Sampling elderly in the community: a comparison of commercial telemarketing lists and random digit dialing techniques for assessing health behaviors and health status.
A study of health behaviors in four communities in the western United States in 1988 provided the opportunity to compare two methods of sampling elderly respondents for a telephone interview. The Polk telemarketing lists were used to identify 1,407 respondents aged 65 years and older in four communities, where 253 respondents in the same age group were also identified by the method of random digit dialing. Individuals identified from the Polk lists received a letter prior to the initial telephone contact. The overall response rate was 49.3% for random digit dialing and 57.3% for the Polk lists. On the average, the identification of one elderly respondent using the Polk lists required about 20-25% as much interviewer time per subject identified as was required by the random digit dialing method. The elderly identified by the Polk lists were significantly older than those identified by random digit dialing, and the proportions of the Polk sample who were married, white, or had an income of greater than $10,000 were slightly higher than those of the random digit dialing sample. Among 40 variables measuring various health behaviors, indicators of health status, and participation in health-related programs and classes, only three differed significantly between the two samples. The authors conclude that sampling from commercial telemarketing lists was an efficient method of identifying elderly respondents and that in these four communities, the estimates of health behaviors and health status were comparable with those obtained by random digit dialing techniques.