Objective: To describe the epidemiology of presenile Alzheimer's disease in Scotland from 1974 to 1988.
Design: Retrospective review of hospital records of patients aged less than 73 years admitted to psychiatric hospital with various diagnoses of dementia. Diagnoses were classified by National Institute for Communicative Disorders and Stroke and Alzheimer's Disease and Related Disorders Association Criteria and the Hachinski score. Completeness of the study sample was evaluated by scrutiny of neurology outpatient and general hospital records.
Setting: All general psychiatric hospitals in Scotland.
Subjects: All patients with onset of dementia aged 40-64.
Main outcome measures: Probable and broad Alzheimer's disease, sex of patient, age at onset.
Results: 5874 psychiatric hospital records, 129 neurology outpatient records, and 89 records from non-psychiatric hospitals were examined. 317 patients met criteria for probable Alzheimer's disease, 569 met criteria for broad Alzheimer's disease, and 267 met those for multi-infarct dementia. Minimal incidences per 100,000 population aged 40-64 years were 22.6 (95% confidence interval, 20.2 to 25.2) and 40.5 (38.9 to 42.3) per 100,000 for probable and broad Alzheimer's disease. In the 1981 census year the annual incidence of probable Alzheimer's disease was 1.6 (1.0 to 2.6). Women were at greater risk with incidence rates for probable Alzheimer's disease of 28.2 (24.5 to 32.4) per 100,000 compared with 16.5 (13.8 to 19.8) per 100,000 for men. The incidence per 100,000 for multi-infarct dementia was greater in men (25.1, 23.3 to 27.1) than women (13.4, 12.1 to 14.8).
Conclusion: Female sex seems to be positively associated with development of Alzheimer's disease before age 65 years.