Cost-effectiveness of motivational interviewing for smoking cessation and relapse prevention among low-income pregnant women: a randomized controlled trial.

OBJECTIVES: Low-income women have high rates of smoking during pregnancy, but little is known about the costs, benefits, and cost-effectiveness of motivational interviewing (MI), focused on the medical and psychosocial needs of this population, as an intervention for smoking cessation and relapse prevention.

METHODS: A sample of 302 low-income pregnant women was recruited from multiple obstetrical sites in the Boston metropolitan area into a randomized controlled trial of a motivational intervention for smoking cessation and relapse prevention versus usual care (UC). The findings of this clinical trial were used to estimate the costs, benefits, and cost-effectiveness of the intervention from a societal perspective, incorporating published quality-adjusted life-year (QALY) and life-year (LY) estimates. Outcomes included smoking cessation and relapse, maternal and infant outcomes, economic costs, LYs and QALYs saved, and incremental cost-effectiveness ratios.

RESULTS: The cost-effectiveness of MI for relapse prevention compared to UC was estimated to be $851/LY saved and $628/QALY saved. Including savings in maternal medical costs in sensitivity analyses resulted in cost savings for MI for relapse prevention compared to UC. For smoking cessation, MI cost more but did not provide additional benefit compared to UC. In one-way sensitivity analyses, the incremental cost-effectiveness of MI versus UC would have been $117,100/LY saved and $86,300/QALY saved if 8% of smokers had quit. In two-way sensitivity analyses, MI was still relatively cost-effective for relapse prevention ($17,300/QALY saved) even if it cost as much as $2000/participant and was less effective. For smoking cessation, however, a higher level of effectiveness (9/110) and higher cost ($400/participant) resulted in higher incremental cost-effectiveness ratios ($112,000/QALY).

CONCLUSIONS: Among low-income pregnant women, MI helps prevent relapse at relatively low cost, and may be cost-saving when net medical cost savings are considered. For smoking cessation, MI cost more but provided no additional benefit compared to UC, but might offer benefits at costs comparable to other clinical preventive interventions if 8-10% of smokers are induced to quit.