• Oliver Riedel, Jens Klotsche, Annika Spottke, Günther Deuschl, Hans Förstl, Fritz Henn, Isabella Heuser, Wolfgang Oertel, Heinz Reichmann, Peter Riederer, Claudia Trenkwalder, Richard Dodel, and Hans-Ulrich Wittchen.
• Institute of Clinical Psychology and Psychotherapy, Technical University of Dresden, Chemnitzer Strasse 46, Dresden, Germany.
• J. Neurol. 2008 Feb 1;255(2):255-64.

BackgroundParkinson's disease (PD) is often accompanied by non-motor complications, such as dementia, depression, and psychotic symptoms, which worsen the prognosis and increase the personal and socioeconomic burden of disease. Prevalence estimates of these complications are quite variable and are lacking for the outpatient care sector.MethodsAs part of a larger, nationwide, cross-sectional epidemiological study in n = 315 neurological outpatient settings in Germany, this paper estimates the frequency of dementia and cognitive impairment in n = 873 outpatients meeting the UK Brain Bank criteria for idiopathic PD. Assessments were based on a clinical interview and neuropsychological assessments, including the Hoehn & Yahr rating and Unified Parkinson's Disease Rating Scale (UPDRS). Cognitive impairment was assessed by the Mini-Mental State Exam (MMSE), Clock Drawing Test (CDT) and the Parkinson Neuropsychometric Dementia Assessment (PANDA) and the clinician's diagnosis of dementia was based on the diagnostic criteria of DSMIV.ResultsUsing standardized cutoff scores, the prevalence of cognitive impairment in the study sample as measured by various methods was 17.5% by MMSE (< or = 24), 41.8% by CDT (> or = 3), 43.6% by PANDA (< or = 14), and 28.6% met the DSM-IV criteria for dementia. All estimates increased with age and PD severity. Gender was an inconsistent contributor while illness duration had no significant impact on cognition. Multiple regression analyses revealed PD severity to be the strongest predictor of dementia risk (OR = 4.3; 95% CI: 2.1-9.1), while neuropsychiatric syndromes had independent, although modest additional contributions (OR = 2.5, 95% CI: 1.6-3.8).ConclusionEstimates of cognitive impairment and dementia in PD patients are largely dependent on the diagnostic measure used. Using established clinical diagnostic standards for dementia the overall rate on routine outpatient neurological care is 28.6%, but using more sensitive neuropsychological measures, rates for cognitive impairment might be up to 2-fold higher. The MMSE revealed strikingly low sensitivity. Neuropsychiatric syndromes, in addition to PD severity and age, have an independent--although modest--additional contribution to patients' risk for cognitive impairment and dementia.

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