Do tobacco regulatory and economic factors influence smoking cessation outcomes? A post-hoc analysis of the multinational EAGLES randomised controlled trial

Introduction We previously reported global regional differences in smoking cessation outcomes, with smokers of US origin having lower quit rates than smokers from some other countries. This post-hoc analysis examined global regional differences in individual-level and country-level epidemiological, economic and tobacco regulatory factors that may affect cessation outcomes.Methods EAGLES (Evaluating Adverse Events in a Global Smoking Cessation Study) was a randomised controlled trial that evaluated first-line cessation medications and placebo in 8144 smokers with and without psychiatric disorders from 16 countries across seven regions. Generalised linear and stepwise logistic regression models that considered pharmacotherapy treatment, psychiatric diagnoses, traditional individual-level predictors (eg, demographic and smoking characteristics) and country-specific smoking prevalence rates, gross domestic product (GDP) per capita, relative cigarette cost and WHO-derived MPOWER scores were used to predict 7-day point prevalence abstinence at the end of treatment.Results In addition to several traditional predictors, three of four country-level variables predicted short-term abstinence: GDP (0.54 (95% CI 0.47, 0.63)), cigarette relative income price (0.62 (95% CI 0.53, 0.72)) and MPOWER score (1.03 (95% CI 1.01, 1.06)). Quit rates varied across regions (22.0% in Australasia to 55.9% in Mexico). With northern North America (USA and Canada) as the referent, the likelihood of achieving short-term abstinence was significantly higher in Western Europe (OR 1.4 (95% CI 1.14, 1.61)), but significantly lower in Eastern Europe (0.39 (95% CI 0.22, 0.69)) and South America (0.17 (95% CI 0.08, 0.35)).Conclusions Increased tobacco regulation was associated with enhanced quitting among participants in the EAGLES trial. Paradoxically, lower GDP, and more affordable cigarette pricing relative to a country's GDP, were also associated with higher odds of quitting. Geographical region was also a significant independent predictor.Trial registration number ClinicalTrials.gov, NCT01456936.