Objective: To determine the magnitude and clinical relevance of the change of non-motor symptoms (NMS) in Parkinson’s disease (PD) patients over a 2-year follow-up.

Background: NMS are prevalent in PD and increase disability and quality of life deterioration. Quantifying the change over time and defining threshold values for a clinically relevant change are important for patients and clinicians.

Methods: International, longitudinal study of 735 PD patients assessed at baseline and two years later using Hoehn and Yahr staging (HY) and the Non-Motor Symptoms Scale (NMSS). Non-parametric tests, responsiveness statistics, three proposed distribution-based thresholds (standard error of measurement, SEM; half a standard deviation at baseline, ½ SDB; and 10% of maximum total score, MTS) and their average value (“estimated change value”, ECV) were calculated to estimate the magnitude and importance of the change.

Results: Patients, aged 65.5 (SD: 10.3), with disease duration of 6.5 (SD: 5.5) years, were predominantly male (64.7%). At baseline, 21.5% of the patients were HY stage 1, 43.9% HY2, 27.5% HY3, 5.8% HY4 and 1.2% HY5. Patients’ scores in NMSS domains Sleep/Fatigue, Perceptual problems/Hallucinations, Attention/Memory, Gastrointestinal, and Urinary, and NMSS total score were significantly worse at follow-up (p<0.001). Relative change ranged between 5.3% in Mood/Apathy domain and 26.5% in Perceptual problems/Hallucinations, with a value of 11.3% in NMSS total score. Effect sizes were from 0.04 in Mood/Apathy and Sexual function domains to 0.19 in Attention/Memory, with a value of 0.14 for the NMSS total score. SEM for domains ranged from 2.33 (Cardiovascular) to 5.75 (Miscellaneous) and was 13.2 for total score. The ECV threshold spanned from 2.06 in Cardiovascular to 5.34 in Mood/Apathy domains, and was 22.41 for NMSS total score. The observed differences in NMSS domains and total score did not reach any threshold for a clinically relevant change.

Conclusions: Some NMSS domains (Sleep/Fatigue, Perceptual problems/Hallucinations, Attention/Memory, Gastrointestinal, and Urinary) and total score showed significant worsening in the 2-year follow-up period, but the changes were relatively small and, using the proposed thresholds, not clinically relevant. Additional research to settle the suitability of these thresholds for rater-based scales is needed.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/non-motor-symptoms-trajectory-in-parkinsons-disease-magnitude-and-importance-of-the-change/