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Narcolepsy in Hong Kong Chinese--a preliminary experience
1Department of Psychiatry, Prince of Wales Hospital, Chinese University of Hong Kong, Shatin.
Background:
Narcolepsy is a sleep disorder of unknown aetiology. Despite the widely reported strong association with HLA DR2 among different ethnic groups and their varying prevalence rates, there has never been any series of laboratory documented narcolepsy in Chinese.
Aims:
To report the preliminary experience with Chinese narcoleptic patients and their HLA typing.
Methods:
The records of 342 patients who presented to our sleep laboratory for various sleep problems from 1986 to 1992 were examined. Both clinical and polysomnographic data were analysed. The criteria for a diagnosis of narcolepsy is based on shortened mean sleep latency of less than 5 minutes and presence of rapid eye movement (REM) sleep in two or more of the five 20-minute naps during multiple sleep latency test (MSLT).
Results:
There were five narcoleptic patients documented resulting in an overall laboratory prevalence of 1.5% or 2.3% of patients presenting with hypersomnia. All patients were HLA DR2 positive.
Conclusion:
There is 100% association with HLA DR2 in Hong Kong Chinese narcoleptic patients. Based on the laboratory prevalence, the prevalence rate of narcolepsy among Hong Kong Chinese population is estimated to be within the range of four in 10,000 to one in 100,000.