Poor sleep is common among individuals with Parkinson's disease (PD) and may affect up to 98% of patients. However, the relationship between poor sleep, cognitive aspects, and quality of life (QoL) in this population remains unclear.

To investigate the relationship between poor sleep, cognition, and QoL in individuals with Parkinson's disease.

This cross-sectional study included 53 subjects with idiopathic Parkinson's disease (PD), who were non-institutionalized and had mild to moderate PD. Sociodemographic data was collected using a questionnaire, and the following assessment tools were used: the Parkinson's Disease Sleep Scale-2 (PDSS-2) to assess the quality of sleep, the Montreal Cognitive Assessment (MoCA) to assess the cognitive status of patients, and the Parkinson's Disease Quality of Life Questionnaire (PDQ-39) to assess the QoL. Spearman correlations were used for statistical analysis, with a significance level of 5%.

Out of the 53 subjects, 34 were men and 19 were women, they had an average age of 66.62 ± 9.46. In analysing the sleep and cognition, a moderate correlation was found between the Parkinson's Disease Sleep Scale-2 (PDSS-2) and the visuospatial domain (r=-0.401; p=0.003) as well as the total Montreal Cognitive Assessment (MoCA) score (r=-0.309; p=0.024). In analysing the sleep and quality of life, a moderate to strong correlation was observed between the PDSS-2 and the PDQ-39 domains, specifically mobility (r=0.598; p=<0.001), communication (r=0.628; p=< 0.001), bodily discomfort (r=0.620; p=< 0.001), and the total score (r=0.773; p=< 0.001). Furthermore, a subanalysis by gender was performed, and the groups of men and women were found to be similar in terms of age, time of diagnosis, the stage of the disease, and the PDSS-2, PDQ-39, and MoCA scores. The results showed that in men, the PDSS-2 had a correlation with cognition, with a strong correlation observed between the PDSS-2 and the naming domain (r=-0.623; p=< 0.001), and moderate correlations with the visuospatial (r=- 0.494; p=0.003), language (r=-0.365; p=0.034), abstraction (r=-0.400; p=0.019), delayed recall (r=-0.416; p=0.014), orientation (r=-0.392; p=0.022), and the total MoCA score (r=-0.512; p=0.002) domains. In terms of QoL, women showed a strong correlation between the PDSS-2 and the Activities of Daily Living domain (r=0.685; p=0.001), bodily discomfort (r=0.649; p=0.003), and the total PDQ-39 score (r=0.728; p< 0.001). In men, a strong correlation was found between the PDSS-2 and the domains of emotional well- being (r=0.644; p=< 0.001), communication (r=0.731; p=< 0.001), bodily discomfort (r=0.718; p=< 0.001), and the total PDQ-39 score (r=0.772; p=< 0.001).

Individuals with worse sleep quality have poorer cognitive scores, particularly men. Additionally, poorer sleep quality is associated with a worse quality of life in domains such as mobility, communication, and bodily discomfort.

Screening for sleep disorders and implementing prevention and treatment strategies are necessary for individuals with Parkinson's disease (PD) who have worse sleep quality, given the negative impact on cognitive performance and quality of life. Further studies should explore the association of sleep quality with other symptoms of PD.