Familial aggregation of narcolepsy

ObjectivesTo determine the familial aggregation of narcolepsy from perspectives of clinical symptomatology, polysomnographic data, and human leukocyte antigen (HLA) typing.MethodsThis was a Family study at the University-affiliated hospital. The participants were narcolepsy probands and their first degree relatives, and, also, age and sex matched unrelated healthy controls. Interventions were not applicable.Measurements and resultsAll study subjects underwent structured interviews, overnight polysomnography followed by a multiple sleep latency test (MSLT), and HLA typing. Altogether, 33 probands and 81 first degree relatives (response rate 65%) were recruited. Among the relatives, 12.3% were diagnosed with narcolepsy and 39.5% had narcolepsy spectrum as defined by unexplained abnormal MSLT (shortened MSL and SOREMP) results. The relative risk of narcolepsy in first degree relatives was 361.8. Familial aggregation of narcolepsy symptoms, excessive daytime sleepiness, HLA status, abnormal MSLT, and nocturnal polysomnographic findings were observed.ConclusionsThe familial risk of narcolepsy among first degree relatives is much higher than previously reported. There exists a spectrum of narcolepsy features among relatives, ranging from full clinical tetrads to asymptomatic abnormal MSLT findings.