The effectiveness of varenicline versus nicotine replacement therapy on long-term smoking cessation in primary care: a prospective cohort study of electronic medical records

Background: There is limited evidence about the effectiveness of varenicline and nicotine replacement therapy (NRT) for long term smoking cessation in primary care, and whether the treatment effectiveness differs by socioeconomic position (SEP). Therefore, we estimated the long-term effectiveness of varenicline versus NRT (>2-years) on smoking cessation, and investigated whether effectiveness differs by SEP.  Method: A prospective cohort study of electronic medical records from 654 general practices in England, within the Clinical Practice Research Datalink, using three different analytic methods: multivariable logistic regression, propensity score matching, and instrumental variable analyses (ID:NCT02681848). Exposure was prescription of varenicline versus NRT, and the primary outcome was smoking cessation at 2-years follow-up; outcome was also assessed at 3-,6-, and 9-months, and at 1- and 4-years after exposure. SEP was defined using the Index of Multiple Deprivation.  Results: At 2-years, 28.8% (N=20,362/70,610) of participants prescribed varenicline and 24.3% (N=36,268/149,526) of those prescribed NRT quit; adjusted odds-ratio was 1.26 (95%CI: 1.23 to 1.29), p<0.0001. The association persisted up to 4-years and was consistent across all analyses. We found little evidence that the effectiveness of varenicline differed greatly by SEP. However, patients from areas of higher deprivation were less likely to be prescribed varenicline, adjusted odds-ratio was 0.91(95%CI: 0.90 to 0.92), p<0.0001.  Conclusions: Patients prescribed varenicline were more likely to be abstinent up to 4-years after first prescription than those prescribed NRT. In combination with other evidence, the results from this study may be used to update clinical guidelines on the use of varenicline for smoking cessation.