Severe fatigue in narcolepsy with cataplexy

Excessive daytime sleepiness (EDS) is the core symptom of narcolepsy. However, there have been indications that fatigue which should be separated from EDS is also a frequent complaint. We determined the prevalence of severe fatigue in a group of narcolepsy patients and its relation with excessive daytime sleepiness, psychological distress, functional impairment and quality of life. We included 80 patients fulfilling the International Classification of Sleep Disorders (ICSD)-2 diagnostic criteria of narcolepsy with cataplexy. Fatigue was measured using the Checklist Individual Strength (CIS). In addition psychological distress, including symptoms of depression, functional impairment and quality of life, were assessed. Comparisons were made between patients with (CIS-fatigue score = 35) and without severe experienced fatigue. Fifty patients (62.5%) reported severe fatigue. There were no sex or age differences between patients with and without severe fatigue. Both fatigued and non-fatigued patients had the same amount of daytime sleepiness (Epworth Sleepiness Score 14.3 +/- 4.2 versus 13.1 +/- 4.4, P = 0.22), confirming the separation between sleepiness and fatigue. Interestingly, fatigued patients more often used stimulant medication (64% versus 40%, P = 0.02). Severe fatigue was associated with a significantly increased functional impairment, increased depressive symptoms and a lowered general quality of life. In conclusion, a majority of patients with narcolepsy suffer from severe fatigue, which can be distinguished from daytime sleepiness, and results in severe functional impairment.