Bright light therapy may improve sleep in cancer patients
Systematic exposure to bright white light (BWL) in the morning may help improve sleep in fatigued cancer survivors, suggests a pilot study.
“Sleep disturbances are most commonly treated with medications but many cancer patients are reluctant to add more medications to their list,” according to the researchers.
“Systematic light exposure [sLE] using bright white light is a low-cost and easily disseminated intervention that offers a feasible and potentially effective [non-pharmacological] alternative to improve sleep in cancer survivors,” said lead author Dr Lisa Wu of Northwestern University Feinberg School of Medicine in Chicago, Illinois, US.
The researchers randomized 44 cancer survivors (mean age 53.6 years, 75 percent females) who had been screened for cancer-related fatigue to receive either BWL or dim red light (DRL) from a light box for 30 minutes daily every morning for 4 weeks. Sleep was assessed using wrist actigraphy as well as the Pittsburgh Sleep Quality Index. [J Clin Sleep Med 2017;pii:jc-17-00369]
At the end of intervention, sleep efficiency ─ defined as the percentage of time in bed when the person is sleeping ─ was significantly improved to the clinically normal range (mean, 86.06 percent) in the BWL group, while that of the DRL group remained in the impaired range (mean, 79.35 percent).
The improvement with BWL was sustained even 3 weeks after intervention (mean, 85.77 percent) compared with the impaired sleep efficiency with DRL (mean, 80.88 percent).
There were significant time × treatment group interaction effects with BWL vs DRL (p=0.003), with a large effect size (partial η2, 0.28).
Effect sizes for other measures such as total sleep time, sleep quality, and wake after sleep onset (WASO) ranged from medium to large in favour of BWL, suggesting greater benefits with morning BWL over DRL on these outcomes, although the improvements (time × treatment group interactions) were not statistically significant.
“Given that time in bed remained consistent across time for both groups, and that there were marginal time × treatment effects favouring the BWL group with respect to total sleep time and WASO, it appears that the favourable improvements to sleep efficiency in the BWL group were not due to reductions in time in bed,” noted Wu and co-authors.
“Light is a powerful synchronizer of the human circadian system because of its effects on the brain via a non-image forming photoreceptor system that is distinct from rods and cones, with the potential to improve sleep via its effects on circadian rhythms,” they explained.
As the study was a secondary analysis on a small sample, the researchers acknowledged that the findings were not adjusted for multiple comparisons, and hence, served more to inform future studies than to provide a definitive conclusion.
“This study demonstrates the promise of sLE as a treatment not only for cancer-related fatigue but also for cancer-related sleep problems that affect a large number of cancer survivors,” said Wu and co-authors, who suggested larger-scale studies be done to assess the efficacy of sLE for treating sleep disturbances.