Light Therapy May Promote Daytime Alertness and Better Sleep in Parkinson's

In a new study, when people with Parkinson’s disease (PD) who experienced daytime excessive sleepiness were exposed to bright light twice a day, using light boxes similar to those available in drug stores, they were more alert in the daytime and slept better at night. This research funded by the Parkinson’s Foundation appears in the February 20 online edition of JAMA Neurology.

Daytime sleepiness is a common symptom of PD as well as a side effect of its medications. Many people with PD also have trouble falling asleep and staying asleep at night. Though light therapy has been proven helpful to healthy older adults, and others with similar sleep difficulties, it has not been rigorously explored in Parkinson’s. Researchers led by Aleksandar Videnovic, M.D., M.Sc., at Massachusetts General Hospital in Boston, tested whether light therapy also could help people with Parkinson’s maintain a healthy sleep-wake cycle.

The study enrolled 31 people with PD who had excessive daytime sleepiness, as determined by a standard rating scale. Study participants (13 men and 18 women) had lived with PD for six years on average. None of the participants had sleep apnea or rapid-eye-movement (REM) sleep behavior disorder.

For two weeks, 16 of the participants were exposed to bright light (10,000 lux) from a conventional light box twice daily, in the morning and late afternoon. The other participants, serving as a control group, were exposed to dim-red light (less than 300 lux) as a placebo. Study participants kept sleep logs in which they recorded awakenings during the night, sleep quality, and ease of falling asleep. They also wrote down their daytime sleepiness and wore a wrist monitor that tracked their physical activity.


  • During the two weeks of light therapy, all participants had better quality sleep and reported feeling more refreshed in the morning.
  • Study participants exposed to bright light had significantly less daytime sleepiness than before participating in the study.
  • All participants increased their physical activity during the study, those receiving therapy with bright light more than those getting placebo.
  • PD movement symptoms improved in all study participants.

What Does It Mean

Excessive daytime sleepiness affects the quality of life for many people with PD. Treatments to date have been disappointing. This study finds that carefully-timed exposure to bright light may help people with PD to maintain a healthy sleep-wake cycle. This could help people to sleep better at night, and increase alertness during the day, both of which improve a person’s quality of life.

Researchers note that exposure to the outdoors, or even participation in a structured activity could explain why people in the low-light group also benefitted.

The study is important because it provides insight into how PD affects the body’s internal clock, or circadian rhythms. The brain changes that take place with PD, combined with less exposure to sunlight when people remain indoors, can throw off circadian rhythms. By timing light therapy, it may be possible to re-set them and correct the sleep-wake cycle as well other body cycles related to movement and well-being.

This research study as well as Dr. Videnovic’s previous research into the sleep were funded by both divisions of the Parkinson’s Foundation.


Videnovic A, Klerman EB, Wang W, et al. (2017). Timed Light Therapy for Sleep and Daytime Sleepiness Associated With Parkinson Disease: A Randomized Clinical Trial. JAMA Neurology 10.1001/jamaneurol.2016.5192

Högl B. Circadian Rhythms and Chronotherapeutics—Underappreciated Approach to Improving Sleep and Wakefulness in Parkinson Disease. JAMA Neurology, February 20, 2017 10.1001/jamaneurol.2016.5519 

Science News
mail icon

Subscribe here to get the latest news on treatments, research and other updates.