Attrition in a follow-up study of driving while impaired offenders: who is lost?

High attrition rates seriously threaten the validity of follow-up studies of criminal justice populations. This study examines attrition from a follow-up study of drink-driving offenders referred 5 years earlier to a screening programme. The aim of the study was to determine which factors are most closely associated with: (1) inability to locate subjects, (2) subjects' refusal to participate; (3) the manner in which subjects refuse. Logistic regression models compared the following groups of subjects: located vs not located; interviewed vs not interviewed; type of refusal (direct vs indirect). Independent variables included gender, age group, ethnicity, whether the subject had a telephone, compliance with and completion of the screening programme, alcohol dependence or abuse diagnosis vs no diagnosis, breath-alcohol level (BAL) at the time of arrest, and whether the subject had an outstanding arrest warrant. Some factors (younger age, screening compliance, Mexican national ethnicity, and having an outstanding arrest warrant) predicted both inability to locate and type of refusal. Hispanic ethnicity and having a telephone predicted better success with locating subjects. Among refusers, non-Hispanic whites were more likely than other ethnic groups to refuse directly, and those with warrants were more likely to refuse indirectly. Non-compliance with the screening programme was also associated with differential follow-up rates. Neither arrest BAL nor alcohol diagnoses was associated with differential rates of follow-up. We conclude that alcohol diagnosis does not appear to influence successful follow-up in this criminal justice population. Rather, tracking and interviewing challenges differed among ethnic groups, suggesting a need for culturally sensitive recruitment strategies in these populations.