Narcolepsy in Singapore: is it an elusive disease?

The aims of the study were to determine the demographic, clinical, and polysomnographic characteristics of narcolepsy, and to address the difficulties in diagnosing narcolepsy and cataplexy, which is a cardinal symptom. We also ventured to investigate the differences between narcolepsy with and without cataplexy.

Data were collected retrospectively from patients diagnosed with narcolepsy at the Sleep Disorder Unit of Singapore General Hospital over 5 years. Each patient had had a detailed clinical evaluation and overnight polysomnography (PSG) followed by a multiple sleep latency test (MSLT).

A total of 28 cases were studied. Males made up 85.7% of the total and females, 14.3%. The mean age was 30.9 years. All had excessive daytime sleepiness. Other manifestations were cataplexy (48.1%), sleep paralysis (51.9%), hypnogogic hallucinations (84%), disturbed night sleep (29.2%), automatisms (17.4%) and catnaps (95.8%). The mean duration of symptoms was 7.24 years. In the MSLT, the mean values for mean sleep latency and number of sleep onset rapid eye movement (REM) periods (SOREMP) were 4.3 minutes and 2.7, respectively. Narcolepsy was associated with obstructive sleep apnoea and periodic limb movement disorder (35.7%). All the variables were compared between those who had narcolepsy with cataplexy and without cataplexy. The duration of presenting complaint, REM latency, respiratory disturbance index, number of SOREMPs and the presence of sleep paralysis were significantly different in the 2 groups.

Narcolepsy predominantly affects young males. Concurrence of other sleep disorders is not uncommon. Some differences are evident between those who have narcolepsy with and without cataplexy.