Parkinson's disease (PD) is a progressive neurodegenerative condition characterized by motor and non-motor symptoms that significantly impact individuals' functionality and independence, reducing their quality of life (QoL). The QoL of people with PD can be influenced by several factors, including disease progression, the presence of comorbidities, and treatment response. Thus, understanding the relationship between PD severity and QoL is essential for optimizing rehabilitation strategies, enabling the implementation of more effective and personalized approaches to minimize the negative impacts of the disease.

To assess the relationship between PD severity and the quality of life of individuals affected by Parkinson’s disease.

A cross-sectional study was conducted with individuals diagnosed with PD, recruited from Parkinson’s disease associations in Rio Grande do Sul, Brazil. The study was approved by the Research Ethics Committee. Disease severity was measured using the Hoehn & Yahr Scale (H&Y), which classifies Parkinson’s disease into stages based on a combination of clinical characteristics and disability. Quality of life was assessed using the Parkinson’s Disease Questionnaire-39 (PDQ-39), which evaluates individuals' perceptions of QoL, participation, and disease-related restrictions. The comparison between variables was analyzed using a four-way ANOVA test, with post hoc analyses corrected by Bonferroni adjustments.

A total of 27 individuals were included (mean age: 70.14 years, 66% male). The four-way ANOVA indicated a significant effect on QoL among individuals with different levels of PD severity (p = 0.011). Post hoc tests revealed large and moderate effect sizes, with Cohen’s d ranging from -0.460 to -1.084. Statistical significance was reached only in the comparison between the H&Y 1.5 and H&Y 3 groups (d = -1.084, p = 0.042). Descriptive analysis showed a progressive increase in PDQ-39 scores, from 23.6 ± 5.4, 28.0 ± 12.8, 36.0 ± 9.2, and 48.0 ± 17.6 for stages 1.5, 2, 2.5, and 3, respectively, indicating that higher disease severity levels are associated with poorer quality of life.

PD severity is directly related to poorer QoL, highlighting the critical need for early and targeted interventions to minimize the negative impacts of disease progression. As the disease advances, individuals experience increasing disability and limitations, significantly affecting their daily lives. The findings of this study emphasize that individuals in more advanced disease stages, particularly those classified as H&Y stage 3, are particularly vulnerable to substantial reductions in their quality of life.

This study reinforces the importance of early and individualized rehabilitation strategies to address PD progression in its initial stages. Early recognition of disease severity through tools such as the Hoehn & Yahr scale allows for interventions that may help slow the decline in functional abilities and reduce the impact of PD on patients' lives. Furthermore, understanding the relationship between disease severity and QoL enables healthcare teams to tailor treatment plans more effectively, meeting the unique needs of each patient as they progress through the disease stages.