QALYs saved (intervention) - QALYs saved (CC)

 
Sensitivity Analysis
To test the robustness of the results, the following parameters were varied: costs of generic medications, biochemically validated tobacco abstinence, actual rates of tobacco abstinence for each gender and age group (for groups larger than 5), and life-years saved (not adjusted for quality of life). Further, because this study used data that were collected in 2003, we performed an additional sensitivity analysis by estimating all costs in 2011 US dollars and using generic medications when available to determine current cost-effectiveness implications. Finally, a subgroup analysis was conducted using smokers who did not want to stop within 30 days (n = 370).

RESULTS
Descriptive Statistics at Baseline
Table 2 presents descriptive statistics at baseline for the 737 insured smokers across the 2 conditions. There were no statistically significant group differences in the baseline variables or percentage of participants who were lost to follow-up at 6 months.

7dPP Tobacco Abstinence at 6 Months
Table 3 presents the total number and percentage of smokers who attained 7dPP tobacco abstinence at 6 months across the 2 conditions. Participants in the intervention, relative to the CC group, were more likely to attain both self-reported (15.59% vs 4.74%; χ² (1) = 16.23, P <.01) and biochemically validated (12.74% vs 3.32%; χ² (1) =  14.79, P <.01) measures of 7dPP tobacco abstinence at 6 months. Among those who did not want to stop smoking within 30 days, participants in the intervention, relative to the CC group, were more likely to attain self-reported 7dPP tobacco abstinence at 6 months (13.79% vs 4.59%; χ² (1) = 6.61, P <.05).

Incremental Costs per Participant and Incremental Cost-effectiveness Ratios
Total study costs averaged $145 per participant in the CC group and $377 per participant in the intervention group (this difference was due to higher variable costs in the intervention). The incremental costs per participant in the intervention ranged from $161 to $432. The overall incremental cost-effectiveness ratio, discounted at 3%, was $1258 per QALY, and ranged from $645 to $2674 per QALY. Examination of the gender and age breakdown showed that the cost-effectiveness ratios were slightly better (ie, lower ratio) for younger men. The incremental cost-effectiveness ratio, discounted at 3%, for the subgroup who did not want to stop within 30 days at baseline was $1242 per QALY, and ranged from $586 to $3828 per QALY.

Sensitivity Analyses
Sensitivity analyses confirmed the robustness of our findings. By changing all medication costs from brand name to generic, the overall incremental cost-effectiveness ratio was reduced by about 10% to $1144 per QALY, and ranged from $699 to $2616 per QALY. By classifying only those with biochemically validated 7dPP as having attained tobacco abstinence, the overall incremental cost-effectiveness ratio was increased by about 34% to $1692 per QALY, and ranged from $749 to $5668 per QALY. By using actual rates of tobacco abstinence for each gender and age group, the overall incremental cost-effectiveness ratio was increased by about 1% to $1267 per QALY, and ranged from $542 to $2670 per QALY. By using life-years saved (not adjusted for quality of life), the overall incremental cost-effectiveness ratio was $498 per life-year saved, and ranged from $294 to $2343 per life-year saved. By estimating all costs in 2011 US dollars, the overall incremental cost-effectiveness ratio was increased by about 6% to $1332 per QALY, and ranged from $814 to $3047 per QALY.

DISCUSSION
An intensive tobacco dependence intervention based on SDT that targeted all smokers, not only those who wanted to stop within 30 days, was found to be cost-effective compared with other services commonly covered by health plans, including less intensive tobacco dependence treatment and prevention, as well as other medical services. Remarkably, the overall incremental cost-effectiveness ratio was about $1300 per QALY. Indeed, these findings were based on intention-totreat data and thus may be conservative estimates. Further, unlike in actual practice, all CC participants in this study were offered a low-intensity intervention. Sensitivity analyses indicated that using: (1) generic medications, (2) biochemically validated tobacco abstinence, (3) actual rates of tobacco abstinence for each gender and age group, (4) life-years saved (not adjusted for quality of life), and (5) costs in 2011 US dollars yielded only small changes in cost per QALY, suggesting that our findings were robust to several plausible variations in the model parameters.
 
These findings support adoption of intensive tobacco dependence interventions by the US healthcare system for all smokers who are willing to discuss their tobacco use, as the SDT-based intervention was cost-effective even for those who did not want to stop within 30 days. Although the intervention was provided by a tobacco dependence treatment team, it was integrated with cardiovascular risk information typically discussed in primary care settings, and about half of the participants who used medications received them from their own healthcare provider. Thus, it is feasible for primary care providers to deliver the intervention to smokers who are willing to receive intensive treatment, although we note that within the scope of this study we were not able to measure all costs associated with this form of delivery. Alternatively, a healthcare system could employ counselors at a central location with which primary care providers could collaborate to provide the intervention.
 
Herein, and in other published articles from this trial, we have emphasized the importance of demonstrating that theoretically consistent mechanisms of change explain the effect of the intervention in facilitating long-term tobacco abstinence. Previous findings from this trial have shown that the intervention was effective in enhancing patient autonomy and perceived competence, and thus consistent with the SDT model of health-behavior change.¹⁴ Interventions, no matter how intensive, that do not address these fundamental aspects of motivation may not yield comparable cost-effectiveness estimates. The proposed explanatory constructs derived from SDT—autonomy and perceived competence—are wholly consistent with the principles of biomedical ethics. Although a focus on mediators of treatment effects is relatively rare among cost-effective interventions, its importance is not to be missed. For instance, if the intervention facilitated tobacco abstinence but undermined patient autonomy, it would not be suitable for translation into medical practice because support for patient autonomy is an outcome that is equivalent to improving patient well-being.^15,25 That cost-effective interventions support patient autonomy ought to be a benchmark standard for future comparative effectiveness trials and value-based medical studies to attain.²⁶
 
Several limitations deserve mention. First, the generalizability of our findings may be limited, as they were based on a single study with a modest sample size and participants who were recruited only from the greater Rochester, New York area. Second, medication costs were based on the self reported amount of medication purchased, as we did not have the amount of medication consumed by each participant, and cost estimates for medications were obtained from the largest private insurer in the greater Rochester, New York, area. Third, we did not estimate the specific QALYs for our participants, but instead used published estimates of the effects of smoking cessation on quality of life and life expectancy within a nationally representative US sample stratified by gender and age.²⁴ The full benefits of smoking cessation take many years to accrue and thus could not be directly derived from our study sample. Indeed, a recent study has demonstrated the improvement in quality of life for non-smokers and those who have stopped relative to those still smoking.²⁷ Fourth, all participants who were lost to follow-up were assumed to be smoking, but this approach yields more, rather than less, conservative estimates, and modifications of relevant model parameters produced similar findings, thus underscoring the robustness of our findings. Future studies might focus on other areas of health-behavior change and evaluate cost-effectiveness based on QALYs for study participants.

Take-Away Points

This study evaluated cost-effectiveness of an intensive tobacco dependence intervention based on self-determination theory and consistent with the Public Health Service-sponsored Clinical Practice Guideline for Treating Tobacco Use and Dependence.

• Findings suggested that the intervention was highly cost-effective (about $1300 per quality-adjusted life-year in US dollars) among insured smokers, both for those who did and did not want to stop smoking within 30 days.

• Sensitivity analyses indicated little variation in cost-effectiveness using generic medications, biochemically validated tobacco abstinence, actual rates of tobacco abstinence for each gender and age group, life-years saved (not adjusted for quality of life), and costs in 2011 US dollars.

Affiliation

Author Affiliations: From School of Nursing (IP-K), Healthy Living Center (GCW), Department of Clinical and Social Sciences in Psychology (CPN), School of Medicine and Dentistry (KF), University of Rochester, Rochester, NY.

Funding Source: This research was supported by grants R01-CA106668 from the National Cancer Institute and by R01-MH59594 which was cofunded by the National Institute of Mental Health and the National Cancer Institute. Trial Registration, ClinicalTrials.gov number, NCT00178685.

Author Disclosures: Dr Williams reports that he has received honoraria for consultancies or paid advisory boards from Self-Determined Health and also reports stock ownership. The other authors (IP-K, CPN, KF) report no relationship or financial interest with any entity that would pose a conflict of interest with the subject matter of this article.

Authorship Information: Concept and design (GCW, IP-K, CPN, KF); acquisition of data (GCW, CPN); analysis and interpretation of data (GCW, IP-K, CPN, KF); drafting of the manuscript (GCW, IP-K, CPN, KF); critical revision of the manuscript for important intellectual content (GCW, IP-K, CPN, KF); statistical analysis (IP-K); obtaining funding (GCW); administrative, technical, or logistic support (GCW); and supervision (GCW).

Address correspondence to: Geoffrey C. Williams, MD, PhD, Healthy Living Center, Center for Community Health, University of Rochester, 46 Prince St, Ste 3001, Rochester, NY. E-mail: geoffrey_williams@urmc.rochester.edu.

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