Recruitment procedures and their impact on the prevalence of dementia. Results from the Leipzig Longitudinal Study of the Aged (LEILA75+).

Recruitment procedures may exert a considerable influence on the outcome of health surveys in the elderly. Their impact on the prevalence of dementia will be measured in an epidemiological field study in a sample of 1,692 randomly selected individuals (75+). Face-to-face interviews were conducted using SIDAM (structured interview for the diagnosis of dementia of Alzheimer type, multi-infarct dementia and dementias of other etiology according to ICD-10 and DSM-III-R). Furthermore, proxy interviews were performed with relatives of fragile and functionally dependent individuals. Considering face- to-face interviews of community-dwelling individuals, a prevalence of moderate and severe dementia of 5.3% was found. When including information on respondents by proxy and institutionalized individuals, the prevalence rate increased to 6.3 and 10.5%, respectively. It will be argued that covering the whole population in question and ensuring high response rates are central issues to minimize selection bias.