Incidence of dementia with Lewy bodies and Parkinson disease dementia.

IMPORTANCE Epidemiologic data on dementia with Lewy bodies (DLB) and Parkinson disease dementia (PDD) remain limited in the United States and worldwide. These data are essential to guide research and clinical or public health interventions. OBJECTIVE To investigate the incidence of DLB among residents of Olmsted County, Minnesota, and compare it with the incidence of PDD. DESIGN The medical records linkage system of the Rochester Epidemiology Project was used to identify all persons who developed parkinsonism and, in particular, DLB or PDD from 1991 through 2005 (15 years). A movement disorders specialist reviewed the complete medical records of each suspected patient to confirm the diagnosis. SETTING Olmsted County, Minnesota, from 1991 through 2005 (15 years). PARTICIPANTS All the residents of Olmsted County, Minnesota, who gave authorization for medical record research. MAIN OUTCOMES AND MEASURES Incidence of DLB and PDD. RESULTS Among 542 incident cases of parkinsonism, 64 had DLB and 46 had PDD. The incidence rate of DLB was 3.5 per 100,000 person-years overall, and it increased steeply with age. The incidence of PDD was 2.5 overall and also increased steeply with age. The incidence rate of DLB and PDD combined was 5.9. Patients with DLB were younger at onset of symptoms than patients with PDD and had more hallucinations and cognitive fluctuations. Men had a higher incidence of DLB than women across the age spectrum. The pathology was consistent with the clinical diagnosis in 24 of 31 patients (77.4%) who underwent autopsy. CONCLUSIONS AND RELEVANCE The overall incidence rate of DLB is lower than the rate of Parkinson disease. The incidence of DLB increases steeply with age and is markedly higher in men. This men to women difference may suggest different etiologic mechanisms. Our findings may guide health care planning and prompt new studies.