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

Abstract

Background: There is limited evidence about the effectiveness of varenicline and nicotine replacement therapy (NRT) for long-term smoking cessation in primary care, or 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.

Methods: This is a prospective cohort study of electronic medical records from 654 general practices in England, within the Clinical Practice Research Datalink, using three different analytical methods: multivariable logistic regression, propensity score matching and instrumental variable analyses. 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% confidence interval (CI): 1.23 to 1.29], P < 0.0001. The association persisted for 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.

Keywords: Smoking cessation; causal; cohort; effectiveness; electronic medical records; instrumental variable; nicotine replacement therapy; primary care; tobacco; varenicline.

Figure 1

Absolute quit rates by treatment group at 3, 6 and 9 months and 1, 2 and 4 years after exposure, N = 220 136.

Figure 2

The association of prescribing varenicline and smoking cessation at 3,6 and 9 months and 1, 2 and 4 years after first prescription. Fully multivariable adjusted logistic regression model: odds ratio and 95% confidence intervals presented. The difference in smoking cessation rates peaks at 6 months and declines over the following 3.5 years, N = 220 136.

Figure 3

The effectiveness of varenicline stratified by socioeconomic position. Partial adjusted odds ratios and 95% confidence intervals for the association of prescription of varenicline versus NRT and smoking cessation at 3, 6 and 9 months and 1, 2 and 4 years after exposure, by level of deprivation as measured by the Index of Multiple Deprivation Score (IMD). IMD is an increasing measure of neighbourhood disadvantage; models were adjusted for age, sex and year of first prescription. Missing IMD values were not imputed and patients with missing IMD data were excluded from all analyses, to ensure comparability of results across samples. Legend: □ Patients from least deprived areas (IMD scores 1 to 10), N = 52 534. ▴ Patients from most deprived areas (IMD scores 11 to 20), N = 72 247.

Figure 4

Random effects meta-analysis comparing effect estimates (odds ratio and 95% confidence interval) from existing studies examining the effect of varenicline versus NRT for smoking cessation at 6–12 months’ follow–up.