Are cognitively impaired individuals adequately represented in community surveys? Recruitment challenges and strategies to facilitate participation in community surveys of older adults. A review.

BACKGROUND: Dementia is the most important age-related disorder and subject to a substantial body of epidemiological research. However, field work in elderly populations faces special challenges which may reduce response rates and invalidate survey results. Therefore, this paper will review more recent prevalence studies of dementia to examine how recruitment issues and their influence on the study outcome have been addressed.
METHODS: Field studies of the elderly with the main focus on prevalence of dementia published over the last 10 years will be systematically reviewed. The review concerns sampling frames, ways to include institutionalised individuals, response rates and strategies to deal with special challenges of field work in elderly populations such as mortality, fragility and sensory impairment. Furthermore, papers were evaluated regarding the extent to which recruitment outcomes were discussed.
RESULTS: The literature is characterised by a disregard of recruitment issues to a varying extent. Mortality, functional dependency and sensory impairment (all positively related to dementia) are barely taken into account in the study design and rarely discussed. As a consequence, cognitively impaired individuals are likely to be underrepresented in most community studies.
CONCLUSION: Strategies to deal with special challenges of field work in the elderly in a systematic manner and to facilitate participation in population surveys of the elderly are crucial and will be outlined. Communication on recruitment issues is essential to improve the validity of study outcomes.