Is "stage of change" a valid concept ? Jean-François E T T E R Institute of Social and Preventive Medicine, University of Geneva, Switzerland Contact: J.-F. Etter, IMSP,CMU,case postale, CH-1211 Genève 4, Suisse, firstname.lastname@example.org. Tél. +41.22.702.59.19.
Background • The concept of "Stage of change" is widely used by researchers and clinicians. • Is it valid ? • Several "staging" questionnaires are available, do they produce similar results ?
Methods • Setting and participants:- Survey on Internet in 1025 ever smokers, - Retest after 8 days in 318 people (31%), - Follow-up after 32 days in 451 people (44%). • Three different questionnaires assessing "stages of change" based on the same definition of stages:1- http://www.uri.edu/research/cprc/Measures/Smoking11.htm2- Velicer et al. An expert system intervention for smoking cessation. Addict Behav 1993;18:269-290.3- Questionnaire developed by ourselves.
Results • 83 - 93% of participants were classified in the same stage by all questionnaires. • This result calls for a more precise definition of stages and for the use of a unique standardized questionnaire. • 15 - 24% participants were NOT classified in the same stage at 8-day retest:- reflects true movements across the stages ? - or unreliability of the questionnaires ? • 4 - 9% Precontemplators and Contemplators had quit after 32 days: did they skipped intermediary stages?
Results • "Stage of change" includes 4 distinct variables:- intention (stages 1 - 3)- past behavior (stage 3)- current behavior (stages 1 - 5)- duration of current behavior (stages 4 - 5) • None of these 4 variables is measured comprehensively. • Two of these variables (intention and duration) are continuous variables categorized by arbitrary cutpoints.
Intention • Assessed only in current smokers, but intention may also be relevant in ex-smokers. • Cutpoints are arbitrary (1 and 6 months), and may not be the best possible. • Heterogenous categories:- 33 - 38% Precontemplators had "absolutely no intention" of quitting smoking, - 49 - 57% Preparators had made a "firm decision" to quit. • Intention better measured as a continuous variable ?In this study, a 0-10 score of intention to quit was linearly associated with cessation at follow-up.
Current behavior • Dichotomy: smoker (stages 1-3) or ex-smoker (stages 4+5). • "Stage" ignores occasional smoking. • Action stage included 5-7% of occasional smokers, this is contrary to theory, which states that to be classified in the Action stage "only total abstinence counts". • The definition of stages is not based on the WHO conventional definition of ever smokers (>100 cigarettes in a lifetime), which limits the comparability of studies.
Past quit attempts • Used only to identify "Preparators". • Quit attempts also relevant in Precont. and Contempl. • 18 - 24% downgraded to Contemplation because they had not made a quit attempt in the previous year. • The "Contemplation" stage is a heterogenous category:- intention 6 months, with or without quit attempts, and- intention 30 days, without quit attempt. • Smokers can never be "prepared" for their 1st quit attempt. • Test-retest : self-report of 24-hour quit attempts in previous 12 months were unreliable in 12% participants.
Past quit attempts • Quit attempts in previous 7 days or 30 days were better predictors of smoking cessation than quit attempts in the past 12 months (memory bias ?) • Quit attempt of 24 hours: = relatively insignificant events, not well remembered,= short, unsuccessful quit attempts • Once a quit attempt is made, cessation is predicted by variables not in this model: - level of dependence, withdrawal symptoms,- number and duration of past quit attempt, - use of pharmacotherapy.
Time since quitting • Continuous variable categorized by an arbitrary cutpoint. • Enter "Maintenance" stage even when no change occurs. • Also relevant:- number of years as a smoker,- duration of longest quit attempt, • This theory says nothing about: - how long smokers stay in each of the first 3 stages, and- when they progress to the next stage. • Thus stages are not "periods of time" and the TTM is not a model of when people change, contrary to what is often believed.
Conclusions • Measuring independently and comprehensively each of the four variables included in the stage conceptmay provide a more thorough understanding of the process of smoking cessation than using an incomplete mix of these variables.
Acknowledgements • This study was supported by grants from the Swiss National Science Foundation to J.-F. Etter (3233-054994.98 and 3200-055141.98, PROSPER).