Predictive validity of the Motivation To Stop Scale (MTSS): A single-item measure of motivation to stop smoking

Background: Many different measures of motivation to stop smoking exist but it would be desirable to have a brief version that is standard for use in population surveys and for evaluations of interventions to promote cessation. The aim of this study was to assess the predictive validity and accuracy of the single-item Motivation To Stop Scale (MTSS). Methods: This study is part of the "Smoking Toolkit Study;" a monthly survey of representative samples of the English population. We used data from 2483 respondents to the surveys from November 2008 to January 2011, who were smokers, used the MTSS, and were followed up 6 months later to provide information on quit attempts since baseline. The MTSS consists of one item with seven response categories ranging from 1 (lowest) to level 7 (highest level of motivation to stop smoking). Results: A total of 692 smokers (27.9% (95% CI = 26.1-29.6)) made an attempt to quit smoking between baseline and 6-month follow-up. The odds of quit attempts increased linearly with increasing level of motivation at baseline (p <0.001) and were 6.8 (95% CI = 4.7-9.9) times higher for the highest level of motivation compared with the lowest. The accuracy of the MTSS for discriminating between smokers who did and did not attempt to quit was ROCAUC =0.67 (95% CI = 0.65-0.70). Conclusions: The MTSS provides strong and accurate prediction of quit attempts and is a candidate for a standard single-item measure of motivation to stop smoking. Further research should assess the external validity of this measure in different smoking populations.