Light therapy significantly reduced excessive daytime sleepiness, improved sleep quality, decreased overnight awakenings, shortened sleep latency, enhanced daytime alertness and activity level, and improved motor symptoms in patients with Parkinson’s disease, according to a report published online Feb. 20 in JAMA Neurology.

The noninvasive, nonpharmacologic treatment was well tolerated, and patient adherence was excellent in a small, multicenter, randomized controlled trial. Light therapy is widely available as a treatment for several sleep and psychiatric disorders and is “relatively easy to prescribe and incorporate into a clinical practice,” said Aleksandar Videnovic, MD, of the department of neurology at Massachusetts General Hospital and the division of sleep medicine at Harvard Medical School, both in Boston, and his associates.

Sleep disturbances are among the most common manifestations of Parkinson’s disease (PD), and traditionally they have been attributed to PD symptoms, adverse effects of PD medications, and neurodegeneration of central sleep regulatory areas. Accumulating evidence, however, suggests that PD also directly disrupts the circadian system. A few exploratory studies have documented that supplemental exposure to bright light improved depression, bradykinesia, rigidity, dyskinesias, and insomnia in PD, the investigators said.

To assess the safety and efficacy of light therapy as a novel treatment for PD, they studied 31 adults (age range, 32-77 years) who had a mean disease duration of 6 years. These study participants were randomly assigned to use 1 hour of exposure to 10,000 lux of bright light (16 patients in the intervention group) or 1 hour of exposure to less than 300 lux of dim red light (15 control subjects) every morning and every afternoon for 2 weeks.

The study participants – 13 men and 18 women – also wore actigraphy monitors all day and all night, completed daily sleep diaries, and noted daytime sleepiness in a log every 2 hours, 3 days per week.

Bright light significantly improved excessive daytime sleepiness as measured by the Epworth Sleepiness Scale and self-reported alertness during wake time, as well as several sleep metrics such as overall sleep quality, overnight awakenings, and ease of falling asleep. All the patients in the intervention group reported being more refreshed in the mornings during the study period, as compared with baseline.

Light therapy also improved overall PD severity as measured by the Unified Parkinson’s Disease Rating Scale, particularly in scores related to activities of daily living and motor symptoms. Moreover, this effect persisted during the 2-week washout period after treatment was discontinued, Dr. Videnovic and his associates said (JAMA Neurol. 2017 Feb 20. doi: 10.1001/jamaneurol.2016.5192).

The treatment was well tolerated. In the intervention group, one patient reported headache and another sleepiness, and in the control group one patient reported itchy eyes. The effects resolved spontaneously, and neither lead to treatment withdrawal.

“Based on these results, the next logical step is to optimize various parameters of light therapy (e.g., intensity, duration, and wavelength) not only for impaired sleep and alertness but also for other motor and nonmotor manifestation of PD,” the investigators wrote.

A major limitation of this study was that exposure to ambient light throughout the day was not measured. Some people in the control group received as much or even more light exposure than those assigned to bright-light therapy. “Future studies may be more strict in controlling such exposures,” Dr. Videnovic and his associates said.

This study was supported by the National Parkinson Foundation and the National Institutes of Health. Dr. Videnovic reported having no relevant financial disclosures. One of his associates reported ties to Merck, Phillips, Eisai, and Teva.