Is quality of life in non-demented Parkinson's disease patients related to cognitive performance? A clinic-based cross-sectional study.

Whilst the association between dementia and poorer health-related quality of life (Hr-QoL) in Parkinson's disease (PD) has been well established, we aimed to explore the relationship between cognitive performance and Hr-QoL in PD without dementia. Consecutive PD patients (n = 124, 54% men, age 60.4 +/- 10.3 years) judged as non-demented based on DSM-IV criteria and Mini Mental State Examination, free of other neurodegenerative diseases or psychotic difficulties and antipsychotic/antidepressive/anxyolitic treatment were assessed in a battery of neuropsychological tests. We used Parkinson's disease questionnaire (PDQ-39) to asses Hr-QoL and Beck's Depression Inventory (BDI) to quantify depression. In the univariate analysis, better performance in each of the tests evaluating visual attention/memory or visuospatial and executive functions was associated with better Hr-QoL. In multivariate analysis [adjustment for BDI score, PD severity and duration, l-dopa dose, age, sex, education, employment status and early PD onset (<50 years of age)] in which these tests were either represented by a common variable identified in a principal components analysis or were considered individually, better cognitive performance was independently associated with better Hr-QoL. The association was conditional on the level of depression, i.e., apparent only in patients with low(er) BDI scores. Cognitive performance appears associated with Hr-QoL even in non-demented PD patients.