Research subject recruitment for gerontological studies of pharmacological agents.

Elderly subjects were recruited for a study of the effect of intravenous physostigmine on the memory disturbance of Alzheimer's Disease. Approximately one out of every twelve people screened was suitable for the study. Subjects were ruled out either because they did not meet research diagnostic criteria for AD, because they could not cooperate with the studies or because of medical contraindications. The data indicate that large numbers of potential subjects are required to select relatively small groups for pharmacological studies. The implications of some of these developments for future research are discussed.