Comorbidity in drivers with Parkinson's disease

Objectives To determine the effect of comorbidity on fitness-to-drive recommendations that physicians and on-road driving assessors make and to investigate the agreement in fitness-to-drive recommendations between physicians and on-road driving assessors. Design Retrospective. Setting Data on comorbidities associated with Parkinson's disease (PD) and fitness-to-drive recommendations were investigated. Participants Individuals with PD who underwent an official on-road test in Belgium (N = 72). Measurements Correlations between comorbidity and fitness-to-drive recommendations were calculated. Stepwise logistic regression models were used to investigate whether comorbidity was an independent predictor of fitness-to-drive recommendations (pass/fail) that the physicians or the on-road assessors made. The percentage of agreement and the prevalence and bias-adjusted kappa (PABAK) were used to investigate agreement between the physicians and the on-road assessors. Results Moderate correlations were found between comorbidity and fitness-to-drive recommendations that the physicians (ρ = 0.34, P =.004) and the on-road assessors (ρ = 0.30, P =.01) made. Comorbidity was the most important determinant (coefficient of determination = 0.16, P =.005) of the physicians fitness-to-drive recommendations. No significant effect of comorbidity on the on-road recommendations was found. The physicians and the on-road assessors agreed in 46 (64%) of the cases (PABAK = 0.46, P <.001). Conclusion Comorbidity plays a role in physicians' recommendations of fitness to drive that may explain, in part, inconsistencies between physicians and on-road assessors' fitness-to-drive recommendations. This study indicates the need for an interdisciplinary dialogue between physicians and on-road assessors to reach a comprehensive fitness-to-drive decision.