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Familial sleep traits

Genetic Basis of Familial Sleep Traits: – Louis Ptáček and colleagues discovered evidence of a human familial circadian rhythm variant in the 1990s. – Phyllis […]

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Genetic Basis of Familial Sleep Traits:
– Louis Ptáček and colleagues discovered evidence of a human familial circadian rhythm variant in the 1990s.
– Phyllis Zee and Joseph Takahashi conducted genetic analysis on Familial Advanced Sleep Phase (FASP).
– Mutations in genes like DEC2, ADRB1, CRY1, CRY2, PER2, PER3 influence sleep disorders.
– Familial Advanced Sleep Phase (FASP) and Familial Delayed Sleep Phase (FDSP) have genetic components.
– Ying-Hui Fu and Ptáček discovered the first short-sleep gene in 2009.
– Continued research into the human genome is crucial for understanding heritable sleep traits.

Clinical Aspects of Familial Sleep Disorders:
– Advanced Sleep Phase Syndrome (ASPS) and Delayed Sleep Phase Syndrome (DSPS) were identified in the late 20th century.
– Individuals with FASP have earlier chronotypes and a free-running period of about 22 hours.
– Individuals with FDSP typically have a delayed sleep onset and offset, with a free-running period longer than 24 hours.
– Fatal Familial Insomnia (FFI) causes trouble sleeping, dementia, and death, with a 6-36 month prognosis.
– Treatments for FASP and FDSP involve light therapy, chronotherapy, and melatonin.

Heritable Sleep Traits and Genetic Studies:
– Twin studies and genetic research have been conducted to understand sleep quality, duration, and behavior.
– Various genes like CRY1, CRY2, PER2, DEC2, and ADRB1 are linked to different familial sleep traits.
– Studies have explored the impact of mutations on Alzheimer pathology, stress response, and other health conditions.
– Research has identified mutations affecting sleep/wake behaviors and sleep duration in individuals with specific sleep traits.
– Recent studies have linked mutations in specific genes to natural short sleep traits and their potential impact on Alzheimer pathology.

Circadian Rhythm Sleep Disorders and Therapeutics:
– Circadian rhythms are crucial for sleep timing and are influenced by genetics.
– Melatonin, light therapy, and other treatments are used for circadian rhythm sleep disorders.
– Fatal Familial Insomnia (FFI) is a severe disorder with no definitive cure, often requiring palliative care.
– Studies have delved into the clinical features, molecular genetics, and therapeutic approaches for circadian rhythm sleep disorders.
– Disorders of sleep and circadian rhythms have been studied in the context of neurogenetics.

Epigenetic Factors and Recent Discoveries in Sleep Research:
– Dec1, Dec2, and other genes regulate the mammalian molecular clock and sleep behavior.
– Recent studies have identified mutations affecting sleep traits and their potential impact on neurodegenerative diseases.
– Research has explored the role of epigenetics in regulating sleep duration and chronobiological disorders.
– Meta-analyses and systematic reviews have been conducted to understand the heritability estimates related to sleep quality and duration.
– Studies have highlighted rare mutations, genetic links to natural short sleep traits, and the protective effects of elite sleeper genes against neurodegenerative diseases.

Familial sleep traits (Wikipedia)

Familial sleep traits are heritable variations in sleep patterns, resulting in abnormal sleep-wake times and/or abnormal sleep length.

Circadian rhythms are coordinated physiological and biological changes that oscillate on an approximately 24-hour cycle. Disruptions to these rhythms in humans may affect the duration, onset, and/or quality of sleep during this cycle, resulting in familial sleep traits. These traits are not necessarily syndromes because they do not always cause distress among individuals. Instead of being disorders, familial sleep traits are variations in an individual's biological tendencies of sleep-wake times, and are only considered syndromes if affected individuals complain about life interference, in which case they may fall under the category of Circadian Rhythm Sleep Disorders (CRSD) that affect sleep timing and circadian rhythms. Some of these circadian disorders include Advanced Sleep Phase Disorder (ASPD) and Delayed Sleep Phase Disorder (DSPD). Familial sleep traits are more specific than CRSD because they are heritable and involve a wide range of Mendelian genes. Evidence has shown that genes significantly influence sleep schedules in mammals, including humans, and account for one-third of the variation in sleep quality and duration. Studies in human monozygotic twins have provided evidence that genetic factors affect "normal" sleep patterns as well, meaning ones where no individual has been diagnosed with an altered phenotypic sleep trait.

Sleep timing is controlled by the circadian clock, which can entrain to environmental stimuli (usually a light-dark cycle) and is regulated by a transcription-translation feedback loop (TTFL). In humans, there are multiple genes involved in this molecular biological clock, which when mutated may result in sleep disorders such as Familial Advanced Sleep Phase (FASP), Familial Delayed Sleep Phase (FDSP), and Familial Natural Short Sleep (FNSS). Some mutations in Mendelian genes that are involved in the TTFL have been identified as the causes of these sleep traits, including PER2, PER3, CRY2, CRY1. Other Mendelian genes that are not known to play a core role in the TTFL but are involved in FNSS include DEC2 and ADRB1.

With some familial sleep traits, there may be a shift in an individual's chronotype, which describes the time of sleep-wake behaviors that result from circadian rhythms. Chronotype may shift depending on multiple factors including gender and age. Individuals with FASP have earlier chronotypes and individuals with FDSP have later chronotypes compared to a conventional sleep period which runs from approximately 10pm to 7am. Individuals may meet the criteria for FASP or FDSP if they have Advanced Sleep Phase or Delayed Sleep Phase and at least one first degree relative with the trait. Researchers have examined the human prevalence of FASP to be 0.33-0.5% by including individuals who have a sleep onset at approximately 8:30pm and offset at 5:30am. FDSP, which includes individuals who have a delayed sleep onset and offset, has an unknown human prevalence and may vary based on location, definition, and age.

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