A validity study of Ullanlinna Narcolepsy Scale in Hong Kong Chinese Y.K. Wing*, R.H.Y. Li, C.K.W. Ho, S.Y.Y. Fong, L.Y. Chow, T. Leung Sleep Assessment Unit, Department of Psychiatry, Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China Received 20 December 1999; accepted 16 July 2000 Abstract Objective: To validate the Chinese version of Ullanlinna Narcolepsy Scale (CUNS). Methods: A total of 234 subjects [163 male (69.7%) and 71 female (30.3%)] including 17 patients with narcolepsy, 21 normal controls and 196 patients with various sleep and psychiatric disorders were studied. The diagnoses of these patients were independently ascertained with sleep laboratory confirmation whenever indicated. All the subjects were inter- viewed through the telephone by a trained lay interviewer who was blind to the diagnosis. The questionnaire included demographic information, sleep habits and CUNS. Results: Narcoleptic patients had a significantly higher CUNS score (18.6  4.7; 95% confidence interval (CI) 16.2 ± 21.0) and differentiated well from all the other groups ( F 6,227 = 28.4, P < 0.001). The CUNS has a satisfactory internal consistency with Cronbach's alpha of 0.75. The principal component analysis with varimax rotation revealed two factors, namely sleepiness and cataplexy factors, which accounted for 45.5% of the total variance. The best cut-off point for the CUNS scale was found to be at 13/14 with high specificity (93.5%), sensitivity (94.1%), negative predictive value (NPV, 99.5%) and modest positive predictive value (PPV, 53.3%). The AUC of receiver operating characteristic (ROC) analysis was 0.97 (95% CI 0.95 ± 0.99). Conclusions: The CUNS was validated with satisfactory psychometric properties. The cross-cultural validation of UNS scale suggested that it could be used across the ethnic groups. D 2000 Elsevier Science Inc. All rights reserved. Keywords: Narcolepsy; CUNS questionnaire; Chinese; Cross-cultural; Validity Introduction Sleep disorders are common but under-recognized and under-treated. Excessive daytime sleepiness (EDS), in particular, is a frequent clinical problem and as many as 5% of general population might be suffering from it [16,17]. The causes of EDS are numerous ranging from the more frequent sleep deprivation, sleep ± wake schedule disturbance, drug/alcohol effects and sleep-related breath- ing disorders to relatively rarer but perhaps more dis- abling narcolepsy. Characterized by EDS, cataplexy, nocturnal sleep disturbance and other REM sleep-related phenomenon such as sleep paralysis and hypnagogic hallucination, clinically, narcolepsy is a lifelong crippling sleep disorder with conspicuous physical and psychosocial complications [2,6,7,15]. Recent research suggested that narcolepsy has more marked academic and occupational difficulties, negative socioeconomic impact and crippling effect on daily life than other chronic medical disorders such as epilepsy [6,7]. Although the exact etiology is unknown, both genetic and possibly ethnic and environmental factors are believed to play an important part [2,11]. It has been estimated that the prevalence rate of narcolepsy in general population varies from 0.59% in Japanese to 0.00023% in Israel Jews [11,18,25,26]. One of the major reasons for such nearly 2500-fold difference in the prevalence rate was clearly related to the differences in the methodology and studying population, but possible ethnic predisposition cannot be excluded [18]. Similar data on Chinese narcolepsy has been even more limited. Based on our clinical and laboratory data, the estimated rate of narcolepsy in Hong Kong * Corresponding author. Sleep Assessment Unit, Department of Psychiatry, Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China. Tel.: +852-263-23634/47; fax: +852-263-77884. E-mail address: ykwing@cuhk.edu.hk (Y.K. Wing). Journal of Psychosomatic Research 49 (2000) 355 ± 361 0022-3999/00/$ ± see front matter D 2000 Elsevier Science Inc. All rights reserved. PII:S0022-3999(00)00179-3