Altered Circadian Rhythms and Cancer-Related Fatigue Outcomes

Fatigue is one of the most frequent and distressing complaints reported by patients with cancer. Describing relationships among disrupted circadian rhythms and cancer-related fatigue is important to the design and testing of interventions that target specific underlying etiology of fatigue. The purpose of this article is to review the literature on whether evidence exists to support the notion that disrupted circadian rhythms provide a mechanism of cancer-related fatigue. Searches were conducted from January 1950 to January 2010, to locate pertinent articles using 4 electronic databases: PubMed, MEDLINE, CINAHL, and Scopus. Results identified 42 quantitative research studies, which were then retrieved. After reviewing the articles, 15 were selected as meeting the established criteria of the study and were critiqued. Statistical approaches varied across studies, which may influence generalizability of results. Although commonalities across studies did emerge, there was a lack of consistency in variables studied, and most studies did not identify a theoretical framework. More research needs to be conducted using consistent types and characteristics of disrupted circadian rhythms in relation to fatigue, including temporal relationships between circadian rhythms, fatigue, and cancer.