Retrospective cohort study of hypersomnias of central origin from two Australian tertiary sleep disorders services.

Background: Hypersomnias of central origin (HOCO) are diverse in origin and symptomatology and remain poorly described in an Australian population. We hypothesised that the rate of human leukocyte antigen (HLA) DQB1*0602 positivity in the Australian cohort would be comparable to international registries.

Aims: The current study aims to evaluate epidemiological and clinical characteristics of Australian patients with HOCO, including prevalence of HLA DQB1*0602 positivity, the most specific HLA marker associated with narcolepsy.

Methods: This is a retrospective study. Patients ≥ 16 years of age presenting with symptoms of hypersomnolence who attended one of two Australian sleep centres (New South Wales and Queensland) in the preceding 24 months and had undergone both HLA serology and multiple sleep latency tests (MSLTs) were included. Main outcome measures included demographics, HLA DQB1*0602 positivity, MSLT, and clinical parameters (presence of auxiliary narcolepsy symptoms, laboratory tests, relevant prescribed medications).

Results: Eighty-eight patients were included. HLA DQB1*0602 positivity was highest in those with type 1 narcolepsy (NT1) (95.7%) and lowest in those without a classifiable disorder (9.1%). Mean sleep latency was lowest and number of sleep-onset rapid eye movement periods (SOREMPs) highest in the NT1 group. Comorbid disorders, particularly depression and overweight/obesity, were prevalent in all cohorts. Across all diagnostic groups, dexamphetamine was the most commonly prescribed agent for excessive daytime sleepiness.

Conclusions: Patients with HOCO assessed in two specialised Australian clinics demonstrate comparable clinical characteristics to other published cohorts internationally; however, available pharmacological agents in Australia do not reflect international standards of care.