Timed Light Therapy May Benefit Sleep in Parkinson's
Improvements in disease severity were observed in both the active treatment and control groups.
Bright light therapy (LT) given twice daily significantly improved several self-reported indicators of impaired sleep and daytime alertness, both common features of Parkinson's disease (PD), according to a study reported in JAMA Neurology.
Investigators at the department of sleep medicine at Harvard Medical School and Brigham and Women's Hospital in Boston, Massachusetts and Northwestern University in Chicago, Illinois enrolled 13 men and 18 women with idiopathic PD (mean duration 5.9 years, Hoehn and Yahr stages 2 to 4) in a 2-week LT intervention study. All 31 patients had sleep impairment scores of 12 or greater on the Epworth Sleepiness Scale (ESS) at baseline and were randomized to receive either bright LT of 10,000 lux (active treatment group) or dim-red LT of <300 lux (control group) twice daily for a total intervention of 28 hours over 14 days.
Excessive daytime sleepiness (ESS) was significantly reduced, as ESS scores improved from 15.81 (3.10 standard deviation [SD]) at baseline to 11.19 (3.31 SD) after bright LT treatment, and patients reported improvements in a number of sleep metrics. Sleep fragmentation (number of overnight awakenings) was reduced from 1.51 (1.03 SD) at baseline to 0.92 (O.97 SD). Likewise, sleep quality and ease of falling asleep, both measured by sleep diary score, went from 3.53 (0.89 SD) to 3.03 (1.01 SD) and 2.32 (0.89 SD) to 1.83 (0.88 SD), respectively, following active treatment. The bright LT group also reported improvements in daytime alertness.
Quality of sleep improved in both the bright LT group and the dim red-light control group. The bright LT group showed improvements in Pittsburg Sleep Quality Index scores from 7.88 (4.11 SD) at baseline to 6.25 (4.27 SD), compared with improvements from dim-red LT, which went from 8.87 (2.83 SD) at baseline to 7.33 (3.52 SD). Parkinson's Disease Sleep Scale scores went from 97.24 (22.49 SD) to 106.98 (19.37 SD) after bright LT, and from 95.11 (19.86 SD) to 99.28 (16.94 SD) after dim-red LT. Improvements in sleep latency, total sleep time, and wake time after sleep onset were reported by both groups as well, with no significant differences between the groups.
These findings could not be readily explained. The investigators suggested several theories in addition to simple placebo effect, including the possibility of additional unintended light exposure in the control group, or a probable duration threshold of 6 to 8 weeks for the benefits of bright LT to fully emerge. They also suggested the possible impact of “anchoring the LT 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 both bright LT and dim-red LT.”
Significant improvements in PD severity, measured by Unified Parkinson's Disease Rating Scale (UPDRS) scores, were observed in both the active (39.69, 15.85 SD ) and control (45.07, 20.15 SD) groups, and persisted in UPDRS II scores after the 2-week washout period. This was attributed to improved alertness in daily activities.