Comparison of sleep disturbance in mild versus severe Parkinson's disease

Study objectives: To determine the effect of mild vs severe Parkinson’s disease on objective sleep parameters, in a subgroup of patients with subjective excessive daytime somnolence. Design: Patients with either mild (Hoehn and Yahr stage 1or 2) or severe (Hoehn and Yahr stage 4 or 5) idiopathic Parkinson’s disease and subjective evidence of sleepiness (Epworth sleepiness scale > 8) were recruited. All patients underwent overnight polysomnography autonomic function testing and completed questionnaires assessing quality of life, mood, and drug dosages. Mild and severe groups were then compared using the paired t-test for normally distributed data and the Mann-Whitney U test for nonparametric data. Setting: Accredited sleep centre and neurosciences unit at tertiary referral centre. Patients or participants: Parkinson’s disease outpatients referred by their treating neurologist. Interventions: N/A Results: 11 patients with mild disease and 7 with severe disease were studied. Both groups slept poorly when compared to historic normal controls. Their sleep efficiency was decreased, and the architecture fragmented. However, there was no significant difference in objective sleep parameters between the two groups. There was a significant increase in the number of voids overnight in the severe disease group (p< 0.05). Conclusions: In this subgroup of patients with subjective excessive daytime somnolence, the severity of Parkinson’s disease was not associated with a change in the measured sleep parameters. Other factors, such as drug effects, may have played a greater role. Alternatively, motor/functional measures of disease severity may poorly reflect the level of sleep disturbance. Nocturia is an important factor which disturbs sleep, particularly in the severe disease group.