The sample

size for this analysis was lower because the 3-month follow-up was only included for some waves of the study. The sample followed up 6 months after baseline (N = 2483) differed only slightly from those not followed up (N = 9180) in being more likely to be female and older, to have slightly higher strengths of urges to smoke, HSI score and daily cigarette consumption, and being less motivated to stop ( Table 1). Although small, all the differences were statistically significant. Fig. 1 shows the distribution of scores on the MTSS at baseline in the follow-up sample (N = 2483). The two most frequently stated levels of motivation were level 1: “I don’t want to stop smoking” (20.7%) and level 4: “I REALLY PD-1/PD-L1 inhibitor review want to

stop smoking but I don’t know when I will” (23.8%). Eighteen percent of smokers (N = 447) scored the two highest levels of motivation: “I REALLY want to stop smoking and intend to in the next 3 months” or “…in the next month” (95% CI = 16.5–19.5%). A total BKM120 chemical structure of 692 smokers (27.9% (95% CI = 26.1–29.6)) made an attempt to quit smoking between baseline and 6-month follow-up. Fig. 2 presents the percentage of smokers attempting to quit stratified by their baseline MTSS score. The figure shows a linear increase in the percentage making quit attempts with increasing level of motivation (χ2 = 193.408, df = 6, p < 0.001 for a linear-by-linear association). Of the 447 smokers who scored the two highest levels of motivation, 219 made an attempt

to quit (positive predictive value = 49%). The odds of making a quit attempt between baseline and 6-month follow-up according to the MTSS score are presented Urease in Table 2. Smokers with the highest score had 6.8 times the odds of making a quit attempt (95% CI = 4.7–9.9) than smokers with the lowest score. The odds ratios were similar after adjusting for age, sex, social grade, strengths of urges to smoke, HSI, cigarettes smoked per day at baseline, and wave of the survey (Table 2). Fig. 3 shows the ROC curve for our measure of motivation. The ROCAUC was 0.67 (95% CI = 0.65–0.70). The ROCAUCs of the two variables used to assess the divergent validity were 0.47 (95% CI = 0.45–0.50) for HSI and 0.53 (95% CI = 0.50–0.55) for strengths of urges to smoke (Supplementary Fig. E1).1 A total of 1842 respondents were included in the sensitivity analysis, of which 388 (21.3%, 95% CI = 19.4–23.3) made an attempt to quit smoking between baseline and 3-month follow-up. The odds of making a quit attempt over that period according to the MTSS score differed from the odds over the period between baseline and 6-month follow-up, particularly for the highest MTSS score (Supplementary Table E1)1. Smokers with the highest score had 9.2 times the odds of making a quit attempt within the next 3 months (95% CI = 5.62–15.08).