Objectives: The aim of this study was to investigate the influence of age on the manifestation of narcolepsy symptoms and cognitive difficulties in patients with narcolepsy.
Methods: A total of 321 participants were included in the study: 157 were patients with narcolepsy from two Sleep Disorders Clinics and 164 were control participants. Narcoleptic patients were evaluated and diagnosed at the Sleep Disorders Clinic. All participants were interviewed by telephone using the Sleep-EVAL System. The interview comprised, among else, a detailed evaluation of narcolepsy symptoms and of cognitive difficulties.
Results: The first manifestation of the disease appeared early in life for most narcoleptic patients: 54.1% had their first symptom before the age of 20 years. Daytime sleepiness was the first symptom to appear in 65.5% of cases. In narcoleptics 60 years or older, cataplexy was more likely to be the first symptom to appear (47.4%) compared with other narcoleptic patients (21.4%; P<.05). Reported cognitive difficulties (attention-concentration, praxis, delay recall, orientation for persons, temporal orientation, and prospective memory) were higher in narcoleptic patients compared with the controls. The severity of daytime sleepiness and the presence of a major depressive disorder partly explained the cognitive difficulties. However, attention-concentration deficits and difficulties in prospective memory remained significant. Age was unrelated to cognitive difficulties in narcoleptics patients.
Conclusions: The first manifestation of narcolepsy appears early in life. Reported cognitive difficulties are important in narcoleptic patients and are only partly explained by age, severity of daytime sleepiness, and major depressive disorder.