Recruitment rates in gerontological research: the situation for drug trials in dementia may be worse than previously reported.

Recruitment issues pose a major problem in dementia research. This paper aims to clarify issues involved in the recruitment of individuals suffering from dementia for research studies. Five studies conducted by the same research team are analyzed in terms of their recruitment procedures and the obstacles encountered with recruitment. Recruitment rates varied from about 80% to 1%. Rates increased according to perceptions of risk, perceptions of benefits, and exclusion criteria. Pharmacologic studies had much lower recruitment rates than nonpharmacologic studies. Investigators need to limit exclusion criteria as much as possible. The extremely low recruitment rates of pharmacologic studies in frail persons with dementia may render the results irrelevant for that population. Similarly, the major differences in procedures between pharmacologic and nonpharmacologic studies may invalidate comparisons of results among such studies. More attention needs to be given to a systematic reporting of recruitment rates.