Light Therapy May Improve Circadian Rhythms in AYA Cancer Survivors

Sunlight – bright white light, in particular – sets the stage for individual’s sleep/awake patterns, and studies have shown that sleep quality is key in achieving and maintaining optimal health. However, cloudy/rainy days and environments can disrupt access to bright white light and, therefore, have an effect on sleep.

Recent research tested the efficacy and feasibility of bright light therapy on adolescent cancer survivors. Oncology Nursing News spoke with study author Valerie E. Rogers, PhD, RN, CPNP, on the benefit of light therapy for cancer survivors.

Oncology Nursing News: Can you briefly explain your study, and why it was important to conduct?

In this study we pilot tested an intervention to administer bright light therapy (sometimes called bright white light, or BWL) to a group of adolescents who had completed their treatment for cancer of any type within the past 5 years and were off all of their medications. The aim of the study was to develop a method for adolescents to self-administer the BWL intervention, while still being able to monitor their use of the treatment and potential side effects.

BWL is an intervention specific to improving circadian timing, or how well a person’s circadian rhythm matches up with the earth’s light/dark (AKA day/night) cycle. Nearly all of our biological and psychosocial functions have a circadian rhythm to them (e.g. melatonin levels are low during the day and high at night, cortisol and physical activity levels are high during the day and low at night…). We are at our healthiest, and feel our best, when these rhythms match the light/dark cycle, e.g. high mental and physical activity during the day and quiet sleep during the night.

This study was important because there is a growing body of evidence that cancer and its treatment disturb sleep and circadian rhythms. These disturbances can persist for months, years or may even be permanent (the latter has been found in survivors of both adult and pediatric bone marrow transplant). As both healthy sleep and “robust” or healthy circadian rhythms are integral to our health, we are concerned about the health effects of long-term sleep/circadian rhythm disturbances when combined with the late effects of cancer and its treatment.

If we can intervene early to restore healthy circadian rhythms in children who have completed cancer treatment, we may be able to prevent long-term health problems associated with circadian dysregulation , that also overlap late effects of cancer and its treatment, such as diabetes, cardiovascular disease, mental health problems, cancer and others. But, given the high rate of noncompliance with any type of treatment, we tried to find a way to make this intervention convenient and easy to carry out, in the home, by adolescents themselves.

Most studies of BWL have been conducted in adults. We need more pediatric studies.

How does bright white light work?

Every day we are exposed to environmental cues, or “zeitgebers” that help us reset our circadian timing. The most potent one is sunlight. Sunlight (especially light in the blue light range) enters the eyes and stimulates receptors on the retina. This signal travels up the optic pathway to the brain ultimately shuts down melatonin production, which has a strong arousing effect. Light boxes, which are commercially available devices for administering bright light (and screen out harmful UV light), are just a substitute for sunlight, and have the same effect. Morning light, in particular, helps to reset our circadian rhythms if they have drifted to a later clock time (e.g. adolescents tend to go to bed later and later, and wake up later and later, developing what is called a delayed sleep/circadian phase in relationship to sunrise/sunset).

Why might someone need an artificial intervention, as opposed to going by the natural patterns of sunrise/sunset?

Natural sunlight is the best source of light for our circadian health. In fact, it is so good, that the amount of blue light contained in sunlight is actually highest in the mornings, when the effect of blue light on our circadian timing is strongest, and is lowest in the evening when we are gearing down to go to sleep. In contrast, the amount of blue light in artificial light is constant, so can be damaging to our sleep with evening exposure.

Morning BWL can be used as a proxy for morning sunlight during the winter or on cloudy/rainy days when our exposure to sunlight is limited. It can also be helpful if a person is unable to get outside to experience sunlight, such as if they are infirm or chronically fatigued, or have work/school obligations that limit their time for going outside in the mornings. When given a choice, however, sunlight is always best.

How do sleep issues/circadian rhythm disturbances affect health?

Our sleep/wake pattern is one of our circadian rhythms, so I like to think in terms of disturbed circadian rhythms as the cause of long-term sleep problems—they are highly intertwined.

Some of the longer-term health issues associated with short sleep duration and poor-quality sleep in children include suboptimal neurodevelopmental outcomes related to cognition, behavior and academic achievement in children, mental health issues such as depression, obesity, fatigue, and decreased quality of life. Adults, in addition to these, are at risk for cardiovascular disease and metabolic syndrome.

Most of the studies of circadian rhythms has been in adults, particularly those with cancer, but there’s a growing body of research in children now. Together, disturbance of circadian activity rhythms (such as we measured using actigraphy in this study) in adult or pediatric cancer patients has been associated with greater fatigue, poorer quality of life, impaired immune function, lower responsiveness to chemotherapy, earlier relapse and higher risk of death compared to patients with robust (healthy) circadian activity rhythms.

Of note, exposure of adults to working the night shift has been identifies as a carcinogen due to exposure to light at night, which (as mentioned before) stops production of melatonin at a time when our bodies should be recuperating in sleep. Melatonin, as it turns out, is a potent antioxidant with anti-cancer properties, so its absence may allow cancers to gain a foothold in long-term night shift workers.

What are next steps in this line of research, and what unanswered questions remain?

This was a very small study. We’d like to use what we learned from this study to modify this intervention and administer it to a larger sample. We’d like to carry out this study in the hospital setting, where sleep/circadian disturbances often first develop due to noise, light at night, side effects of chemotherapy (e.g. pain, nausea/vomiting, fever…), changes from the child’s normal sleep/wake schedule, etc. In particular, we’re interested in the effect of BWL on children with central nervous system tumors, as these children have the most difficulty over time with sleep and circadian rhythms due to disease-related damage to the hypothalamic-pituitary axis from surgery and irradiation.