Tracking and incentivizing substance abusers in longitudinal research: results of a survey of National Institute on Drug Abuse-funded investigators.

Abstract

Increased recognition that addictive behaviors tend to be chronic and relapsing has led to a growing emphasis on longitudinal substance abuse research. The purpose of this study was to identify effective follow-up strategies used by National Institute on Drug Abuse-funded investigators who have conducted at least 1 study involving follow-up data collection from human subjects. A web-based survey was administered to a representative sample of National Institute on Drug Abuse-funded researchers (N = 153) with a history of conducting longitudinal research. Reported study response rates were generally high, although 27% of the studies fell below the 80% benchmark. Face-to-face and telephone-based interviews commanded the largest subject payments-2 to 3 times higher than compensation rates for collection of biologic samples. With regard to the presumed impact of low follow-up rates on the generalizability of study findings, one-third of investigators who compared baseline characteristics of those who did and did not participate in the follow-up found meaningful differences. Support was found for the hypothesis that follow-up rates and total compensation would be positively related, with the mean compensation amounts between studies achieving <80% follow-up rate versus those achieving rates ≥80%, revealing a statistically significant effect in the predicted direction. The majority of respondents reported difficulty in tracking and locating subjects, and study respondents often proved to be quite different from nonrespondents. Incentives improved follow-up rates to a point, although the relationship was not linear. Efforts to improve follow-up rates may be better spent on addressing tracking and locating logistics rather than on strategies to compel participation once the subject has been located.