Baseline trajectories of heavy drinking and their effects on postrandomization drinking in the COMBINE Study: empirically derived predictors of drinking outcomes during treatment
The COMBINE Study sought to answer questions about the benefits of combining behavioral and pharmacological interventions (naltrexone and acamprosate) in alcohol-dependent patients. Our goals were to identify trajectories of heavy drinking prior to randomization in COMBINE, to characterize subjects in these trajectories, and to assess whether pre-randomization trajectories predict drinking outcomes. We analyzed daily indicators of heavy drinking in 90 days prior to randomization using a trajectory-based approach. Each subject was assigned to the most-likely pre-randomization heavy drinking trajectory, and the baseline characteristics of participants in the baseline trajectories were compared. Main and interactive effects of these trajectories and treatment factors (acamprosate, naltrexone or CBI) on summary drinking measures during active treatment (16 weeks) were assessed. We identified five trajectories of heavy drinking pre-randomization: “T1: frequent heavy drinkers”, “T2: very frequent heavy drinkers”, “T3: nearly daily heavy drinkers”, “T4: daily heavy drinkers” and “T5: daily heavy drinkers stopping early” prior to randomization. Trajectory membership was significantly associated with all drinking outcomes. Subjects in “T5: daily heavy drinkers stopping early” had comparable drinking outcomes to the subjects in “T1: frequent heavy drinkers” while the remaining trajectories were associated with significantly worse outcomes. Baseline trajectory did not interact significantly with treatment condition. These exploratory analyses confirmed the hypothesis that baseline trajectories predict post-randomization drinking outcomes. Interestingly, “T5: daily heavy drinkers stopping early” had outcomes that were comparable to the least severe baseline trajectory “T1: frequent heavy drinkers” and baseline trajectories of heavy drinking did not moderate treatment effects
