Mediation Effects of Biobehavioral Factors in a Trial of Pharmacotherapy and Intensive Cessation Counseling for People with HIV Who Smoke Cigarettes in Nairobi, Kenya

There is growing recognition of the important health risks of tobacco use in people with HIV (PWH). Multiple randomized controlled trials have tested cessation treatments in this population, but little is known about factors that mediate successful quitting. We conducted a randomized, placebo-controlled 2 × 2 factorial design trial of a behavioral intervention (Positively Smoke Free [PSF] one-on-one counseling) vs. brief advice to quit ± bupropion vs. placebo in PWH who smoked cigarettes in Nairobi, Kenya. Abstinence from cigarettes was assessed by self-report and exhaled carbon monoxide (ECO). We conducted pre-planned analyses of putative mediators of the effects of bupropion (i.e. craving, withdrawal, negative affect) and of PSF counseling (i.e. abstinence self-efficacy, decisional balance, and loneliness) at 12-weeks on biochemically-confirmed abstinence at 36-weeks. 269 participants were included in the final analytic cohort (mean age = 42.7 years, 70.3% male, smoking a mean of 10.6 cigarettes per day). The biochemically verified abstinence rate at 36-weeks was 24.2%. PSF counseling increased abstinence self-efficacy and reduced loneliness significantly more than brief advice to quit at 12-weeks. Mediation analyses suggested a mediating effect of change in self-efficacy at 12-weeks in the relationship of PSF to abstinence at 36-weeks. None of the putative mediators demonstrated a significant mediation effect of bupropion on quitting. These results indicate that self-efficacy was one mechanism through which PSF counseling, but not bupropion, increased smoking abstinence among PWH who smoked cigarettes in Nairobi, Kenya.