Light therapy for insomnia symptoms in fatigued cancer survivors: a secondary analysis of a randomized controlled trial

Abstract

Abstract Background: Cancer-related fatigue (CRF) and insomnia are highly comorbid. This association implies that treatment aimed at improving one may also simultaneously target the other. This secondary analysis examined whether severity of insomnia affects sleep outcomes in response to a light therapy intervention in cancer survivors with CRF. Methods: This 4-week trial recruited cancer survivors who met ICD-10 criteria for CRF. Participants were randomized to receive bright white light (BWL) or dim red light (DRL). Light devices were used daily for 30 minutes over 28 days. Participants completed the Insomnia Severity Index (ISI) at baseline, weeks 2 and 4, and the Pittsburgh Sleep Quality Index, daily sleep diaries and actigraphy at baseline and week 4. ISI scores 0 to 14 represent no/mild symptoms and scores 15+ correspond to moderate-to-severe (clinically significant) insomnia symptoms. Results: Of the 81 participants (BWL: n = 42; DRL: n = 39), 49% had ISI scores ≥15 at baseline. There was a significant group-by-time interaction for insomnia severity (F[2, 75.55] = 4.15, P = .020) and sleep quality (F [1, 39.25] = 7.66, P = .009), favoring the BWL condition for those individuals with no or mild insomnia symptoms. In the moderate-to-severe group, there were time effects for insomnia severity and sleep quality, diary measured wake after sleep onset and sleep efficiency, and actigraphy measured wake after sleep onset and sleep efficiency; however, participants remained in the clinical range for insomnia symptoms on the ISI and poor sleep quality on the PSQI. Effect sizes were larger, regardless of intervention condition, in participants with moderate-to-severe insomnia symptoms. Conclusions: The severity of insomnia symptoms may impact sleep outcomes in response to a light therapy intervention in cancer survivors with clinical levels of fatigue, but light therapy alone does not appear to be adequate to produce clinically meaningful change in sleep outcomes. Trial registration number: Clinicaltrials.gov identifier NCT01780623.