Effect of recruitment strategy on types of subjects entered into a primary prevention clinical trial

Clinical trials typically recruit subjects through referrals or media promotion, with generalizability of the results often uncertain. As part of a primary prevention trial to evaluate strategies for increasing physical activity in sedentary men and women, two recruitment sources, a random-digit-dial telephone survey and a community media campaign, were used to identify subjects. Baseline characteristics of 357 randomized men and women aged 50 to 65 years were compared by recruitment source. Whereas there were few differences between recruitment sources for demographic variables, telephone survey recruitment was particularly successful in recruiting smokers and persons with other cardiovascular risk factors into the trial. Counter to expectations, subsequent exercise adherence rates did not differ by recruitment source. The results suggest that the survey method, while more expensive, may be particularly useful for locating higher-risk subjects who could especially benefit from increases in physical activity but who rarely are recruited through more traditional approaches.