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Title: Light Therapy for Post-Treatment Cancer-Related Fatigue: An Investigation of Impact on Psychological Outcomes and Biological Mechanisms
Author: Johnson, Jillian
Advisor: Campbell, Tavis
Keywords: Oncology;Psychology;Psychology--Clinical;Psychology--Physiological
Abstract: OBJECTIVE: To investigate the impact of a one-month light therapy intervention on symptoms of fatigue, psychological outcomes, and diurnal cortisol rhythms in cancer survivors with clinical fatigue. METHODS: Adult cancer survivors who met diagnostic criteria for cancer-related fatigue were eligible and randomized to receive either bright white light (BWL) or an active comparator (dim red light; DRL). Participants used the device for 30 minutes upon waking for 4 weeks. Baseline and post-intervention assessments of fatigue, mood disturbance, depression, sleep quality, and quality of life were obtained. Participants also provided four saliva samples per day over a period of 3 days both before and after the intervention. Linear mixed-model (LMM) analysis with random slopes and intercepts were conducted on the primary outcome of fatigue, and generalized estimating equations were employed to investigate the secondary psychological outcomes. Cortisol slopes, total cortisol output (area under the curve), and cortisol output at four sampling times were examined for time, group, and interaction effects using LMM analyses. RESULTS: Eighty-one participants were randomized to either BWL (n=42) or DRL (n=39). The light therapy intervention was acceptable as evidenced by high adherence rates and low dropout (2.5%). Overall, participants in the BWL condition displayed greater improvements in symptoms of fatigue than those in the DRL condition (d=.30). Both groups showed improvements on symptoms of mood disturbance, depression, sleep quality, and quality of life over time. A subsample of participants (n=77) were included in the cortisol analyses. Cortisol slope and total cortisol output were unchanged after the intervention, but an increase in output was observed in both groups at the post-intervention noon sample, as well as decreased output at the post-intervention 5pm sample in the BWL condition. CONCLUSION: Early morning exposure to bright white light resulted in improvements in symptoms of fatigue in cancer survivors with clinical fatigue. These findings, along with those of previous research of light therapy in cancer patients and survivors, support the use of light therapy for cancer-related symptoms. Furthermore, light therapy has the potential to impact the diurnal release of cortisol, though further research into the associations with symptoms of fatigue are required.
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