Nonmotor Symptoms Reduce Quality of Life in Parkinson′s Disease Depending on Disease Stage and Age at Onset

In this observational study, which presents a secondary analysis related to a previously published work from our group, we aimed to examine the impact of nonmotor symptom (NMS) burden on HR-QoL in 154 outpatients with Parkinson′s disease (PD), ranging from mild to moderate-advanced disease stages, with a specific focus on motor disease progression and age at onset (AAO). To this purpose, NMS burden was measured using the NMS scale (NMSS), overall HR-QoL using the Parkinson′s Disease Questionnaire-39 (PDQ-39), and sleep disturbances using the Parkinson′s Disease Sleep Scale-2nd version (PDSS-2). The scores of the three scales were correlated with motor impairment and the amount of dopaminergic therapy. Furthermore, NMSS, PDQ-39, and PDSS-2 scores were compared between early onset PD (EOPD, AAO ≤ 50) and late-onset PD (LOPD, AAO > 50), as well as between “poor sleepers” and “good sleepers” based on the validated PDSS-2 cutoff of 18/60. We found that total NMSS, PDSS-2, and PDQ-39 scores significantly increased with advancing disease stage. EOPD patients had lower NMSS and PDSS-2 global scores compared to LOPD patients, despite the latter having longer disease duration and similar PDQ-39 scores. The NMSS global score correlated with each single domain of the PDQ-39, with the strongest associations observed in the “mobility,” “activity of daily living,” and “cognition” domains. Over one-third of patients were classified as “poor sleepers” (PDSS-2 ≥ 18) and exhibited higher NMSS and PDQ-39 total scores compared to “good sleepers.” In conclusion, this study enlightens the increasing impact of NMS and sleep disturbances on patients′ HR-QoL with disease progression and across different AAO, underscoring the need to address such modifiable factors to alleviate the burden of the disease.