Risk of dementia in Parkinson's disease: a community-based, prospective study.

Abstract

To calculate the incidence of and determine possible risk factors for dementia in PD. Dementia has important clinical consequences for patients with PD and their caregivers, but the incidence is unknown. A population-based cohort of nondemented patients with PD (n = 171) from the county of Rogaland, Norway, was assessed at baseline and 4.2 years later with a comprehensive evaluation of motor, cognitive, and neuropsychiatric symptoms. The diagnosis of dementia was made according to the Diagnostic and Statistical Manual of Mental Disorders, 3rd edition, revised (DSM-III-R) criteria, based on interview of the patient and a caregiver, cognitive rating scales, and neuropsychologic tests. A representative sample of 3,062 nondemented elderly subjects without PD served as control group. Forty-three patients with PD were demented at follow-up evaluation, equivalent to an incidence rate of 95.3 per 1,000 person-years (95% CI, 68.2 to 122.0). The risk for the development of dementia in patients with PD relative to the control subjects after adjusting for age, sex, and education was 5.9 (95% CI, 3.9 to 9.1). Predictive factors at baseline for dementia in PD in addition to age were Hoehn & Yahr score >2 (OR, 3.4; 95% CI, 1.3 to 8.6) and Mini-Mental State Examination score < 29 (OR, 3.3; 95% CI, 1.3 to 8.2). Patients with PD have an almost sixfold increased risk for becoming demented compared with subjects without PD.