The goal of this observational study is to investigate the relationship between sleep quality, cognitive functions, and disease severity in individuals with Parkinson's disease. The main question it aims to answer is:

Is sleep quality associated with cognitive function and disease severity in individuals with Parkinson's disease?

Participants will complete assessments of sleep quality, cognitive function, disease severity, and disease stage during a single evaluation session. Cognitive function will be evaluated using the Stroop Test, Clock Drawing Test, and Montreal Cognitive Assessment. Disease severity will be assessed using the Unified Parkinson's Disease Rating Scale, and disease stage will be determined using the Modified Hoehn and Yahr Scale.

Inclusion Criteria:

• Age between 40 and 65 years
• Diagnosis of Parkinson's disease confirmed by a neurologist
• Modified Hoehn and Yahr stage between 1 and 3
• Montreal Cognitive Assessment (MoCA) score ≥21

Exclusion Criteria:

• Difficulty in verbal communication
• Use of walking aid
• Severe visual impairment or additional neurological disorder
• Presence of congestive heart failure
• Any medical condition preventing participation

The study population will consist of individuals aged 40 to 65 years with Parkinson's disease who are followed at the Neurology Outpatient Clinic of Hacettepe University Faculty of Medicine. Participants who meet the eligibility criteria will be invited to participate in the study.