams that discovered the first and now the second short sleep genes. According to Dr. Fu, many scientists once thought that certain sleep behaviors couldn’t be studied genetically. “Sleep can be difficult to study using the tools of human genetics because people use alarms, coffee and pills to alter their natural sleep cycles,” she said. These sleep disruptors, the thinking went, made it difficult for researchers to distinguish between people who naturally sleep for less than six hours and those who do so only with the aid of an artificial stimulant. One of the breakthroughs came now when the researchers identified a family that included three successive generations of natural short sleepers, none of whom harbored the DEC2 mutation.
Sleep remains complicated, however. Though they sleep less, natural short sleepers don’t suffer any of the adverse health effects associated with sleep deprivation. Today, most people are chronically sleep deprived. If you need eight to nine hours, but only sleep seven, you’re sleep deprived. This has well-known, long-term health consequences. You’re more likely to suffer from cardiovascular disease, cancer, dementia, metabolic problems and a weakened immune system. This is not the case for natural short sleepers. They even seem actuallyto benefit from this quirk of their biology. Thus, seemingly short sleepers tend to be more optimistic, more energetic and better multitaskers. They also have a higher pain threshold, don’t suffer from jet lag and some researchers believe they may even live longer. Though the exact reasons for these benefits remain unknown.
An interesting question to pose in this context would be if the natural short sleepers are also natural early risers (i.e., early birds) or not. And how does the short time of sleep fit into their circadian rhythm and their underlying genetic chronotyp? What combination of genes or genetic variants thereof make up the true behaviour of an individual when it comes to natural sleep characteristics?
See here a short sequence on a good nights sleep (the chronotypes of it):