Interrater and intrarater reliability in multiple sleep latency test.

Multiple sleep latency test (MSLT) remains the golden standard for the clinical diagnosis and management of excessive daytime sleepiness. However, there was limited data on the reliability measurement of MSLT. Forty-four (M/F ratio: 26/18, mean age of 43.4 +/- 13.9 years) subjects of an ongoing family study of narcolepsy underwent a standard polysomnogram and MSLT. Three trained staff of various level of experiences independently and blindly scored each nap (n = 219). To test for intrarater reliability, 100 naps (n = 20 subjects) were re-scored half a year later. The interrater reliability for the mean sleep latency of 5 naps, sleep latency, and rapid eye movement (REM) sleep latency of individual nap, presence and numbers of sleep onset REM periods varied from the range of 0.668 to 0.964. The mean interrater reliability for the clinical diagnosis of narcolepsy was 0.883 (range, 0.824-0.938), whereas it was 0.750 (range, 0.674-0.858) for the diagnosis of narcolepsy spectrum disorder (shortened mean sleep latency and/or the presence of sleep onset REM periods) and 0.796 (range, 0.697-0.846) for normal cases. The intrarater reliability for the sleep latency and sleep onset REM periods varied from the range of 0.625 to 0.991. Our study demonstrated excellent inter- and intrarater reliability in scoring the sleep latency and sleep onset REM periods of MSLT. They also had excellent agreement on the diagnosis of narcolepsy and an "excellent to good" agreement on the diagnosis of narcolepsy spectrum disorder and normal cases. Our study lent further support that MSLT was an objective measurement with high inter- and intrarater reliability across various sleep disorders and healthy controls among different sleep centers.

Narcolepsy in Southern Chinese patients: clinical characteristics, HLA typing and seasonality of birth.

OBJECTIVE: To report clinical characteristics, human leukocyte antigen (HLA) typing and seasonality of birth of a series of 54 Southern Chinese patients suffering from narcolepsy. METHODS: All subjects underwent detailed medical and psychiatric interviews and a standardised nocturnal polysomnogram followed by a daytime Multiple Sleep Latency Test. Each subject also completed a set of sleep questionnaires. HLA typing was performed in 91% of subjects. RESULTS: A total of 78% and 22% of patients were diagnosed with suffering from cataplectic and non-cataplectic narcolepsy, respectively. The majority (n = 47, 87%) of patients were referred to our sleep clinic for excessive daytime sleepiness (EDS). The cataplectic narcolepsy differed from non-cataplectic narcolepsy by having more rapid eye movement (REM)-related clinical symptoms (more sleep paralysis and sleep-related hallucination) and sleep disturbances (shorter REM latency), as well as tighter association with HLA DQB1*0602. A bi-modal peak pattern was observed at 11 and 39 years old. A similar bi-modal pattern also occurred for EDS and cataplexy. Excess winter births were observed for this series of patients. 81% of patients with cataplectic narcolepsy were DQB1*0602-positive. There were no differences between early- and late-onset cases in the association with positive DQB1*0602 (71.4% vs 60%). Narcolepsy had prominent pernicious effects on various social, academic, family and mental aspects in our patients. CONCLUSIONS: In our Southern Chinese narcolepsy series, bi-modal peak pattern of age of onset, excess winter birth and tight association of HLA DQB1*0602 with cataplectic narcolepsy were found.

The familial risk and HLA susceptibility among narcolepsy patients in Hong Kong Chinese.

STUDY OBJECTIVES: To explore the familial aggregation and HLA susceptibility of narcolepsy in Hong Kong Chinese by objective sleep measurements and HLA typing. DESIGN: Case control design PARTICIPANTS: Twelve narcoleptic probands, 34 first-degree relatives, and 30 healthy controls. INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: Each subject underwent a standardized nocturnal polysomnogram (PSG), followed by a daytime multiple sleep latency test (MSLT). HLA typing was performed for all subjects. One relative (2.9%) was diagnosed as suffering from narcolepsy with cataplexy. Nearly 30% of the relatives fulfilled the criteria of narcolepsy spectrum disorder (shortened mean sleep latency [MSL] and/or the presence of sleep onset REM periods [SOREMPs]). When using the population data for comparison, the relative risk of narcolepsy in first-degree relatives was 85.3. The odds ratio of narcolepsy spectrum disorder in first-degree relatives was 5.8 (95% CI: 1.2 - 29.3) when compared to healthy controls. There existed 6 multiplex families, in which all 10 relatives with narcolepsy spectrum disorders, including all 3 relatives with multiple SOREMPs, were positive for HLA DQB1*0602. CONCLUSIONS: Our study demonstrated a definitive familial aggregation of narcolepsy, narcolepsy spectrum disorders, and possibly cataplexy in Hong Kong Chinese. This familial aggregation supported an inherited basis for narcolepsy spectrum. The tight co-segregation of HLA DQB1*0602 and narcolepsy spectrum disorders might suggest that HLA typing, especially DQB1*0602, at least partly confer the familial risk of narcolepsy. In addition, our study suggested that the subjective questionnaire measurements including Ullanlinna Narcolepsy Scale and Epworth Sleepiness Scale were unable to detect the presence of narcolepsy spectrum disorders among the relatives. A stringent objective measurement-based design for family studies is suggested for future study. Further studies are indicated for the determination of the mode and molecular level of narcolepsy transmission.

Comparing MSLT and ESS in the measurement of excessive daytime sleepiness in obstructive sleep apnoea syndrome.

OBJECTIVE: The objective of this study is to compare the use of Multiple Sleep Latency Test (MSLT) and Epworth Sleepiness Scale (ESS) in measuring excessive daytime sleepiness (EDS) in patients with different severity of obstructive sleep apnoea syndrome (OSAS). METHOD: Two hundred ninety-six consecutive OSAS patients, with their EDS measured by a Chinese version of ESS and a five-nap MSLT, and their severity of OSAS (determined by respiratory disturbance index) by a nocturnal polysomnogram, were classified into mild (RDI 5-15/h, n=59), moderate (RDI 15-30/h, n=71) and severe (RDI >30/h, n=166) groups, respectively. Their ESS, MSLT and other sleep parameters were compared. RESULTS: The severe group had significantly shorter mean sleep latency (MSL=6.26+/-4.90 min) than the moderate (8.26+/-4.57 min) and mild groups had (8.07+/-4.37 min). There was no significant difference in their ESS scores. CONCLUSION: MSLT is better than ESS in the measurement of EDS in relation to the severity of OSAS in clinical patients.

Delayed neuropsychiatric impairment after carbon monoxide poisoning from burning charcoal.

Poisoning by carbon monoxide from burning charcoal has become one of the popular and lethal ways of attempting suicide in Hong Kong. Survivors of the carbon monoxide poisoning often face acute and delayed adverse problems in both their physical and mental health. We report two cases of delayed onset neuropsychiatric complications caused by carbon monoxide poisoning from burning charcoal. These symptoms were characterised by a latent period, followed by an abrupt and profound deterioration in the neurocognitive function with a seemingly reversible course. The literature is reviewed regarding the aetiology, pathophysiology, and management of this condition. Regular monitoring of their neurocognitive function and forewarning of this potential complication to the survivors of carbon monoxide poisoning and their families should be essential.

Gender differences in insomnia--a study in the Hong Kong Chinese population.

OBJECTIVE: To study the epidemiology of insomnia in the adult Chinese population in Hong Kong and to examine the potential gender-related demographic and lifestyle factors in insomnia. METHODS: A population study via random telephone survey with a structured questionnaire was carried out for noninstitutionalized Chinese adults aged 18-65 by trained lay interviewers. The questionnaire included demographic data, sleep habits and problems, insomnia symptoms and lifestyle questions. RESULTS: A total of 9851 subjects (46.4% male; 53.6% female) were included in the final analysis. The overall prevalence of Hong Kong Chinese as suffering from insomnia during the preceding month (with a frequency of sleep disturbance of at least three times per week) was 11.9% (95% CI 11.2-12.6), including difficulty in initiating sleep (DIS) (4.5%; 95% CI 4.1-5.0), difficulty in maintaining sleep (DMS) (6.9%; 95% CI 6.4-7.5) and early morning awakening (EMA) (4.0%; 95% CI 3.6-4.4). Females were about 1.6 times at higher risk for insomnia than males. The prevalence of insomnia was also shown to increase with age. Multivariate analysis showed that unemployment, lower economic status, alcohol consumption, regular medication and psychiatric disturbance were all associated with higher risks of insomnia in both sexes. Furthermore, lower education level and being retired was associated with a higher risk of insomnia in males, but being a housewife, divorced/widowed, and complaining of a nocturnal noisy environment were associated with a higher risk of insomnia in females. Among all these factors, psychiatric disturbance was the most influential risk factor for insomnia in both sexes. The reasons for gender differences of insomnia may include their differences in the prevalence of psychiatric morbidities, symptom endorsement, gonadal steroids, sociocultural factors and coping strategies. CONCLUSIONS: Overall, 11.9% of the Hong Kong Chinese adult population complained of frequent insomnia in the preceding month. There was a higher prevalence of insomnia in females. Although there were common risk factors for insomnia in both sexes, there existed gender-specific risk factors.