title: The relationship between fatigue and light exposure during chemotherapy.
abstract: BACKGROUND
  Fatigue is one of the most common and distressing complaints among cancer patients, not only during radiation and chemotherapy, but also for months to years after the completion of treatment. Fatigue interferes with patients' daily lives, reduces their quality of life, and is often a significant reason why patients discontinue treatment. We hypothesized that some of the fatigue may be related to disrupted circadian rhythms and low light exposure. The main objective of this study therefore was to investigate the association between fatigue and light exposure among patients with breast cancer.
  
  
  METHODS
  As part of a larger, ongoing prospective study on fatigue, sleep, and circadian rhythms in patients with breast cancer, an analysis of 63 women newly diagnosed with stage I-IIIA breast cancer and scheduled to receive four cycles of adjuvant or neoadjuvant anthracycline-based chemotherapy was conducted. Data were collected before and during weeks 1, 2, and 3 of cycle 1 and cycle 4. Fatigue was assessed using the Short Form of Multidimensional Fatigue Symptom Inventory. Light exposure was recorded with a wrist actigraph.
  
  
  RESULTS
  There were significant correlations between fatigue levels and light exposure (r=-0.28 to -0.45) within both cycle 1 and cycle 4, such that higher levels of fatigue were associated with less light exposure. There were also significant correlations between changes in light exposure and changes in fatigue within the first 2 weeks of each cycle (r=-0.28 to -0.52).
  
  
  CONCLUSIONS
  Increased fatigue was significantly correlated with decreased light exposure among patients with breast cancer. Although the cause and effect of exacerbated fatigue and decreased light exposure cannot be confirmed by the current study, and lower light exposure may just in part be due to the fatigued patients spending less time outdoors in bright light, two hypotheses are proposed about the mechanisms by which light may alleviate the fatigue of patients with breast cancer. These results suggest the need for prospective intervention studies of light therapy for breast-cancer-related fatigue.
authors.affiliation: Department of Psychiatry, University of California San Diego, San Diego, CA 92161, USA.
authors.forename: Lianqi
authors.initials: L
authors.lastname: Liu
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Marler
authors.forename: Barbara A
authors.initials: BA
authors.lastname: Parker
authors.forename: Vicky
authors.initials: V
authors.lastname: Jones
authors.forename: Sherella
authors.initials: S
authors.lastname: Johnson
authors.forename: Mairav
authors.initials: M
authors.lastname: Cohen-Zion
authors.forename: Lavinia
authors.initials: L
authors.lastname: Fiorentino
authors.forename: Georgia Robins
authors.initials: GR
authors.lastname: Sadler
authors.forename: Sonia
authors.initials: S
authors.lastname: Ancoli-Israel
mesh_terms: D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000188:drug therapy; D002940:Circadian Rhythm / Q000187:drug effects; D004358:Drug Therapy; D005221:Fatigue / Q000139:chemically induced* / Q000209:etiology; D005260:Female; D006801:Humans; D008029:Lighting; D008875:Middle Aged; D011446:Prospective Studies; D014481:United States