The Natural History of Health and Symptoms in Narcolepsy: A to-year Longitudinal Study

Abstract

This longitudinal study investigated, over a 10-year period, reported changes in people with narcolepsy (a disorder of excessive daytime sleepiness). The issues of the functional impact of symptoms; stimulant medication status; body mass index, and concomitant illnesses were examined. The study also documented, using retrospective report, environmental factors influencing narcolepsy severity, and reported time of worst symptom severity following narcolepsy onset. In 1991, 127 people with diagnosed narcolepsy and cataplexy completed a wide-ranging questionnaire. In 2001, attempts were made to recontact these participants and 67 were traceable. Of these, 47 people, (18 males, 29 females; mean age 61.76 years, age range 31-86 years) returned a revised questionnaire. The reported impact of excessive daytime sleepiness (EDS) on the ability to carry out day-to-day activities showed minor increases in severity over the 10-year period in this older narcolepsy sample, and this could not be attributed to major changes in medication status. It is argued that the underlying severity of EDS does not increase with time, but rather that the interaction of EDS with the ageing process increases its detrimental impact. Improvements in the functional impact of sleep paralysis, hallucinations and automatic behaviour were reported. There was no evidence that any narcolepsy symptom became substantially worse with time for most people with the disorder. The influence of environmental factors on symptoms was inconsistent within the group. The elevated body mass index, stable over time, suggested that excess weight may be a trait often associated with narcolepsy, possibly linked to hypocretin deficiency.