ENLITE PD: A Randomized Clinical Trial of Light Therapy for Impaired Sleep in Parkinson's Disease

Background: Light therapy (LT) in Parkinson's disease improves sleep. Specific LT parameters require further study, including optimal frequency. Objectives: We aimed to determine if once- or twice-daily bright white light therapy (BWLT) improves sleep. Secondary aims compared once-weekly BWLT to twice-daily dim red light therapy (DRLT) as controls, estimated effects on fatigue, and adherence. Methods: A 16-week, randomized, phase 2, sham-controlled, dose-selection trial to select the superior BWLT frequency based on change in Parkinson's Disease Sleep Scale-2 (PDSS-2), participant burden, and safety. Participants were randomized to 8 weeks of twice-daily BWLT, once-daily BWLT, once-weekly BWLT, or twice-daily DRLT. An improvement of ≥1.7 points in 8-week change of PDSS-2 by daily BWLT relative to either control warranted advancing to a phase 3 trial. Results: A total of 150 participants were randomized (mean [SD], 67 [8.6] years; 57 [38%] female; PDSS-2 17.1 [6.7]). Mean 8-week change from baseline in PDSS-2 score improved (twice-daily BWLT −2.6 [95% CI: −4.4, −0.7]; once-daily BWLT -1.5 [−3.3, 0.3]; once-weekly BWLT −0.4 [−2.2, 1.4]; twice-daily DRLT −1.8 [−3.6, 0.1]) but did not meet criteria for advancing. Mean 8-week change from baseline in Parkinson's Disease Fatigue Scale (PFS-16) score improved (twice-daily BWLT −6.4 [−9.8, −3.0]; once-daily BWLT −2.2 [−5.5, 1.1]; once-weekly BWLT −0.5 [−3.9, 2.8]; and twice-daily DRLT −3.8 [−7.3, −0.4]). Mean adherence to LT was 63%–86%. Conclusions: ENLITE-PD did not meet the criteria for advancing daily LT to a phase 3 trial. LT was safe and well-tolerated with good adherence. Once-weekly BWLT was a non-inferior control compared with twice-daily DRLT.