Abstract
Background Targeting enrollment into studies on participant characteristics is increasingly possible within HMOs given improved computerized collection of individual characteristics. Some gaps remain – particularly with respect to socioeconomic status (SES). In the absence of individual-level SES data, selecting participants on area-based SES measures may be more efficient than selecting participants on simple random samples. We describe the use of an area-based measure of formal education for targeting enrollment of adults into an intervention to design and evaluate oral and print health literacy.
Methods Kaiser Permanente Georgia is one of 3 sites participating in a CRN study on health literacy. We enrolled 40–70 year olds with low, middle, and high levels of health literacy by selecting random samples within census tracts stratified according to percents of adults with a high school (HS) education or less obtained from US Census Summary File 3 records. Census tracts were stratified into tertiles of high percents (i.e. low education tertile), moderate percents, and low percents (i.e. high education tertile).
Results Sampling achieved approximately equal representation of each tertile: 34% (84 of 250) from the low education tertile, 31% (77 of 250) from the middle tertile, and 36% (89 of 250) from the high education tertile. Self-reported education varied significantly (p<0.01) with the area-based measure of education, with 33% of those in the low education tertile, but only 9.0% of those in the high education tertile, reporting HS education or less. Unadjusted oral and print health literacy scores differed significantly (p<0.01) across the tertiles – ranging from 73.8 and 77.7 in the low education tertile to 82.4 and 86.9 in the high education tertile. Adjusted for participant age, gender, and race, self-reported education of HS or less was significantly, negatively associated with mean oral and print literacy; however, the area-based percent of adults with HS education or less was not.
Conclusions In the absence of individual-level data on formal education, area-based measures of formal educational may be a useful proxy for selecting adults with a range of oral and print health literacy into a study. Individual-level formal education, however, is a stronger correlate of literacy.
