Nighttime sleep and daytime functioning (sleepiness and fatigue) in well-defined chronic rheumatic diseases.

Wake/sleep complaints are very common in the rheumatic diseases, and include: insomnia, non-restorative sleep, frequent awakenings, daytime fatigue and excessive daytime sleepiness. Imprecise use of terminology has confused 'sleep dissatisfaction' (i.e. 'non-restorative sleep') with specific sleep disorders (i.e. 'insomnia' or 'sleep fragmentation') and 'fatigue' with 'daytime sleepiness'. This review examines current concepts from the literature of disparate disciplines pertaining to the complaint of poor sleep and daytime fatigue in patients with rheumatic disorders. The ability to monitor multiple physiologic parameters during sleep (polysomnography) has led to a greater understanding of normal and abnormal phenomena which occur during sleep, and has resulted in the identification of a variety of sleep disorders which have specific therapeutic implications. Actigraphy allows the prolonged monitoring of wake/sleep patterns, and the multiple sleep latency test permits the determination of physiologic sleepiness during the daytime. These techniques enable identification of objective sleep disorders in those whose complaint is subjective sleep dissatisfaction, and permit differentiation between the easily confused complaints of excessive daytime sleepiness and fatigue. The abnormal sleep/wake symptoms in patients with rheumatic diseases may not simply be a 'non-specific' or systemic effect of the disease. Some patients may have a specific sleep disorder (either independent from, or due to, the underlying rheumatic condition) which should be diagnosed and treated specifically. Conversely, subjective 'sleep dissatisfaction' does not necessarily imply an underlying sleep disorder. The primary intent of this review is to encourage systematic, objective study of sleep and daytime function in these common, often disabling conditions.