Mild Cognitive Impairment as a risk factor for Parkinson's disease dementia

Abstract

Background The International Parkinson and Movement Disorders Society criteria for mild cognitive impairment in Parkinson’s disease were recently formulated. Objectives The aim of this international study was to evaluate the predictive validity of the comprehensive (level II) version of these criteria by assessment of their contribution to the hazard of Parkinson’s disease dementia. Methods Individual patient data were selected from four separate studies on cognition in Parkinson’s disease that provided information on demographics, motor examination, depression, neuropsychological examination suitable for application of level II criteria, and longitudinal follow-up for conversion to dementia. Survival analysis evaluated the predictive value of level II criteria for cognitive decline towards dementia as expressed by the relative hazard of dementia. Results A total of 467 patients were included. The analyses showed a clear contribution of impairment according to level II mild cognitive impairment criteria, age and severity of Parkinson’s disease motor symptoms to the hazard of dementia. There was a trend of increasing hazard of dementia with declining neuropsychological performance. Conclusions This is the first large international study evaluating the predictive validity of level II mild cognitive impairment criteria for Parkinson’s disease. The results showed a clear and unique contribution of classification according to level II criteria to the hazard of Parkinson’s disease dementia. This finding supports their predictive validity and shows that they contribute important new information on the hazard of dementia, beyond known demographic and Parkinson’s disease specific factors of influence.Michael J. Fox Foundation Dutch Parkinson Foundatio