By Daniel A. Barone, MD, FAASM
Assistant Professor of Neurology, Weill Cornell Medical College
Dr. Barone reports no financial relationships relevant to this field of study.
SYNOPSIS: Light therapy has been shown to be beneficial in treating excessive daytime sleepiness in Parkinson’s disease patients and also may improve sleep quality.
SOURCE: Videnovic A, Kierman EB, Wang W, et al. Timed light therapy for sleep and daytime sleepiness associated with Parkinson disease: A randomized clinical trial. JAMA Neurol 2017; 74:411-418.
Parkinson’s disease (PD), which affects more than 1 million people in the United States, is the second most common neurodegenerative disorder. Although it is known for the classic tetrad of motor symptoms including bradykinesia, tremor, rigidity, and postural instability, sleep disturbances are common as well. For example, excessive daytime sleepiness (EDS) and nocturnal sleep fragmentation affect up to 90% of patients with PD. There is currently a paucity of available treatments for the sleep abnormalities noted in PD patients, and as the authors of this paper reported, there is a great need to develop nonpharmacological approaches to prevent and manage sleep disorders in these patients.
The cause of sleep disturbances in PD patients is attributed to the symptoms of PD itself, the adverse effects of medications, a primary neurodegeneration of central sleep regulatory areas, and disruption of circadian rhythms. Circadian rhythms are generated by a pacemaker located in the suprachiasmatic nucleus of the hypothalamus and produce endogenous physiologic cycles that occur approximately every 24 hours. Social and environmental cues help synchronize the circadian rhythms, and light is the most effective zeitgeber (time-giver) of the circadian system.
Bright light has beneficial effects on sleep quality and daytime vigilance in healthy older people and patients with dementia, and has been applied in a variety of sleep and neuropsychiatric conditions. While a few preliminary studies found significant improvements in depression, bradykinesia, rigidity, dyskinesias, and insomnia symptoms with supplemental light exposure in PD, this study was designed to assess the safety and efficacy of light therapy as a novel treatment approach to excessive daytime sleepiness associated with PD.
To accomplish this, the authors randomized participants with PD who had concomitant EDS to receive either bright light therapy (10,000 lux) or dim-red light (control condition, < 300 lux) for 14 days, twice daily. The study was performed in PD centers at Northwestern University and Rush University, and included participants with PD receiving stable dopaminergic therapy with coexistent EDS, as assessed by an Epworth Sleepiness Scale score of ≥ 12, and without cognitive impairment or a primary sleep disorder.
A change in the Epworth Sleepiness Scale score was the primary outcome measurement comparing bright light therapy with dim-red light therapy. The Pittsburgh Sleep Quality Index score, the Parkinson’s Disease Sleep Scale score, the visual analog scale score for daytime sleepiness, and sleep log-derived and actigraphy-derived metrics were considered secondary outcome measures.
Sixty-three patients were assessed for eligibility, but 32 were excluded for either refusing to participate (18) or failing to meet inclusion criteria (14). Among the 31 patients (13 males and 18 females; mean [SD] disease duration, 5.9 [3.6] years), 16 (mean age 62.31 [10.83] years of age, eight women) were randomized to receive bright light therapy, and 15 (mean age 64.07 [8.89] years of age, 10 women) were randomized to receive dim-red light therapy.
Bright light therapy resulted in significant improvements in excessive daytime sleepiness, with mean Epworth Sleepiness Scale scores at baseline of 15.81 (3.10) reducing to 11.19 (3.31) after the intervention. Both bright light and dim-red therapies were associated with improvements in sleep quality, as assessed via mean scores on the Pittsburgh Sleep Quality Index (7.88 [4.11] at baseline reducing to 6.25 [4.27] after bright light therapy, and 8.87 [2.83] at baseline reducing to 7.33 [3.52] after dim-red light therapy). Similarly, the Parkinson’s Disease Sleep Scale reduced in both cases (97.24 [22.49] at baseline vs. 106.98 [19.37] after bright light therapy, and 95.11 [19.86] at baseline vs. 99.28 [16.94] after dim-red light therapy).
Bright light therapy also improved several self-reported sleep metrics, including sleep fragmentation, sleep quality, and ease of falling asleep, and was associated with increased daily physical activity as assessed by actigraphy.
Light therapy was well tolerated; within the bright light therapy group, two participants reported one adverse effect each of headache and sleepiness and one participant in the dim-red light therapy group reported itchy eyes. In all cases, the adverse effects resolved spontaneously. Thus, the authors concluded that bright light therapy may be a safe and effective intervention for improving sleep and alertness in patients with PD.
COMMENTARY
While it is clear that bright light therapy can be an effective treatment, this study was relatively short and the improvements modest. Furthermore, there are other concerns with bright light therapy; there is a possible association of PD with bipolar disorder, and it is well-known that the use of bright light therapy in patients with bipolar disorder may trigger a manic episode. As with any treatment modality, careful selection of appropriate patients would need to be exercised. Overall, this was a well-designed and executed study. Hopefully, longer-term and more robust trials will shed further light on the tolerability, safety, compliance, and effectiveness of this promising therapy.
Light therapy has been shown to be beneficial in treating excessive daytime sleepiness in Parkinson’s disease patients and also may improve sleep quality.
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