Daytime sleepiness in Parkinson's disease in relation to other symptoms, disease progression and daily life

Abstract: The aim of this doctoral thesis is to explore daytime sleepiness (DS) in Parkinson’s disease (PD). The Papers will evaluate how DS is connected to both motor and non-motor symptoms in PD, changes in DS over time, and the consequences of DS for the daily life of people with PD. Paper I is a multicentre study with 118 participants from four university movement disorder clinics in Sweden. The aims of this study were to (1) explore the relationship between excessive daytime sleepiness (EDS) and other symptoms of PD, and (2) to discover if there are PD symptoms that can predict the prevalence of EDS. Our results showed a weak correlation between EDS and the following: fatigue, depressive and anxiety symptoms, non-specific pain and, axial/postural/gait-related motor symptoms (PIGD phenotype) for people with PD. The factor analysis showed no interrelationship with other symptoms of PD; therefore, EDS seems to be a separate manifestation in PD. Paper II is a longitudinal study with 30 participants younger than 65, from an outpatient hospital clinic in Stockholm, Sweden. The participants were followed for up to 10 years depending on the progression of PD symptoms, especially EDS and other non-motor features. Seventeen participants completed the study. EDS was stable during the follow-up period at the group level but showed variation for individuals from year to year. EDS did not deteriorate in parallel with motor symptoms and disease severity in PD. Paper III is a study about daytime sleepiness and motor and non-motor fluctuations in PD. Fifty-three people with PD who had been investigated with DaTSCAN to verify the PD diagnosis participated in this study. The three-day patient home diary and a six-day actigraphy Parkinson’s KinetiGraphTM (PKG) were used for data collection. The items in the patient home diary were: feeling sleepy; low mood; anxiety and motor symptoms. These conditions correlated with each other and indicated that daytime sleepiness fluctuates with motor and non-motor symptoms in PD, but not with the PKG data. Paper IV is a qualitative study of people with PD and their unique experience of daytime sleepiness and the consequences in their daily life. Twelve people participated in this face- to-face interview study. The impact of daytime sleepiness was not a constant experience but depended on the resilience of the individual and their ability to handle and resist sleepiness. DS could interfere with their daily life by reducing their self-compassion and need to struggle against it. Napping could also be a powerful method for recovery and refreshing the body and brain. In summary, daytime sleepiness is a multi-factorial and multi-dimensional feature in PD. Excessive daytime sleepiness is not a stable phenomenon over time but can vary greatly for individuals from year to year, and did not deteriorate as motor symptoms in PD did. Daytime sleepiness fluctuates with motor and other non-motor symptoms like low mood and anxiety. Personal resilience can affect how people with PD can resist the sleepiness or use the recovery effect of napping to refresh the body and brain during the daytime.