How sleep is related to fatigue

Abstract

Objectives. It is evident that sleep patterns have direct effects on fatigue. However, the multidimensionality of fatigue may imply that complex patterns of relationships exist between fatigue and sleep characteristics. We aimed to study the correlations between fatigue and quantitative and qualitative sleep measurements, while taking into consideration depression and somatization which are known to affect both sleep and fatigue. We predicted that sleep quality, unattained by the effects of somatization and depression, would affect perceived fatigue more than the quantitative characteristics of sleep. Design. Employing a cross-sectional design, hypotheses were addressed using multiple hierarchical regression analyses according to established methods. Methods. Data were gathered from a targeted, randomly selected adult sample (N = 278) by means of subjective sleep reports, a mental health inventory, somatization inventory, several fatigue questionnaires and a demographic questionnaire. Results. Fatigue was significantly predicted by depression scores, somatization levels and subjective sleep quality, but not quantitative sleep characteristics such as sleep latency, nocturnal awakenings and early morning arousals. Depression levels were positively and significantly related to all aspects of fatigue except physical fatigue and fatigue that responds to rest and sleep. Physical fatigue was correlated with somatization, but not depression. Conclusions. The data further our understanding of the multifaceted nature of human fatigue and underline the greater importance of perceived sleep quality, compared to other sleep characteristics, in predicting fatigue.