Effectiveness of motivational interviewing, health education and brief advice in a population of smokers who are not ready to quit

Abstract

Background: Motivational Interviewing (MI), Brief Advice (BA) and Health Education (HE) are established smoking cessation induction methods for smokers with low desire to quit. Although randomized controlled trials (RCT's) have been frequently used to assess these interventions the temporal efficacy and effectiveness of these interventions have been poorly elaborated. The present work endeavors to fill the gap by considering the full range of possible motivational outcomes for all of the participants.

Methods: As a two-step process, Markov Chain (MC) and Ordinary Differential Equation (ODE) models were successively employed to examine the temporal efficacy and effectiveness of these interventions by computing the gradual movements of participants from an initial stage of unmotivated smoker to stages of increased motivation to quit and cessation. Specifically, in our re-analysis of data from the RCT we examined the proportion of participants in 4 stages of readiness to quit (unmotivated, undecided, motivated, former smokers) over 6 months, across treatment groups [MI (n = 87), BA (n = 43) and HE (n = 91)].

Results: Although HE had greater efficacy compared to MI and BA (i.e., the highest smoking cessation rates), it had lower effectiveness at certain time points. This was due to the fact that HE had the greatest proportion of motivated smokers who quit smoking but simultaneously a large proportion of the motivated smokers became unmotivated to quit. The effectiveness of HE dropped substantially in weeks 3-12 and remained below the effectiveness of BA from week 12 onward. The 2-year ODE model projections show that the prevalence of motivated smokers in HE group may fall below 5%. The prevalence of HE former smokers can reach an equilibrium of 26%, where the prevalence of both BA and MI former smokers exceeds this equilibrium.

Conclusions: The methodology proposed in this paper strongly benefits from the capabilities of both MC and ODE modeling approaches, in the event of low observations over the time. Particularly, the temporal population sizes are first estimated by the MC model. Then they are used to parametrize the ODE model and predict future values. The methodology enabes us to determine and compare the temporal efficacy and effectiveness of smoking cessation interventions, yielding predictive and analytic insights related to temporal characteristics and capabilities of these interventions during the study period and beyond.

Trial registration: Testing Counseling Styles to Motivate Smokers to Quit, NCT01188018 , (July 4, 2012). This study is registered at www.clinicaltrials.gov NCT01188018.

Keywords: Brief advice; Effectiveness; Efficacy; Health education; Markov chain model; Motivational interviewing; Smoking cessation.

Fig. 1

The compartmental diagram of quit progression among smokers who are not ready to quit. The self-assessment data was used to determine the stages of smokers. The arrows show the possible transitions between the stages. Note that the last stage is the 7-day point-prevalence smoking abstinence, which is an absorbing state. The parameters d_ij, denote the rate of transition from stage i to stage j with i,j = 1,…,4;i ≠ j

Fig. 2

Estimated 26-weeks prevalence using the MC model. b BA participants had a higher prevalence of indecisive smokers. d Although HE was more effective than MI and BA, HE participants substantially lost their motivations (c), many of whom became fully unmotivated (a)

Fig. 3

Relative efficacy and effectiveness of BA, HE and MI, a The efficacy of HE was superior to BA and MI throughout the study. b The effectiveness of HE dropped drastically in weeks 3–12 and it remained below the effectiveness of BA from week 12 onward. A penalty of α = 0.20 was considered in the effectiveness formula (3)

Fig. 4

Estimated transition probabilities into the final stage (Former Smoker). a Indecisive smokers in HE group had a higher probability to quit. b The motivated smokers in the MI group had an overall higher transition probability until week 17

Fig. 5

Prevalence of smoker populations projected over 2 years. a The prevalence of unmotivated HE participants kept growing and exceeded 60%. b There was a sharp decline in the prevalence of indecisive smokers in all three groups. c The motivated smokers in HE group reached below 5%. d The prevalence of BA former smokers exceeded 45%