Light Therapy May Treat Excessive Daytime Sleepiness in Parkinson’s Disease

Light therapy may reduce excessive daytime sleepiness and improve sleep quality in patients with Parkinson’s disease, according to trial results published in the April issue of JAMA Neurology. The treatment modality is well tolerated, widely available, and “relatively easy to prescribe and incorporate into a clinical practice,” said Aleksandar Videnovic, MD, a neurologist at Massachusetts General Hospital in Boston, and colleagues.

Aleksandar Videnovic, MD

Impaired sleep and alertness are common nonmotor manifestations of Parkinson’s disease with limited treatment options. Patients’ sleep disturbances have been attributed to Parkinson’s disease symptoms, adverse medication effects, and neurodegeneration of central sleep regulatory areas. Altered circadian rhythms also may play a role. Supplemental exposure to bright light improves sleep quality and daytime vigilance in healthy older people and patients with dementia, but the treatment modality has not been studied systematically in patients with Parkinson’s disease, the researchers said.

One-Hour Treatment Intervals

To determine the safety and efficacy of light therapy on excessive daytime sleepiness associated with Parkinson’s disease, Dr. Videnovic and colleagues conducted a randomized, placebo-controlled trial.

They enrolled 31 patients with Parkinson’s disease and excessive daytime sleepiness (ie, an Epworth Sleepiness Scale score of 12 or greater). Patients were receiving stable dopaminergic therapy and did not have cognitive impairment or a primary sleep disorder. Investigators randomized participants 1:1 to receive bright light therapy (10,000 lux) or a control condition of dim-red light therapy (less than 300 lux). After a two-week baseline phase, participants received light therapy in one-hour intervals twice daily—in the morning (between 9 am and 11 am) and in the afternoon (between 5 pm and 7 pm)—for 14 days. The primary outcome measure was change in Epworth Sleepiness Scale score from baseline. During the study, each patient wore an actigraphy monitor and completed a daily sleep log and various other assessments.

During treatment, a light box was placed 86.4 cm away from the patient. Participants were instructed to sit quietly and not nap. They could listen to music or audiobooks.

The 31 patients (18 females) had an average age of about 63 (range, 32 to 77) and an average disease duration of about six years. Among patients who received bright light therapy, mean Epworth Sleepiness Scale score significantly improved from 15.81 at baseline to 11.19 post intervention. The improvement was significantly greater than that for patients in the control group, who had a mean Epworth Sleepiness Scale score of 15.47 at baseline and 13.67 post intervention.

Improvements in sleep quality, latency, and fragmentation were significantly greater in the bright light therapy group than in the control group. In both treatment arms, light therapy was associated with increased daily physical activity, as assessed by actigraphy, and reduced disease severity, as assessed by the Unified Parkinson’s Disease Rating Scale. Light therapy was not associated with significant changes in depression, anxiety, or quality of life.

In the active treatment group, one patient reported headache, and another patient reported sleepiness. One participant in the control group reported itchy eyes. The adverse events resolved spontaneously, and adherence to the study protocol was excellent, the researchers said.

Although improvement in the control arm may have been due to the placebo effect, it is also possible that “anchoring the light therapy to a strict twice-daily regimen provided means for structuring daily activities, which itself may be an interesting possible mechanism underlying the beneficial effects of … light therapy,” Dr. Videnovic and colleagues said. Future studies should address the optimal treatment parameters for light therapy in Parkinson’s disease, they added.

Whether light therapy produces direct alerting effects, influences the circadian system, or works through another mechanism is not clear. A limitation of the study was that light levels were not measured throughout the day, so patients in the control group could have received more light from other sources overall, compared with patients in the active treatment group, the investigators noted.

Chronobiologic Interventions

The study shows that chronobiologic interventions “can be used therapeutically in patients with Parkinson’s disease” and “introduce a new concept into the much-studied phenomenon of disturbed sleep and wakefulness in Parkinson’s disease,” said Birgit Högl, MD, of the Department of Neurology at the Medical University of Innsbruck in Austria, in an accompanying editorial. Although the study of chronobiology is complex, certain aspects of chronobiology can be “integrated into routine medical practice and improve outcomes for patients,” Dr. Högl said.

—Jake Remaly

Suggested Reading

Högl B. Circadian rhythms and chronotherapeutics-Underappreciated approach to improving sleep and wakefulness in Parkinson disease. JAMA Neurol. 2017;74(4):387-388.

Videnovic A, Klerman EB, Wang W, et al. Timed light therapy for sleep and daytime sleepiness associated with Parkinson disease: A randomized clinical trial. JAMA Neurol. 2017;74(4):411-418.