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This article is part of our October 2021 special issue. Download the full issue here.
Relation
Wu HS, Davis JE, Chen L. Bright light shows promise in improving sleep, depression, and quality of life in women with breast cancer during chemotherapy: results of a pilot study.Chronobiol Int. 2021;38(5):694-704.
Study objective
To learn whether bright light home treatment tailored to participants' circadian phase preference would affect their sleep, fatigue, daytime sleepiness, depression, and quality of life during chemotherapy
Draft
Controlled pilot study
Participant
A total of 18 women with newly diagnosed stage I to III breast cancer participated in this study, and 16 completed it. Their ages ranged from 29 to 68 years, with the majority being white/Caucasian and college educated. Most were treated for stage II breast cancer. Individuals were excluded if they had a history of seasonal affective or psychiatric disorders, were taking photosensitizers or sleeping pills, or had other malignancies or cancer treatments, along with other exclusions.
intervention
Investigators assigned participants to the experimental condition (bright blue-green light of 12,000 lux) or the control condition (dim red light of 5 lux). Participants received light therapy for 30 minutes via a light visor each day at adjusted times depending on their circadian chronotype. Evening types began light exposure within 30 minutes of waking, and morning types had light exposure between 7 and 8 p.m. Light therapy was administered for 21 consecutive days after the second cycle of chemotherapy.
Study parameters assessed
The investigators collected a variety of both subjective and objective measures. They collected baseline data before participants began their second cycle of chemotherapy, and they conducted final data collection on the day of the third chemotherapy treatment.
Subjective measures included the Patient-Reported Outcomes Measurement Information System (PROMIS), which measures fatigue. Subjective sleep quality was assessed with the Pittsburgh Sleep Quality Index (PSQI) and daytime sleepiness with the Epworth Sleepiness Scale (ESS). The Patient Health Questionnaire (PHQ-9) measures depression. Quality of life was measured with the European Organization for Research and Treatment of Cancer-Quality of Life Questionnaire (EORTC QLQ-C30).
Sleep was assessed objectively using ambulatory polysomnography (PSG).
Primary outcome measures
Investigators calculated the relative change from baseline to posttest data for both groups. In addition, between-group analysis was performed using 2-sample t-tests.
Key insights
The experimental group had significant sleep improvements both subjectively and objectively. Subjectively, falling asleep took less time – only 10 minutes in the experimental group versus 20 minutes in the control group (P=0.045). This was confirmed by the PSG data (14 vs. 63 minutes) of the 7 participants who used the PSG at home.
Polysomnography showed longer sleep time of 467 minutes and higher sleep efficiency of 74% in those who received bright light, versus 315 minutes of total sleep and only 58% sleep efficiency in the control group. While these differences did not reach statistical significance, the trends over the short time period of the study are worth noting here.
There was a 30% relative decrease in depression among those in the bright light group and a 24% relative increase among controls, but these also failed to reach statistical significance.
Quality of life was less negatively affected by chemotherapy in the intervention group, with symptom intensity (as reported in the EORTC questionnaire results) increasing by 33% versus 166% in the control group. Fatigue did not change with light therapy despite apparently better sleep.
Practice implications
Given that fatigue and sleep disturbances affect a large proportion of breast cancer patients, this approach, if validated, could have significant impact on a large population of women. Light therapy is relatively inexpensive and easy to perform and has few, if any, negative side effects. Light therapy is currently used to treat circadian rhythm sleep-wake disorders and seasonal affective disorder. Maybe we can add this list to complement chemotherapy?
The sleep improvements seen with light therapy in this study were quite amazing, with over 2 hours more sleep per night and 16% higher sleep efficiency in the experimental group. For the individual cancer patient (and other patients), improved sleep can lead to better daytime functioning. Adults are recommended to sleep between 7 and 9 hours each night.1The light therapy group achieved this goal after 21 days of treatment.
This study was unique in its use of participants' chronotype to determine the time of day for the intervention.
Poor sleep quality or duration leads to multiple impairments from performance to mood to health measures. Notably, sleep stage percentages remained abnormal in both the control and experimental groups, with 78% stage 2 sleep (increased from the normal value of about 50%) and reduced percentages of REM and stage 3 sleep. It may be that fatigue levels did not change in part because REM and stage 3 sleep were reduced from normal.
This study was unique in its use of participants' chronotype to determine the time of day for the intervention. Our chronotype is an inherent characteristic set by the suprachiasmatic nucleus in the hypothalamus and reinforced by the clock genes in every cell.2With light therapy (and easily with melatonin supplementation) the circadian phase can be manipulated. However, once light therapy is stopped, the person returns to their natural phase preference. Therefore, a third examination of cancer patients after the treatment period would be helpful to determine whether changes recorded during active light therapy persist (and if so, for how long) or whether light therapy needs to be continued.
It is interesting that the treatment group was not separated into the 2 treatment conditions: light in the morning versus light at night. Light at these different times of day has significantly different effects on our circadian system.3Light in the evening suppresses evening melatonin production and shifts the circadian rhythm backwards, while light in the morning has the opposite effect, shifting the circadian rhythm earlier and increasing the next night's nocturnal melatonin peak. The researchers intentionally adjusted the timing of the light therapy to put participants in a more neutral circadian phase. This furthers the previous work of Dr. Sonia Ancoli-Israel,4which showed that bright morning light prevented both quality of life and fatigue from decreasing during chemotherapy.
Additionally, people have historically been exposed to bright light in the morning but not in the evening. Our circadian system has evolved in accordance with this pattern in the color and brightness of light in the natural environment. It is known that artificial light at night can have negative effects on human health, including the risk of cancer. The International Agency for Research on Cancer concluded that night shift is a probable carcinogen (Group 2A carcinogen).5Other research reports have found that women who work night shifts have an increased risk of breast cancer.6For these reasons, we in the clinic are cautious about administering light therapy during a patient's circadian night.
In future studies with more participants, it would be interesting to see the morning and evening treatment groups separately. Additionally, the control group's ambient light conditions in their homes and lifestyles were not mentioned, so it is unknown how much light they received during the intervention times. The control group may have been in bright light (or blue light) conditions in their home environment.
This pilot study provides hope that light therapy, a relatively simple and inexpensive treatment, may improve sleep and quality of life in women receiving chemotherapy for breast cancer. Stay tuned to see how this approach develops.