Poor adherence to placebo or amiodarone therapy predicts mortality: results from the CAMIAT study. Canadian Amiodarone Myocardial Infarction Arrhythmia Trial

Abstract

Objective: This study examined the relationship between adherence, mortality, and psychosocial factors.

Methods: Subjects were 1141 patients participating in the Canadian Amiodarone Myocardial Infarction Arrhythmia Trial. Poor adherence to study medication (amiodarone or placebo), measured by pill count over 2 years, was defined as the lower 20th percentile of the pill count distribution. Predictors of adherence were also studied and included demographic and cardiac variables and, in a subset of participants (N = 671), measures of depression, distress, hostility, and social support.

Results: In survival analysis controlling for cardiac and demographic variables, poor adherence in the placebo and amiodarone groups was associated with an increased risk of sudden cardiac death (relative risk (RR) = 2.11, 95% confidence interval (CI) = 1.03-4.56, p < .05; and RR = 3.15, 95% CI = 1.34-7.44, p < .01, respectively), total cardiac mortality (RR = 2.04, 95% CI = 1.12-3.72, p < .02; and RR = 2.49, 95% CI = 1.32-4.72, p < .01, respectively), and all-cause mortality (RR = 2.25, 95% CI = 1.27-3.97, p < .001; and RR = 2.34, 95% CI = 1.32-4.17, p < .004, respectively). Logistic regression analysis identified two predictors of poor adherence to placebo: age > 70 years (odds ratio = 2.18, 95% CI = 1.11-4.29, p < .03) and social activities in the month before the index heart attack (odds ratio = 1.02, 95% CI = 1.00-1.04, p < .05).

Conclusions: Poor adherence is associated with a greater risk of mortality. The relationship between adherence and social activities suggests a higher motivation to adhere to treatment in individuals more engaged in enjoyable activities.