Motor impairment, depression, dementia: which forms the impression of disease severity in Parkinson's disease?

Clinical Global Impression of Severity (CGIS) is a common measure in clinical research on Parkinson's disease (PD). However, patient features that contribute to the impression of the physician remain unclear. In particular, the impact of cognitive impairment and depression is understudied.

In a nationwide study on 1449 outpatients with PD, examined by 315 office-based neurologists, PD severity was documented with the Unified Parkinson's Disease Rating Scale (UPDRS-I, II, and IV). All patients were screened with the Montgomery-Asberg Depression Rating Scale (MADRS) for depression. The diagnosis of dementia was based on Diagnostic and Statistical Manual of Mental Disorders IV Text Revision criteria. Each patient was rated on the CGIS.

CGIS ratings were available for 1438 patients, of which 50.8% were rated as "borderline" to "moderately ill" and 49.2% as "markedly" to "extremely ill." Worse ratings were associated with higher age (p < 0.001), longer PD duration (p < 0.001), and female sex (p < 0.001). The impact of patient and physician variables on CGIS rating was calculated with three regression models (A: single bivariate regression; B: multivariate regression; and C: multivariate, multilevel regression, including physician variables). In all models, higher UPDRS-II scores and longer disease duration of PD were the strongest predictors for a worse CGIS rating. In the multivariate models (B and C), neuropsychiatric symptoms were unrelated to the CGIS rating.

The additional burden of dementia and depression was underestimated in the CGIS rating, suggesting that they are possibly relativized against the motor impairment.