Using direct mail to recruit Hispanic adults into a dietary intervention: an experimental study

Identifying strategies for successful recruitment of ethnic minorities into scientific studies is critical. Without effective methods, investigators may fail to recruit the desired sample size, take longer to recruit than planned, and delay progress for research in minority health. Direct mail is an appealing recruitment method because of the potential for reaching large target populations and producing a high volume of inquiries about a study with relatively little staff effort. To determine which of three direct mail strategies yielded higher recruitment, 561 Hispanic employees were randomly assigned to receive either: (a) a flyer about a worksite dietary intervention; (b) the same flyer plus a personalized hand-signed letter containing heart disease risk statistics for the general American population; or (c) the flyer plus a personalized hand-signed letter containing statistics for Hispanics. Two orthogonal chi-square comparisons were examined. The personalized letters plus flyer yielded a significantly higher response rate (7.8%) than the flyer alone (2.1%), X2(1, N = 561) = 7.5, p = .006. However, the personalized letter with Hispanic heart disease risk statistics did not yield a statistically significant higher response rate (9.1%) than the letter with the general population risk statistics (6.5%), X2(1, N = 370) = 0.9, p > .34. These findings suggest that personalized approaches can increase the effectiveness of direct mail efforts for recruiting ethnic minorities into interventions and may be particularly helpful for large-scale interventions.