Regarding sleep, normal circadian function allows people to maintain balance rest and wakefulness that allows people to work and maintain alertness during the days activities, and rest at night.Some misconceptions regarding circadian rhythms and sleep commonly mislabel irregular sleep as a circadian rhythm sleep disorder. In order to be diagnosed with CRSD, there must be either a misalignment between the timing of the circadian oscillator and the surrounding environment, or failure in the clock entrainment pathway. Among people with typical circadian clock function, there is variation in chronotypes, or preferred wake and sleep times, of individuals. Although chronotype varies from individual to individual, as determined by rhythmic expression of clock genes, people with typical circadian clock function will be able to entrain to environmental cues. For example, if a person wishes to shift the onset of a biological activity, like waking time, light exposure during the late subjective night or early subjective morning can help advance ones circadian cycle earlier in the day, leading to an earlier wake time. Diagnosis
The International Classification of Sleep Disorders classifies Circadian Rhythm Sleep Disorder as a type of sleep dyssomnia. Although studies suggest that 3% of the adult population has a CRSD, many people are often misdiagnosed with insomnia instead of a CRSD. Of adults diagnosed with sleep disorders, an estimated 10% have a CRSD and of adolescents with sleep disorders, an estimated 16% may have a CRSD.
Patients are similarly asked to self-report their sleep habits with a week-long sleep diary to document when they go to bed, when they wake up, etc. to supplement the actigraphy data. Collecting this data allows sleep professionals to carefully document and measure patients sleep habits and confirm patterns described in their sleep history.Other additional ways to classify the nature of a patients sleep and biological clock are the morningness-eveningness questionnaire (MEQ) and the Munich ChronoType Questionnaire, both of which have fairly strong correlations with accurately reporting phase advanced or delayed sleep. Questionnaires like the Pittsburgh Sleep Quality Index (PSQI) and the Insomnia Severity Index (ISI) help gauge the severity of sleep disruption. Specifically, these questionnaires can help the professional assess the patients problems with sleep latency, undesired early-morning wakefulness, and problems with falling or staying asleep.Tayside childrens sleep questionnaire is a ten-item questionnaire for sleep disorders in children aged between one and five years old. Types
Currently, the International Classification of Sleep Disorders (ICSD-3) lists 6 disorders under the category of circadian rhythm sleep disorders.CRSDs can be categorized into two groups based on their underlying mechanisms: The first category is composed of disorders where the endogenous oscillator has been altered, known as intrinsic type disorders. The second category consists of disorders in which the external environment and the endogenous circadian clock are misaligned, called extrinsic type CRSDs. Intrinsic
Delayed sleep phase disorder (DSPD): Individuals who have been diagnosed with delayed sleep phase disorder have sleep-wake times which are delayed when compared to normal functioning individuals.