Prevalence and Incidence of Nonmotor Symptoms in Individuals with and Without Parkinson's Disease

BACKGROUND: The prevalence ratio (PR) and incidence rate ratio (IRR) of nonmotor symptoms (NMS) were calculated for early Parkinson's disease (PD) versus non‐PD from 2 observational studies. METHODS: NMS were assessed through the self‐reported Non‐Motor Symptom Questionnaire in the online Fox Insight study and through self‐ and clinician‐rated scales in the Parkinson's Progression Marker Initiative (PPMI) study. Age‐ and sex‐adjusted/matched PR and IRR were estimated for each NMS by PD status using Poisson regression. RESULTS: Most NMS occurred more frequently in PD. Among 15,194 Fox Insight participants, sexual dysfunction had the largest adjusted PR (12.4 [95% CI, 6.9–22.2]) and dysgeusia/hyposmia had the largest adjusted IRR over a 2‐year median follow‐up (17.0 [95% CI, 7.8–37.1]). Among 607 PPMI participants, anosmia had the largest PR (16.6 [95% CI, 6.1–44.8]). During the 7‐year median follow‐up, hallucinations had the largest IRR (13.5 [95% CI, 6.3–28.8]). CONCLUSION: Although many NMS are more common in early PD than in non‐PD, their occurrence may differ with time (hallucinations) or data collection methods (sexual dysfunction).