A population-based study on the incidence of dementia disorders between 85 and 88 years of age

OBJECTIVE: To investigate the incidence of Alzheimer's disease, vascular dementia and other dementias in a population between 85 and 88 years of age. DESIGN: Prospective cohort study. Longitudinal population study of the very old. SETTING: Systematic sample of a birth cohort living in the community or in institutions in the city of Gothenburg, Sweden. PARTICIPANTS: A representative population sample of nondemented 85-year-old residents (n = 347). MEASUREMENTS: The study included neuropsychiatric, neuropsychological, and physical examinations, key informant interviews, comprehensive laboratory tests, electrocardiography, chest radiography and computed tomography (CT-scan) of the head. Information on subjects lost during the follow-up period as a result of death or refusal was traced in medical records. Dementia was defined according to the criteria proposed in the Diagnostic and Statistical Manual of Mental Disorders (3rd Edition, revised), Alzheimer's disease according to the criteria of the National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer's Disease and Related Disorders Association, and vascular dementia according to criteria proposed by Erkinjuntti. RESULTS: Sufficient information was obtained about 92% of the subjects at risk. Sixty-three subjects (18.2%) became demented between ages 85 and 88, giving an incidence of 90.1/1000/year (61.3/1000/year for men and 102.7/1000/year for women; P = .085). The incidence of Alzheimer's disease was 36.3/1000/year, vascular dementia 39.0/1000/year (P = 1.000), and that of other dementias 9.1/1000/year. CONCLUSION: This study shows that almost one-tenth of nondemented persons between the ages of 85 and 88 become demented each year, emphasizing the magnitude of the dementia problem in the very old, the fastest growing segment of western populations.