Objective: Calculation of incidence of dementia and AD, including cases in the earliest phases of the diseases.
Background: Establishment of incidence estimates is important for the future planning of the health care system, and incidence studies can offer insights into risk factors.
Methods: A total of 5,237 persons age 65 to 84 years were randomly drawn among people living in the municipality of Odense, Denmark. Of this sample 3,086 persons were eligible for the incidence study. All participants were examined with CAMCOG, the cognitive section of The Cambridge Examination for Mental Disorders of the Elderly (CAMDEX), and the follow-up period was 2 years. Using multiple linear regression, the CAMCOG cutoff score was individualized to detect even minor cognitive decline with optimal precision. Possibly demented persons were further examined with the remaining part of the CAMDEX and neuropsychological tests. AD was diagnosed according to National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorders Association criteria for probable AD, and vascular dementia and dementia of other types were diagnosed according to Diagnostic and Statistical Manual of Mental Disorders (3rd ed., revised) criteria for dementia. Finally, the severity of dementia was determined according to the Clinical Dementia Rating scale.
Results: The incidence rate for very mild to severe dementia was 29.5 per 1,000 person-years and 20.9 for AD, and the rates were similar for men and women.
Conclusion: Application of an individualized cutoff for the screening instrument resulted in detection of a substantial number of cases with very mild dementia, which subsequently resulted in higher incidence rates than those reported in most other studies.