Death certification in treated cases of presenile Alzheimer's disease and vascular dementia in Scotland.

INTRODUCTION: although death certification data are commonly used in dementia epidemiology, their reliability has been questioned.
METHODS: death certificates were available from the Registrar General for Scotland for all patients with Alzheimer's disease/presenile dementia (AD PSD) or vascular dementia (VaD) who had died in Scotland up until 31 December 1994. Primary (immediate and underlying) and contributory causes of death were noted as well as place of death. Occupations of male patients were obtained from death certificates or from case notes and classified according to the Standard Occupational Classification. Bronchopneumonia was considered a non-specific cause of death and specific causes of death were classified as: cardiac disease, dementia, cerebrovascular disease, neoplasms, other vascular diseases and other diseases. Place of death was recorded as psychiatric hospital, district general hospital, nursing home or private residence.
RESULTS: death certificates of 398 people who had been treated for AD PSD and 348 who had been treated for VaD were identified. Bronchopneumonia was the most common immediate cause of death in the AD PSD group (70.9%) but less so for the VaD group (51.7%). For both groups place of death was associated with significant differences in pneumonia being reported as the immediate cause of death as well as specific underlying and contributory causes of death. Dementia was recorded for 90.5% of AD PSD patients but for only 49.7% of the VaD group.
CONCLUSIONS: Scottish death certificate data significantly underestimate the prevalence of presenile VaD. Changes in patterns of institutional care may affect dementia rates estimated from death certificate data.