Miya Pearson
Sleep is a mysterious beast. Despite taking up around a third of our lives, science is still unsure of all the reasons humans need it. However, researchers are beginning to understand that our sleep needs may be influenced by our genes. Scientists have identified a gene mutation that causes people to sleep less than six and a half hours each night without any apparent ill effects. This mutation, found in the ADRB1 gene, is inherited and results in a shortened sleep cycle. It's not the only one—another mutation in the DEC2 gene has also been linked to shorter sleep patterns. Scientists suspect there are several more.
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What You'll Learn
The DEC2 gene mutation
In 2009, Ying-Hui Fu, a neurology professor at the University of California, San Francisco, discovered a mutation in the DEC2 gene. This mutation is responsible for what is known as the "natural short sleep trait". People with this mutation go to bed at a regular time (11 p.m. to midnight) but wake up naturally after just 4 to 6 hours of sleep, feeling well-rested.
The DEC2 gene helps control levels of orexin, a hormone involved in maintaining wakefulness. The sleep disorder narcolepsy is caused by a lack of this hormone. The DEC2 gene mutation releases the brakes on orexin production, resulting in higher levels of this hormone.
Additionally, DEC2 plays a role in regulating circadian rhythms, our natural biological clock. It follows a circadian schedule, rising during the day and falling at night. This helps control the release of hormones and influences behaviours such as eating and sleeping.
The DEC2 mutation has been found to reduce a person's level of alertness in the evening by binding to and inhibiting MyoD1, a gene responsible for turning on orexin production. As the night progresses, DEC2 levels gradually decrease, allowing MyoD1 to stimulate orexin production and promote wakefulness.
The DEC2 mutation is quite rare, but it is not the only gene mutation that can cause natural short sleep. Other mutations, such as the one in the ADRB1 gene, have also been identified as contributing factors to reduced sleep needs.
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ADRB1 gene mutation
The amount of sleep a person needs is influenced by their genetics, with researchers at the University of Pennsylvania finding that up to 80% of an individual's sleep needs could be determined by their genes.
In 2019, scientists at the University of California, San Francisco (UCSF) identified a mutation of the ADRB1 gene in a family that reported sleeping less than six and a half hours each night without feeling any negative effects. This mutation has been identified as the "natural short sleep trait", with mice engineered with the ADRB1 mutation displaying the same brief sleep patterns as humans with the mutation.
The ADRB1 gene codes for the β1-adrenergic receptor, which is found on many cells in the body and responds to hormones that regulate the sleep/wake cycle. The UCSF researchers found that certain brain cells expressed high levels of the β1-adrenergic receptor, and these cells were located in a brain region called the dorsal pons, which is involved in regulating sleep behaviours.
The researchers also found that brain cells with the ADRB1 mutation showed altered activity and electrophysiological properties, making them more easily activated. Mice with the ADRB1 mutation slept almost an hour less each day than normal mice, with about seven minutes less of REM sleep and 53 minutes less of non-REM sleep.
The discovery of the ADRB1 mutation provides an opportunity to develop treatments for people with this genetic mutation, who are at an increased risk of serious health issues such as obesity, diabetes, and heart conditions due to sleep deficits.
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Sleep and genetics research
The study of sleep genetics is a relatively new field, with researchers still asking fundamental questions about the links between sleep and genetics. While we don't yet have all the answers, recent studies have provided some insight and advanced the field of sleep medicine.
NHLBI Study on Sleep Gene Differences
The National Heart, Lung, and Blood Institute (NHLBI) conducted a study on gene differences to explain why some people need more sleep than others. They bred 13 generations of fruit flies with varying sleep durations, and found 126 variations in 80 different genes that could be linked to sleep duration. This provided evidence of a connection between sleep and genetics.
UCSF Study on a Sleep Gene Mutation
In 2019, researchers at the University of California, San Francisco (UCSF) discovered a mutation of the ADRB1 gene in a family who slept less than six and a half hours each night without negative effects. This mutation, known as the "natural short sleep trait," was also found in genetically engineered mice, who displayed similar brief sleep patterns.
University of Pennsylvania on the DEC2 Gene
In 2014, researchers at the University of Pennsylvania identified a mutation of the DEC2 gene as the cause of different sleep patterns in a pair of twin brothers. The DEC2 gene is responsible for turning off the expression of other genes, including the one that keeps us awake. The mutation inhibits the DEC2 gene from carrying out its function.
Sleep Needs and DNA
A study published in Molecular Psychiatry in 2014 involving 47,000 participants suggested that the number of hours a person sleeps may be linked to one of two locations on human DNA. The first region was associated with efficient glucose breakdown and a lower likelihood of developing ADHD, while the second region was linked to an increased risk of schizophrenia and depression.
Consequences of Sleep Deprivation on DNA
Lack of sleep has been found to cause DNA damage, particularly in those who sleep too little each night, such as night-shift workers. This damage can lead to serious physical and mental health complications, including an increased risk of cancer and impaired judgment.
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Sleep and health
Healthy sleep involves not only getting enough hours of sleep but also sleeping at the right time of day and having good quality sleep. Good quality sleep means getting enough of two different phases of sleep: rapid eye movement (REM) sleep and non-REM sleep. REM sleep is the deep sleep in which dreaming occurs. You may not be getting quality sleep if you don't feel rested after sleeping enough, or if you repeatedly wake up during the night.
Sleep is involved in memory consolidation and probably gives cells and tissues a chance to rest, regenerate, and clear out the day's buildup of waste products. A lack of sleep also seems to impair the immune system.
People who are chronically sleep-deprived have a higher risk of diabetes, cancer, and Alzheimer's disease. Sleep deprivation has also been linked to an increased likelihood of serious health issues, including obesity, heart conditions, and depression.
On the other hand, some people are able to function well on just a few hours of sleep each night without experiencing negative health consequences. Researchers have discovered that this ability may be due to a rare mutation in the ADRB1 or DEC2 gene, which increases wakefulness and keeps memory intact.
While the study of sleep genetics is still relatively new, researchers are working to understand how our bodies regulate sleep and how this knowledge can be used to improve sleep health for everyone.
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Sleep and memory
During the NREM stages, the brain sorts through memories from the previous day, filtering out important memories and eliminating other information. These selected memories become more concrete during deep NREM sleep and continue to be processed during REM sleep. Emotional memories are also processed during the REM stage, which can help individuals cope with difficult experiences. Dreaming, which mostly occurs during REM sleep, is when the thalamus of the brain transmits cues from the five senses to the cerebral cortex, which then interprets and processes this information from memories.
Research has shown that memories of certain procedures, like playing a melody on a piano, can improve while sleeping. Memories seem to become more stable during the deep stages of sleep. REM sleep, the most active stage, links together related memories, sometimes in unexpected ways. This is why a full night of sleep may help with problem-solving.
Sleep is also essential for the brain to clean itself. During sleep, the brain has the opportunity to remove waste metabolites, such as beta-amyloid and abnormal tau proteins, which are associated with an increased risk of cognitive disorders like Alzheimer's disease.
Lack of sleep can have detrimental effects on memory. People who don't get enough sleep may experience difficulty remembering things, as the brain doesn't have sufficient time to create new pathways for new information. Sleep deprivation can also lead to other cognitive impairments, such as trouble learning and focusing, reduced decision-making skills, and poor emotional and behavioural control.
Memory consolidation has been found to be stronger in children after a good night's sleep, and excessive sleep can lead to cognitive impairments in both children and adults. Therefore, it is crucial to strive for the optimal amount of nightly sleep, as too little or too much can have negative repercussions on memory and overall cognitive function.
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