Sialorrhoea as a Late-Stage Marker in Parkinson's Disease: A Retrospective Cohort Analysis

Background

Sialorrhoea is a common non-motor complication of Parkinson's disease (PD), but its significance beyond symptom burden remains under-recognised. We hypothesised that referral for sialorrhoea represents a late disease milestone associated with advanced disease stage and may serve as a surrogate marker of frailty and mortality risk. 

Methods

We conducted a retrospective cohort analysis of patients referred to the Parkinson's sialorrhoea service in Cardiff and Vale between May 2021 and June 2025. Demographics, Hoehn and Yahr (H+Y) stage, age-stratified outcomes, referral timelines, and survival status were extracted from a longitudinal database. Age-stratified H+Y staging was compared with benchmark values from large Parkinson’s disease cohorts, including the UK Parkinson’s Audit and the Parkinson’s Progression Markers Initiative. Relationships between Parkinson’s disease clinic referral, sialorrhoea clinic referral, and death were analysed. 

Results

78 unique patients were referred to the specialist sialorrhoea clinic. At the time of analysis, 71 (91.0%) were deceased and 7 (9.0%) were alive. Mortality was highly age-dependent, with 96% of deaths occurring in patients aged ≥70 years. Mean H&Y stage at referral increased with age and consistently exceeded age-matched benchmarks. In patients aged 70–79 years, mean H&Y stage at referral (2.33) was higher than in comparison cohorts, including the UK audit (median H&Y ≈2) and the Parkinson Progression Marker Initiative cohort (1.6), suggesting that patients were referred at a later and more severe stage of disease. Referral typically occurred several years after initial PD clinic review, with mortality clustering in subsequent years. Older age at referral was associated with higher mortality and shorter post-referral survival, indicating a compressed terminal disease trajectory.

Conclusion

Sialorrhoea identifies a distinct late-stage Parkinson’s disease phenotype characterised by advanced H&Y staging, marked age-dependent mortality, and a compressed terminal disease trajectory. These findings support sialorrhoea as a clinically meaningful marker of advanced disease and poor prognosis, with implications for earlier escalation of supportive and palliative care strategies. Earlier identification and multidisciplinary intervention may improve patient care.