Systematic Light Exposure Improves Cancer-Related Fatigue


While previous studies showed bright white light therapy could prevent cancer-related fatigue, researchers also found it improves poor sleep efficiency among a variety of tumor types.

Bright light therapy may be an easy-to-use and inexpensive solution for patients and survivors to address their cancer-related fatigue, according to study results published in the Journal of Clinical Sleep Medicine.

Systematic light exposure, which uses morning bright light therapy, has improved sleep among people with other disorders, including depression, sleep, seasonal affective disorder and circadian rest-wake activity. “Systematic light exposure intervention is less burdensome than other non‐pharmacologic interventions for sleep disturbance such as cognitive behavioral therapy and/or exercise,” lead author Lisa M. Wu, Ph.D., said in an interview with CURE.

“Systematic light exposure using bright white light offers patients a low cost and easily disseminable intervention that offers a feasible and potentially effective alternative to improve sleep in cancer survivors,” added Wu, assistant professor in the department of medical social sciences at Feinberg School of Medicine at Northwestern University.

Meanwhile, sleep disturbances — which occur in approximately 23 to 44 percent of survivors, even years after cancer treatment – are most commonly treated with medications, a method most patients are apprehensive about because of the amount of medications they are already prescribed.

A recent pilot showed that 30-minute bright white light exposure in the morning either prevented or reduced fatigue among women with breast cancer.

So, how exactly does this work? All through synchronizing individuals’ biological circadian systems. “Light is received in the retina of the eye. That information travels down the optic nerve into the part of the brain called the suprachiasmatic nucleus that is the home of our biological clock,” explained Wu. “Light therefore has the potential to improve sleep via its effects on circadian rhythms. From an evolutionary perspective, the synchronization of our biological rhythms to the earth's cycles of light and darkness is essential for health.”

To determine whether systematic light exposure helped a mixed group of patients and survivors, the researchers randomized 44 survivors screened for cancer-related fatigue to receive either bright white light therapy or dim light conditioning.

Survivors were instructed to use a light box each morning for 30 minutes for four weeks. In total, 37 participants completed assessments prior to light treatment, two weeks in to the intervention, during the last week of intervention, and three weeks after the intervention.

More than half of participants suffered from poor sleep efficiency, or how much time people spend in bed is actually spent sleeping. After a month of treatment, 86 percent of those exposed to bright white light reported normal sleep efficiency, while 79 percent of those who underwent dim light conditioning experienced poor sleep efficiency.

In addition, the researchers found that bright white light was associated with medium to large improvements in sleep quality, total sleep time and wake time.

After patients stopped using bright white light therapy, three-week assessments showed that sleep quality improvements had disappeared, and patients no longer fared better than those who had undergone dim light conditioning.

“The take-home message is that exposure to bright white light using a broad-spectrum lamp may be helpful for fatigued cancer patients to improve their sleep,” Wu said.

However, if patients and survivors do not have access to these lamps, the outdoors is an alternative solution. “One great way to get that morning outdoor light is to take a walk as physical exercise also helps strengthen circadian rhythms and also helps improve sleep,” Wu added. “If patients cannot go outside so easily, then they can sit by the window to get as much bright light exposure as possible.”

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