Population-level predictors of changes in success rates of smoking quit attempts in England: a time series analysis

Aims: To quantify associations between the success of smoking quit attempts and factors that have varied throughout 2007–2018 at a population level. Design: time series analysis using Autoregressive Integrated Moving Average with Exogeneous Input (ARIMAX) modelling. Setting and Participants: Data were aggregated from 54 847 past-year smokers taking part in the Smoking Toolkit Study which involves monthly repeated cross-sectional household surveys of individuals aged 16+ in England. Measurements: The input series were: (1) attempts at smoking reduction using (a) e-cigarettes and (b) nicotine replacement therapy (NRT); (2) use during a quit attempt of (a) e-cigarettes, (b) NRT over-the-counter, (c) medication on prescription and (d) face-to-face behavioural support; (3) use of roll-your-own tobacco; (4) prevalence of (a) smoking and (b) non-daily smoking; (5) tobacco control mass media expenditure; (6) expenditure on smoking; (7) smoker characteristics in the form of (a) high motivation to quit, (b) average age, (c) socio-economic status and (d) cigarette consumption; (8) implementation of tobacco control policies; and (9) quit attempt rate. Findings: The licensing of NRT for harm reduction was associated with a 0.641% [95% confidence interval (CI) = 0.073–1.209, P = 0.027] increase in the mean point prevalence of the success rate of quit attempts. For every 1% increase in the mean point prevalence of e-cigarette use and use of prescription medication during a quit attempt, the mean point prevalence of successful quit attempts increased by 0.106% (95% CI = 0.011–0.201, P = 0.029) and 0.143% (95% CI = 0.009–0.279, P = 0.038), respectively. For every 1% increase in the mean expenditure on tobacco control mass media, the mean point prevalence of successful quit attempts increased by 0.046% (95% CI = 0.001–0.092, P = 0.046). Other associations were not statistically significant. Conclusion: In England between 2007 and 2018, licensing of nicotine replacement therapy for use in harm reduction, greater use of e-cigarettes and prescription medications during a quit attempt and higher expenditure on tobacco control mass media were all associated with higher success rates of quit attempts.