A census-based design for the recruitment of a community sample of older adults: efficacy and costs

This is a report of the scientific and cost implications of a census-based design to identify residents aged 55 and over for a community study of the effects of aging on physical function.

A census of residents in a study community was conducted by the use of a mailed questionnaire. For households that did not complete and return the mailed census questionnaire, contact was attempted first by telephone and then by home visit. A comparison was made of the unit costs and characteristics of subjects identified by the different methods.

A total of 3509 age-eligible subjects were identified (78.3% by mailer, 19.5% by telephone, and 2.0% by home visit). Costs per enrolled age-eligible subject were lower for mailing and telephone ($7.76 and $4.72 respectively) than for home visit ($36.25). Subjects identified by home visit were significantly younger than subjects identified either by mail or telephone. After adjustment for age, subjects identified by telephone had less education and income and poorer health and functional status than subjects identified by mail. With the exception of age, there were no significant differences between subjects identified by mailer and home visit.

A mailed questionnaire with telephone recontact is a practical strategy for community-based recruitment. Recontact of subjects by telephone can be expected to identify subjects who are not well-represented in a sample based only on a mailer. In contrast, the home visit is expensive and identifies subjects who do not differ meaningfully from those identified by mailer.