Sleep fragmentation as an important clinical characteristic of sleep disorders in Parkinson's disease: a preliminary study

BACKGROUND: Sleep disorders are one of the earliest non-motor symptoms of Parkinson's disease (PD). Sleep disorders could, therefore, have value for recognition and diagnosis in PD. However, no unified classification and diagnostic criteria exist to evaluate sleep disorders by polysomnography (PSG). Utilizing PSG to monitor sleep processes of patients with PD and analyze sleep disorder characteristics and their relationship with demographic parameters could aid in bridging this gap. This preliminary study aimed to evaluate the clinical characteristic of sleep disorders in PD using PSG. METHODS: PSG was used to evaluate sleep disorders in 27 patients with PD and 20 healthy volunteers between August 2015 and July 2018 in Fujian Medical University Union Hospital. Total sleep time (TST), sleep efficiency (SE), total wake time, and other parameters were compared between the two groups. Finally, the correlation between sleep disorders and age, disease duration, Unified Parkinson's Disease Rating Scale-III scores, Hoehn-Yahr stage, and levodopa dose were analyzed. The main statistical methods included Chi-square test, two independent samples t test, Fisher exact test, and Pearson correlation. RESULTS: Sleep fragmentation in the PD group was significantly increased (74.1%) while difficulty falling asleep and early awakening were not, as compared to healthy controls. No significant differences were found in time in bed, sleep latency (SL), non-rapid eye movement (NREM) stage 1 (N1), N1%, N2, N2%, N3%, and NREM% between PD and control groups; but TST (327.96 ± 105.26 min vs. 414.67 ± 78.31 min, P = 0.003), SE (63.26% ± 14.83% vs. 76.8% ± 11.57%, P = 0.001), R N3 (20.00 [39.00] min vs. 61.50 [48.87] min, P = 0.001), NREM (262.59 ± 91.20 min vs. 337.17 ± 63.47 min, P = 0.003), rapid-eye-movement (REM) (32.50 [33.00] min vs. 85.25 [32.12] min, P < 0.001), REM% (9.56 ± 6.01 vs. 15.50 ± 4.81, P = 0.001), REM sleep latency (157.89 ± 99.04 min vs. 103.47 ± 71.70 min, P = 0.034) were significantly reduced in PD group. CONCLUSION: This preliminary study supported that sleep fragmentation was an important clinical characteristic of sleep disorders in PD. Whether sleep fragmentation is a potential quantifiable marker in PD needs to be further investigated in the future study.