A Cochrane review included 37 RCTs involving mostly older male patients with CHD, predominantly myocardial infarction. The effect of interventions on abstinence after 6 to 12 months was positive (RR 1.22, 95% CI 1.13 to 1.32; 37 trials, n=7 682 , I²= 54%; abstinence rate: treatment group = 46%, control group 37.4%). Studies with validated assessment of smoking status at follow-up had similar efficacy (RR 1.22, 95% CI 1.07 to 1.39) to non-validated trials (RR 1.23, 95% CI 1.12 to 1.35). Studies were clustered by intervention strategy and intensity of the intervention. Clustering reduced heterogeneity, although many trials used more than one type of intervention. The RRs for different strategies were similar (behavioural therapies RR 1.23, 95% CI 1.12 to 1.34, I²= 40%; telephone support RR 1.21, 95% CI 1.12 to 1.30, I²= 44%; self-help material RR 1.22, 95% CI 1.12 to 1.33, I²= 40%). More intense interventions showed increased quit rates (RR 1.28, 95% CI 1.17 to 1.40, I²= 58%) whereas brief interventions did not appear effective (RR 1.01, 95% CI 0.91 to 1.12, I²= 0%). 7 trials had longer term follow-up, and did not show any benefits after 12 months.
Comment: The quality of evidence is downgraded by indirectness (smoking status was seldom validated).