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From the Department of Neurology (E.Y.U., S.W.A.), University of Iowa, Iowa City; Neurology Service (E.Y.U.), Veterans Affairs Medical Center, Iowa City, IA; Departments of Biostatistics and Computational Biology (M.P.M.) and Neurology (M.P.M., P.G.C., P.A.), University of Rochester, Rochester, NY; Department of Neurology (K.S.M.), Columbia University, New York, NY; Department of Neurology (I.L.), University of Louisville, Louisville, KY; Department of Neurology (K.L.C.), University of Michigan, Ann Arbor; and Department of Neurology (J.C.G.), Massachusetts General Hospital, Boston.
Address correspondence and reprint requests to Dr. Ergun Y. Uc, Department of Neurology, University of Iowa, Carver College of Medicine, 200 Hawkins Drive-2RCP, Iowa City, IA 52242 ergun-uc{at}uiowa.edu
Objective: To investigate the incidence of and risk factors for cognitive impairment in a large, well-defined clinical trial cohort of patients with early Parkinson disease (PD).
Methods: The Mini-Mental State Examination (MMSE) was administered periodically over a median follow-up period of 6.5 years to participants in the Deprenyl and Tocopherol Antioxidative Therapy of Parkinsonism trial and its extension studies. Cognitive impairment was defined as scoring 2 standard deviations below age- and education-adjusted MMSE norms.
Results: Cumulative incidence of cognitive impairment in the 740 participants with clinically confirmed PD (baseline age 61.0 ± 9.6 years, Hoehn-Yahr stage 1–2.5) was 2.4% (95% confidence interval: 1.2%–3.5%) at 2 years and 5.8% (3.7%–7.7%) at 5 years. Subjects who developed cognitive impairment (n = 46) showed significant progressive decline on neuropsychological tests measuring verbal learning and memory, visuospatial working memory, visuomotor speed, and attention, while the performance of the nonimpaired subjects (n = 694) stayed stable. Cognitive impairment was associated with older age, hallucinations, male gender, increased symmetry of parkinsonism, increased severity of motor impairment (except for tremor), speech and swallowing impairments, dexterity loss, and presence of gastroenterologic/urologic disorders at baseline.
Conclusions: The relatively low incidence of cognitive impairment in the Deprenyl and Tocopherol Antioxidative Therapy of Parkinsonism study may reflect recruitment bias inherent to clinical trial volunteers (e.g., younger age) or limitations of the Mini-Mental State Examination–based criterion. Besides confirming known risk factors for cognitive impairment, we identified potentially novel predictors such as bulbar dysfunction and gastroenterologic/urologic disorders (suggestive of autonomic dysfunction) early in the course of the disease.
Abbreviations: CI = confidence interval; COWA = Controlled Word Association task; DATATOP = Deprenyl and Tocopherol Antioxidative Therapy of Parkinsonism; DLB = dementia with Lewy bodies; DST = Digit Span Test; MMSE = Mini-Mental State Examination; NDT = New Dot Task; OMO = Odd Man Out test; PD = Parkinson disease; PDD = dementia in Parkinson disease; PIGD = postural instability and gait difficulty; SDMT = Symbol Digit Modalities Test; SRT = Selective Reminding Test; UPDRS = Unified Parkinson's Disease Rating Scale.
Supplemental data at www.neurology.org
*The list of DATATOP investigators/coordinators can be found in reference 12 as well as on the Neurology® Web site at www.neurology.org.
Supported by a grant from the Parkinson's Disease Foundation (E.Y.U.). DATATOP was supported by US Public Health Service grant NS 24778 (National Institute of Neurological Disorders and Stroke).
Disclosure: Author disclosures are provided at the end of the article.
Received April 9, 2009. Accepted in final form July 21, 2009.
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