Background: A nocturnal sleep-onset rapid eye movement period (nSOREMP) is considered diagnostic for narcolepsy type 1 (NT1) if typical cataplexy is also present. The diagnostic value of nSOREMP for narcolepsy type 2 (NT2) is less clear partly because it has not been studied in large groups representing the population attending a sleep centre. We examined the prevalence of nSOREMP and its diagnostic value for narcolepsy in clinical practice.
Methods: We reviewed clinical records and nocturnal polysomnography (nPSG) findings of all people who attended a Dutch sleep-wake centre between 2015 and 2019. The prevalence of nSOREMPs was examined across twelve sleep disorders. Sensitivity, specificity and positive and negative predictive values of nSOREMP for NT1 and NT2 were estimated.
Results: Of 1348 adults (aged ≥18) and 177 children (aged 12-17) included, nSOREMPs were most prevalent in children with NT1 or NT2 (68.3 %) followed by adults with NT1 (47.0 %), NT2 (46.0 %), insufficient sleep syndrome (ISS, 11.4 %), periodic limb movement disorder (7.9 %), chronic insomnia (2.7 %), sleep apnea (2.6 %) and idiopathic hypersomnia (IH, 2.4 %). A nSOREMP was highly specific for NT1 (96 %) and NT2 (93 %) but had limited positive predictive value (NT1: 52.4 % and NT2: 9.7 %) in adults.
Conclusions: A nSOREMP can only be used as a diagnostic for NT1 and NT2 in the presence of other specific hallmarks, such as cataplexy in NT1. Beyond that, it has no diagnostic value in adults as it is also present in other, more prevalent sleep disorders, with the highest occurrence in ISS.
Keywords: Hypersomnolence; Idiopathic hypersomnia; Insufficient sleep; Polysomnography; Sleep deprivation; Sleep-onset REM period.
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