Predictors of functional dependency in Parkinson’s disease

Background Functional dependency, the need for help in basic activities of daily living, is an important patient-orientated outcome. We aimed to describe the development of dependency in Parkinson’s disease (PD) and identify independent prognostic factors for this outcome. Methods We analysed data from the PINE study, a prospective, community-based incident cohort of PD with ongoing follow-up. We described the development of dependency defined by both Schwab & England score (S&E) <80% and Barthel Index <19. We identified baseline predictors of dependency using multivariable Cox regression. Results In 198 patients with PD, the rate of development of dependency was 14 per 100 person years. Older age at diagnosis (hazard ratio [HR] for 10-year increase 2.23 [95% CI 1.66–2.98]), greater smoking history (HR for 10-pack-year increase, 1.15 [1.04–1.26]), more severe axial impairment (HR for 5-point increase in sum of axial items from UPDRS scale, 1.78 [1.30–2.44]), and lower MMSE score (HR 0.88 [0.79–0.98]) were independently associated with higher risk of dependency defined by S&E. Only older age (HR for 10-year increase 1.35 [1.04–1.76]) and severity of axial impairment (HR for 5-point increase 1.85 [1.31–2.62]) were associated with higher risk of dependency defined by the Barthel Index. Sex, deprivation, co-morbidity, overall UPDRS motor score and disease stage were not independently associated with dependency. Conclusion This is the first community-based study of dependency in PD. There was a high rate of development of dependency. Older age, more smoking, more axial impairment, and poorer cognition were independent predictors.