Background: Little is known regarding the cognitive impairment in subjects with early, drug-naïve Parkinson disease (PD). The aim of this study was to explore the proportion with mild cognitive impairment (MCI) and subtypes in an incidence cohort of untreated PD in Southern and Western Norway. Methods: A total of 196 non-demented, drug-naive patients who were recruited after an extensive search of all new cases of PD in the area and 201 healthy control subjects completed a battery of neuropsychological tests of verbal memory, visuospatial, and attentional-executive functioning. Subjects were classified as MCI if the age- and education-corrected z-score was falling 1.5 standard deviations below the mean for at least one of the cognitive domains. Results: The PD group was more impaired on all neuropsychological tests than controls, but the effect sizes were small. The largest effect size was found for verbal memory. A total of 18.9% of the patients with PD were classified as MCI, with a relative risk of 2.1 (1.2–3.6) in PD compared to the control group. Patients with PD with and without MCI did not differ significantly regarding demographic and motor features. Among PD-MCI patients, nearly two-thirds had a non-amnestic MCI subtype, and one third had an amnestic MCI subtype. Conclusions: The findings demonstrate a twofold increase in the proportion with cognitive impairment in subjects with early, untreated Parkinson disease (PD) compared to controls. This has implications for diagnosis and management of PD. AD = Alzheimer disease; aMCI-MD = amnestic multiple-domain MCI; aMCI-SD = amnestic single-domain MCI; CVLT-2 = California Verbal Learning Test II; IQCode = Informant Questionnaire on Cognitive decline in the elderly; MADRS = Montgomery and Aasberg Depression Rating Scale; MCI = mild cognitive impairment; MMSE = Mini-Mental State Examination; naMCI-MD = non-amnestic multiple-domain MCI; naMCI-SD = non-amnestic single-domain MCI; PD = Parkinson disease; RR = relative risks; UPDRS = Unified Parkinson’s Disease Rating Scale; VOSP = Visual Object and Space Perception Battery.

Psychotic symptoms substantially contribute to the burden of Parkinson disease (PD), as they are associated with increased caregiver distress,¹ risk of hospitalization and nursing home placement,^2,3 and consequently health care costs. Although psychotic symptoms associated with PD (PDP) may be heterogeneous, they are predominated by visual hallucinations with retained insight, which may progress into more complex and severe psychotic symptoms with loss of insight, including delusions.^4,5 Reported prevalence rates of hallucinations vary, most likely because of differences in patient selection and study design, ranging from 16% to 75% in prospective cross-sectional studies.⁶ Delusions affect 1% to 35% of subjects with PD.⁶ Longitudinal studies of PDP are few and usually relatively short and not population-based.^7-9 The incidence rates as well as risk factors for emergence of PDP in the general PD population remain unclear. We therefore prospectively observed a population-based prevalence cohort of patients with PD for 12 years to explore the long-term course and associated risk factors and concomitant features of PDP.

Research from JAMA Neurology — Prognosis of Mild Cognitive Impairment in Early Parkinson Disease — The Norwegian ParkWest Study