Influence of sleep quality, excessive daytime sleepiness, circadian features and motor subtypes on depressive symptoms in Parkinson's disease

Objectives: The diagnosis of Parkinson's disease (PD) is mainly based on the assessment of motor symptoms, although the influence of non-motor symptoms sometimes may be more significant on the patient's disability than the cardinal clinical signs of the disease. The predominant subtype of postural instability and gait disturbance is known to be associated with more severe non-motor symptoms of Parkinson's disease. Yet, the association between motor subtypes and specific mood symptoms remains understudied. The study aimed to analyze an association between sleep and chronotype signs, motor subtypes, with the severity of depressive symptoms in PD patients.

Methods: We have included 64 patients in the clinical study. The studied population was divided into the following groups: PIGD group - patients with PD and dominance of postural instability and gait disorders; non-PIGD group - patients with PD and dominance of tremor or intermediate motor subtype. We used the Unified Parkinson's Disease Rating Scale, Beck Depression Inventory, Pittsburgh Sleep Quality Index, Epworth Sleepiness Scale, and Munich Chronotype Questionnaire.

Results: Patients with the PIGD subtype have higher levels of depressive symptoms and excessive daytime sleepiness, poorer sleep quality, later sleep onset and mid-sleep, longer sleep latency, and sleep inertia. PIGD motor subtype (p < 0.001), poor sleep quality (p < 0.001), mid-sleep (p = 0.016), and sleep latency (p = 0.025) had a significant impact on the level of depression in univariate regression analysis. Still, only mid-sleep (p = 0.019) and poor sleep quality (p = 0.003) increased the probability of higher severity of depression in the multivariate model.

Conclusion: Poor sleep quality and later mid-sleep may be predictors of more severe depressive symptoms in PD.