Rem Sleep Onset: A Unique Sleep Disorder

Sleep onset REM (rapid eye movement) periods, or SOREMPs, refer to REM sleep that occurs within 15 minutes of falling asleep. SOREMPs are a highly specific indicator of narcolepsy, a sleep disorder characterised by unstable sleep/wake regulation, excessive sleepiness, fragmented nocturnal sleep, and, in some cases, REM sleep intrusion into wakefulness. SOREMPs can also be observed in depressive patients and in people who are sleep-deprived, or who work night shifts.

Sleep onset REM periods (SOREMPs) are REM sleep periods that occur within 15 minutes of falling asleep

Sleep onset REM periods (SOREMPs) are periods of REM (rapid eye movement) sleep that occur within 15 minutes of falling asleep. Typically, REM sleep occurs after 60 to 120 minutes of sleep, but in some cases, it can happen much sooner. SOREMPs can be indicative of narcolepsy, a sleep disorder characterised by unstable sleep/wake regulation, excessive sleepiness, fragmented nocturnal sleep, and, in some cases, REM-sleep intrusion into wakefulness.

The presence of SOREMPs is a highly specific indicator of narcolepsy, but it is not sensitive, meaning that it does not occur in all cases of narcolepsy. In other words, while most people with SOREMPs may have narcolepsy, not all people with narcolepsy will experience SOREMPs. This makes SOREMPs a useful but not definitive diagnostic tool for narcolepsy.

In addition to narcolepsy, SOREMPs may also be observed in people with depression and in healthy individuals under certain conditions. These conditions include non-24-hour sleep/wake schedules, such as shift work, partial sleep deprivation, and physical or psychological stress.

The appearance of SOREMPs is influenced by various factors, including individual characteristics such as being a short sleeper, the circadian rhythm of REM sleep, and body temperature rhythm. The rate of SOREMPs is higher when the latter half of the sleep period, which coincides with the body temperature minimum, is interrupted compared to the first half.

The study of SOREMPs and their relationship to sleep disorders and other factors is ongoing, and further research is needed to fully understand their significance and the underlying mechanisms involved.

SOREMPs are indicative of narcolepsy

Sleep-onset REM periods (SOREMPs) are REM (rapid eye movement) sleep periods that occur within 15 minutes of falling asleep. SOREMPs are indicative of narcolepsy.

Narcolepsy is a sleep disorder characterised by unstable sleep/wake regulation, excessive sleepiness, fragmented nocturnal sleep, and REM-sleep intrusion into wakefulness. It is a rare condition, with a prevalence of between 0.02% and 0.2%.

The presence of SOREMPs is a highly specific indicator of narcolepsy, with a high positive predictive value. However, it is not a sensitive indicator, as patients with narcolepsy often have a normal latency to REM sleep. Nevertheless, the presence of SOREMPs can provide a critical opportunity for practitioners to identify narcolepsy in sleep clinic patients.

The International Classification of Sleep Disorders, Third Edition (ICSD-3) states that a SOREMP during PSG (polysomnography) can count towards one of the two SOREMPs required on the subsequent MSLT (Multiple Sleep Latency Test) for a diagnosis of narcolepsy. The DSM-5 (Diagnostic and Statistical Manual of Mental Disorders, 5th Edition) suggests that a SOREMP during PSG is sufficient to confirm a diagnosis of narcolepsy without requiring an MSLT.

In children and adolescents, the presence of a nocturnal SOREMP is highly suggestive of narcolepsy with cataplexy and provides further evidence of REM sleep dysregulation. The specificity of a nocturnal SOREMP for detecting narcolepsy with cataplexy is high, but the sensitivity is moderate.

In summary, while the presence of SOREMPs is a highly specific indicator of narcolepsy, it is not sufficient on its own for diagnosis. Other clinical symptoms, sleep studies, and diagnostic criteria must also be considered to confirm a diagnosis of narcolepsy.

SOREMPs are highly specific but not sensitive for narcolepsy

Sleep-onset REM (rapid eye movement) periods, or SOREMPs, are REM sleep periods that occur within 15 minutes of falling asleep. SOREMPs are indicative of narcolepsy, a sleep disorder characterised by excessive daytime sleepiness, unstable sleep/wake regulation, and fragmented nocturnal sleep.

SOREMPs are highly specific for narcolepsy, meaning that if a patient experiences SOREMPs, it is highly likely that they have narcolepsy. However, SOREMPs are not sensitive for narcolepsy, meaning that not all people with narcolepsy will experience SOREMPs. This lack of sensitivity may be due to differences in scoring techniques or sample characteristics. For example, a study by Andlauer et al. found a higher sensitivity of 50.6% for SOREMPs in diagnosing narcolepsy, compared to the 6.7% found in the present study. This discrepancy may be due to the fact that the Andlauer et al. study included patients with narcolepsy with cataplexy or documented hypocretin deficiency, while the present study had a majority of cases without cataplexy.

The presence of SOREMPs is a valuable tool in the diagnosis of narcolepsy, as it offers high specificity. However, due to its low sensitivity, SOREMPs should not be relied upon as the sole diagnostic criterion. Other diagnostic tests, such as the Multiple Sleep Latency Test (MSLT) and polysomnography (PSG), are also necessary to confirm a diagnosis of narcolepsy. The MSLT measures the time it takes to fall asleep during the day, while PSG records brain activity, eye movement, and muscle movement during sleep. Combining these tests with the presence or absence of SOREMPs can help clinicians make a more accurate diagnosis of narcolepsy.

SOREMPs are influenced by REM propensity in the circadian rhythm of normal nocturnal sleep

Sleep onset REM periods (SOREMPs) are REM (rapid eye movement) sleep periods that occur within 15 minutes of falling asleep. SOREMPs are indicative of narcolepsy, a sleep disorder characterised by unstable sleep/wake regulation, excessive sleepiness, fragmented nocturnal sleep, and REM-sleep intrusion into wakefulness.

Research has shown that interrupting nocturnal sleep can lead to SOREMPs at the second sleep onset following the interruption. This is more common in short sleepers, who tend to have a higher REM sleep pressure or propensity. The occurrence of SOREMPs reflects the circadian variation of REM propensity in the natural course of nocturnal sleep.

The circadian rhythm of REM sleep is closely connected to body temperature rhythm. The body temperature minimum usually coincides with the latter half of the sleep period, during which REM duration is typically longer due to higher REM propensity. Therefore, interrupting the latter half of sleep leads to a higher likelihood of SOREMPs at the second sleep onset compared to interrupting the first half.

In summary, SOREMPs are influenced by REM propensity, which is affected by the circadian rhythm of REM sleep and the body's temperature rhythm. Interrupting nocturnal sleep, especially during the latter half, can increase the occurrence of SOREMPs due to the higher REM propensity during that time.

SOREMPs are also observed in depressive patients

Sleep-onset REM periods (SOREMPs) are REM (rapid eye movement) sleep periods that occur within 15 minutes of falling asleep. SOREMPs are indicative of narcolepsy and are rarely observed in the general population. However, SOREMPs are also observed in depressive patients.

The presence of SOREMPs in depressive patients was first investigated by Schulz et al. in 1979. They found that during depression, REM sleep latencies are distributed bimodally, with peaks at sleep onset (SOREMPs) and 60 minutes later. In contrast, during remission, the occurrence of SOREMPs is very rare. This suggests that the occurrence of SOREMPs in depressive patients may be caused by a reduced amplitude of the circadian rhythm of the arousal system.

Furthermore, studies have found a high prevalence of depression in patients with narcolepsy. It has been suggested that the chronic and debilitating nature of narcolepsy may contribute to the development of depressive symptoms. However, some research indicates that a shared pathophysiology related to hypocretin deficiency may also play a role. Hypocretin (also known as orexin) deficiency has been linked to both narcolepsy and depression, and it is hypothesized that this deficiency may impede appropriate emotional input processing within the amygdala.

The presence of SOREMPs in depressive patients has important implications for diagnosis and treatment. The occurrence of SOREMPs can be a critical opportunity for practitioners to identify narcolepsy in sleep clinic patients. However, it is important to rule out other sleep disorders and ensure adequate control of sleep timing and duration before conducting sleep testing. Additionally, the presence of depressive symptoms in patients with narcolepsy can further complicate the diagnosis and treatment of this condition. Therefore, comprehensive care for patients with narcolepsy should include surveillance for psychiatric illness and appropriate treatment when necessary.

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