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

OBJECTIVES: 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.
METHODS: 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.
RESULTS: 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.
CONCLUSIONS: 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.