For decades, bright light therapy has had a furniture problem. The classic way to treat a sleep disorder with light is to sit in front of a desktop-sized light box for half an hour or more, often at breakfast, while the glare washes over the eyes. For a person with Parkinson’s disease, whose tremor, stiffness, and fatigue make sitting still its own kind of labor, that is a genuine barrier to care. A new randomized pilot trial from the Netherlands and Poland tests whether the same idea can be compressed into a pair of glasses with light-emitting diodes built into the frames, worn for one hour twice a day while daily life continues around them.
Sleep disruption is a near-constant companion of Parkinson’s disease, and its costs spill outward. It disturbs daily functioning, darkens mood, and erodes quality of life for patients and the people who sleep beside them. Because many standard sleep aids were off the table (the trial excluded anyone using hypnotics or stimulants), non-drug options matter.
The device, made by Chrono Eyewear BV and sold under the name Propeaq, looks like a normal pair of spectacles with interchangeable lenses and integrated LEDs. In the active arm, 15 participants wore blue lenses while the glasses emitted light at 461 nm, plus or minus 10 nm, delivering a melanopic equivalent daylight illuminance of 114.38 lux at the cornea. The 15 participants in the placebo arm wore identical frames with red lenses; the LED hardware was present but inactive, and participants could not switch it on. Everyone followed the same schedule: one hour after waking in the morning and one hour starting two hours before the preferred bedtime, for two weeks.
What they found
The two groups looked alike at baseline. Average age was around 71 years, disease duration around eight years, and baseline scores on the Pittsburgh Sleep Quality Index (PSQI), where higher means worse, were 12.27 in the blue light group and 11.00 in the placebo group. Both sat far above the clinical threshold of 5.
Two weeks of treatment moved both groups, but not equally. The blue light arm improved to a PSQI of 7.87 at week 2, while the placebo arm reached 9.60; that gap was a trend, not yet significant (p = 0.065). Three weeks after treatment ended, at the week 5 follow-up, the difference had grown and crossed the significance line: 7.13 for blue light versus 9.40 for placebo (p = 0.029). The group by time interaction was significant (p < 0.001), and the effect size at week 5 was large for blue light (0.896) against a small effect for placebo (0.450).
Daytime sleepiness moved even more dramatically. Clinically relevant sleepiness, defined as a score of 10 or higher on the Epworth Sleepiness Scale, was present in half of the blue light group (50.0 percent) at baseline. By the week 5 follow-up, that share had fallen to 6.7 percent, a change significant at p = 0.005 with a large effect size of 0.918. Diary-based sleep measures told the same story, with the active arm improving across most recorded domains.
The most striking detail: these gains were measured three weeks after the glasses had been handed back. The benefit did not evaporate when the LEDs went off, hinting that two weeks of morning and evening light may nudge the circadian system in a way that outlasts the treatment.
Why it matters
Light boxes work, but they are not wearable. The glasses deliver light at a fraction of the intensity of a typical light box, a melanopic EDI of just over 114 lux at the cornea, yet they produced large effects. If replicated, that would make light therapy practical for people who cannot sit still, who travel, or who live in shared spaces where a bright lamp is intrusive. Wearing glasses while making breakfast or reading the mail is a different proposition from parking yourself in front of a lamp.
The trial also made a serious attempt at a proper control: red lenses in identical frames with a dead LED. That keeps the experience of wearing glowing glasses similar across arms, exactly what a placebo should do, even if the red light itself is not perfectly inert.
The numbers also hint at clinical meaning. A drop from 12.27 to 7.13 on the PSQI moves a person from severely disrupted sleep toward the boundary of the normal range, and taking the proportion with clinically relevant daytime sleepiness from half the group down to one in fifteen is the kind of change that alters a person’s day, not just their score sheet.
Limits
This is a pilot study, and the number that matters most is 30. Fifteen people per arm is enough to detect large effects and not much else. The trial was single-blind: participants knew what color lenses they wore, which opens the door to expectation effects. The red light placebo, though clever, is not fully inert; red light has its own physiological effects, so the contrast between arms may be larger than a truly inactive placebo would produce.
Recruitment itself reveals the pragmatics. Enrollment stretched from January 2018 to January 2023, with a nearly two-year pause imposed by the COVID-19 pandemic. The trial admitted people whose PSQI reached 5, a cutoff slightly below the customary boundary of above 5, a pragmatic choice to ease recruitment in a comorbid population, balanced by the requirement that participants also report daytime sleepiness or subjective sleep complaints. People with other sleep disorders, significant psychiatric illness, cognitive impairment (MoCA below 24), or use of sleep medications were excluded, so the results describe a relatively selected group. The trial also leaves open who benefits most, how long the effect lasts beyond five weeks, and whether people will wear the glasses daily in real life.
Bottom line
Two weeks of blue light glasses, one hour in the morning and one hour before bed, improved sleep quality and sharply reduced daytime sleepiness in people with Parkinson’s disease, with effects that outlasted the treatment. The effect sizes were large, the light dose was small, and the device is something people can wear while going about their morning. But a 30-person pilot is a proof of concept, not a prescription. The results justify larger, longer, properly blinded trials, ideally with an inert placebo, to confirm that a pair of glasses can do what a light box does, without the furniture.
Source
Śmiłowska K, de Vries NM, Bloem BR, van Wamelen DJ. Blue light therapy delivered through light glasses improves sleep quality and daytime sleepiness in Parkinson’s disease: A randomized trial. Journal of Parkinson’s Disease. Published online August 6, 2026. doi:10.1177/1877718X261468544. PMID: 42558005.