Impact of quitline services on tobacco cessation: an application of modern epidemiologic methods.

This study investigated the effectiveness of quitline service intensity (high vs low) on past 30-day tobacco abstinence at 7-months' follow-up, using observational data from the Oklahoma Tobacco Helpline (OTH) between April 2020 and December 2021. To assess the impact of loss to follow-up and nonrandom treatment assignment, we fit the parameters of a marginal structural model to estimate inverse probability weights for censoring (IPCW), treatment (IPTW), and combined (IPCTW). The risk ratio (RR) was estimated using modified Poisson regression with robust variance estimator. Of the 4695 individuals included in the study, 64% received high-intensity cessation services, and 53% were lost to follow-up. Using the conventional complete case analysis (responders only), high-intensity cessation services were associated with abstinence (RR = 1.18; 95% CI, 1.04-1.34). The effect estimate was attenuated after accounting for censoring (RR = 1.14; 95% CI, 1.00-1.30). After adjusting for both baseline confounding and selection bias via IPTCW, high-intensity cessation services were associated with 1.23 times (95% CI, 1.08-1.41) the probability of abstinence compared to low-intensity services. Despite relatively high loss to follow-up, accounting for selection bias and confounding did not notably impact quit rates or the relationship between intensity of quitline services and tobacco cessation among OTH participants.