Abstinence from smoking was defined as a self-report of nonsmoking for the previous 7 days and was considered to be biochemically confirmed with an expired air carbon monoxide value below eight parts per million (ppm). If the participant failed either of these two conditions (reported any smoking in the previous 7 days or had a CO greater than 8 ppm) then the participant was categorized as a smoker. In order to produce a conservative estimate of smoking abstinence, study outcome data were analyzed in an intent-to-treat model. If a participant failed to complete a visit for whatever reason (missed a visit or terminated early from the study), the participant was classified as a smoker for that incomplete visit.
