It is not known how well motivation to stop smoking predicts abstinence in a clinical sample relative to the most widely used measure of cigarette dependence.
A secondary analysis was conducted from a trial with 864 smokers making quit attempt. Fagerström Test of Cigarette Dependence (FTCD), Heaviness of Smoking Index (HSI), and motivation to stop smoking (composite of determination to quit and importance of quitting) were measured at baseline. Continuous smoking abstinence, validated by expired-air carbon monoxide, was assessed at 4 weeks, 6 months and 12 months post-quit date. FTCD, HSI, non-HSI items in FTCD, and motivation were assessed as predictors of abstinence.
In multiple-logistic regressions, controlling for age, gender and medication use, lower scores for FTCD, HSI and non-HSI all significantly predicted abstinence at all follow-ups, while motivation did not predict abstinence at any time. Likelihood ratio tests showed that the FTCD contributed most to the model at 4 weeks and 6 months; at 12 months FTCD and non-HSI equally contributed most to the model. At 4 weeks and 6 months, predictions were improved by combining HSI and non-HSI components, compared with using these components alone.
Cigarette dependence, measured by the FTCD, or by its HSI or non-HSI components, predicts both short-term and medium-term outcomes of attempts to stop smoking in treatment-seeking smokers involved in a clinical trial, whereas strength of motivation to stop predicts neither. Both the HSI and non-HSI components may be considered as briefer alternatives to the full FTCD.