Ineffective, incorrect and unethical:
Where next for the TTM and smoking
cessation research?
Chris Bridle¹
Camille Alexis²
Simon Murphy³
¹Warwick Medical School, University of Warwick
² Department of Primary Care & Population Studies, UCL
³ Institute for Society, Health & Ethics, University of Cardiff
Chris Bridle, PhD, CPsychol
Institute of Clinical Education
Warwick Medical School
University of Warwick
Tel: +44(24) 761 50222
Email: C.Bridle@warwick.ac.uk
www.warwick.ac.uk/go/hpsych
Overview

Background context

TTM and a framework for intervention

Available evidence and its limitations

Solutions for meaningful research

Our ‘meaningful’ research

Interpretation and conclusions
Background

Behaviour influences health



Health influences policy



PCTs funded to deliver smoking cessation services
DoH targets for recruitment and effectiveness
Policy influences practice



25% of UK adults smoke – 12 million people
120,000 smoking-related deaths in Britain pa
Stage-based theories dominant in Primary Care
Transtheoretical Model (TTM)
Evidence influences ... ?
Transtheoretical Model
(Prochaska & DiClemente, 1983)
Experiential +  Processes of Change  + Behavioural
PreCon
Con
Prep
Action
Maint
Stages of Change
Self-Efficacy
Situational
Self-Efficacy
Decisional
Balance
Temptations
Interventions that take account of an individual's stage
Pros
of change will be more effective in promoting behaviour
change than 'one size fits all' interventions
Cons
Available Evidence

Systematic reviews x 4 3½




Stage-based interventions (Riemsma et al. 2002)
TTM interventions for smoking cessation (Spencer et
al. 2002)
Stage-based interventions for smoking cessation
(Riemsma et al. 2003)
TTM interventions (Bridle et al. 2005)
Conclusion
‘Little evidence that stage-based interventions
are more effective than other stage-based
interventions, non-stage-based interventions,
or even usual care’ (Bridle et al. 2005)
'... but Chris, what does that mean?'
It means that three decades of research has failed to
provide an answer to the most important question ...
Does it work?
THE Question

Does the TTM provide a framework for developing
effective health behaviour change interventions?

No: Wrong, ... lack of evidence of effect is not the
same as evidence of lack of effect (Doug Altman, or
someone else who is very clever)


Yes: Wrong, ... lack of good quality evidence
necessarily prohibits meaningful inferences about
effectiveness


Who knows?: Correct, ... we don’t know because
there are important gaps and weaknesses in the
evidence base

Why Gaps and Weaknesses?




Little evidence in an obscure area? 18 RCTs published
in 2+ impact factor journals since Jan 2006
Flaws in the design, conduct and analysis of trials are
repeated consistently – incorrect research
Flawed research contributes nothing meaningful to the
evidence base –ineffective research
Repeated flaws are well recognised and their effects
are well documented – unethical research(ers)
Meaningful research fills gaps and strengthens
areas of weakness
Inconsistent Evidence
Limitation / Explanation
Solution
Content theoretically incorrect
- Fully tailored Vs stage-based
Delivery conceptually incongruent
- Responsive and evolving
Concealed random allocation, etc.
- Good practice guidelines
Biased sampling
- Demotivated demoralised smokers
Too few participants
- a priori sample size calculation
Exposure variable
- Computer-generated feedback
Treatment comparability
- Standardise intervention contact
Exclusion of Ps from analysis
- Include all participants – ITT
Use of surrogate endpoints
- Behavioural - smoking status
Premature assessment
- Long-term effects (6+ months)
Long term effects
Present Study
Stage-based
V's Fully tailored
12-month RCT evaluating the effects of differently
tailored, computer-generated smoking cessation
interventions among hard-to-reach smokers
Tailored but standardised
intervention content
Behavioural
Demotivated &
outcomes
demoralised losers
features participants
that protect internal validity are
Essential design
balanced against the demand for a pragmatic intervention that
has external validity and potential to shape practice patterns
within a large health care system
Key (Meaningful?) Questions





Effectiveness: How effective are stage-based and fully
tailored interventions for promoting smoking cessation?
Theory: Is stage progression predicted by distinct
processes of change and different stages of change?
Practice: Can TTM direct resource allocation by identifying
smokers who are at-risk, unresponsive &/or hard-to-reach?
Process: Do different tailoring levels have different effects
at different stages and for different people?
Research: Can the study bring meaning to the evidence
base by identifying sources of effect heterogeneity?
Expert system / computer programme

Tailored, but standardised content



Message generation for TTM variables and validated by
key stakeholders
Algorithms to combine messages based on TTM scores
and tailored to demographic factors
Pilot evaluation of feedback messages (i.e. intervention
content) using current smokers

Readability: high, non-significant (ns) difference

Personal relevance: moderate, ns difference

7-day recall: significantly higher for fully tailored
Conditions



Stage-based (I1): Partially tailored feedback based
only on the participant’s stage of change
Fully tailored (I2): Feedback tailored to TTM variables
and relevant participant demographic factors
Usual care (C): NHS leaflet 'Giving Up for Life‘, which
contains some stage-based information and advice
LREC insisted we provide our ‘no intervention’ control group
with … erm … an intervention
‘The study benefited
greatly from the insightful
‘Tossers’
guidance provided by the LREC’
Feedback Example: Contemplation
Temporal
Relevance
Stage-based: Stopping smoking
Fully tailored: Stopping smoking
at any age increases life
before you are 30 years old will
expectancy. The benefitsPersonalised
of
increase your life expectancy to
–
stopping begin immediately
the same as someone who has
Self-relevance
blood circulation improves (20
never
Fearsmoked.
Arousal
minutes); blood oxygen levels
Once you stop smoking your
increase to normal (8 hours); the
chances of having a heart attack
body is nicotine-free (48 hours);
begin to fall after only 8 hours,
breathing is easier and energy
and your risk is halved after 5
levels increase (72 hours).
years and, after 10 years, your
Later, circulation improves Response
and
risk is the same as someone who
Efficacy
exercise becomes easier (2-10
has never smoked.
weeks); lung efficiency increases
Stopping smoking halves the risk
by 5-10% (3-6 months); risk of
that your children will be smokers,
having a heart attack is halved (5
and having a non-smoking spouse
years); risk of lung cancer is
doubles your chances of quitting
halved and risk of heart attack is
permanently compared to smokers
the same as someone who has
whose spouse is also a smoker.
Normative
never smoked (10 years).'
beliefs
Social Support
Outcomes

Effectiveness



Primary outcome: Self-reported abstinence defined as
having smoked no more than 5 cigarettes since previous
follow-up (3 months)
Secondary outcomes: 7-day point-prevalence abstinence
(no tobacco use), no. of 24-hour quit attempts, and
stage movement (progression or regression)
Effect mediators


Treatment factors: no. of feedback reports provided, and
uptake and use of co-interventions, e.g. return to NHS
SSS, NRT, non-nicotine pharmacotherapy
Psychological factors: change from baseline in
situational self-efficacy for smoking abstinence, and pros
and cons of behaviour change, i.e. decisional balance
Sample & Sample Size



Adult smokers who failed to quit after starting the NHS
Stop Smoking Service's (SSS) cessation programme
Database of ‘failed quitters’ in 5 PCTs – random selection of
500 from each database limited to previous 12 months
a priori calculation based on predicted difference in
proportions (%) of self-reported abstinence



3, 10 and 20% for C, I1 and I2 respectively
80% power to detect 7% difference at .05 sig. level
(n=220) with an anticipated attrition rate of 25% (n=55)
Sample size required; n=275 per group, i.e. N=825
Design Overview




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Randomised controlled trial with
concealed allocation stratified
by stage of change
Invited to Participate
N=2500
Data collected via mailed
questionnaire at baseline and 3,
6, 9 and 12 months
Randomised N=850 (34%)
PC=122, C=481, P=247
Feedback mailed within 2 weeks
of receiving questionnaire data
Non-response protocol: 2 tel.
attempts + 1 mailed reminder
ITT assessment for treatment
effect using logistic regression
controlling for PCT and SoC
Pre-specified subgroup analysis
for potential moderators and
mediates
C, n=280
I1, n=290
I2, n=280
A
B
C
D
A
B
C
D
A
B
C
D
231
222
210
192
(83%)
(79%)
(75%)
(69%)
257
233
202
191
(87%)
(77%)
(70%)
(66%)
245
231
217
205
(88%)
(82%)
(78%)
(73%)
Participant Characteristics
Conditions
Characteristic (%)
Control
(n=280)
I1: Stage
(n=290)
I2: Full
(n=280)
Mean age, y
49
47
48
Female
62
61
65
British, White
87
84
83
Employed (FT)
75
77
72
Single, live alone
64
63
67
Education (school)
56
58
57
SES (low 4-5)
63
65
62
Baseline TTM Variables X SoC
Variable
(mean ± SD)
PreCont.
n=122, 14%
Cont.
n=481, 57%
Prep.
n=247, 29%
Dependency

5.5 ± 2.1
5.3 ± 2.3
4.6 ± 2.2
Self-Efficacy
?
15.6 ± 4.6
19.3 ± 6.2
19.8 ± 6.7
Decisional Balance 
-2.3 ± 3.2
0.6 ± 3.3
2.1 ± 3.2
PoC Behavioural

18.3 ± 5.4
22.7 ± 6.1
25.6 ± 7.3
PoC Experiential

26.7 ± 7.5
31.2 ± 7.1
33.3 ± 7.5
Effectiveness Outcomes
Primary and secondary outcomes as proportions (%)
Control
Stage-Based
Fully Tailored
Outcome
3
6
9
12
3
6
9
12
3
6
9
12
P-Abs¹
9
7
5
4
16
10
8
5
6
11
14
12
7-Abs
11
7
6
7
26
10
5
5
12
15
17
12
24-Quit
18
11
8
5
29
22
11
7
16
9
10
8
Stage +
18
10
5
2
17
11
6
4
33
27
23
14
Stage -
16
12
8
5
17
17
10
16
10
6
4
4
¹Accululative data – all other data represent new cases
Effect Estimates
Odds of being a non-smoker at 3, 6, 9 and 12 months
Contrast: OR (95% CI)
Follow-up
I1 (C)
I2 (C)
I2 (I1)
3 months
1.79 (1.06, 3.03)
1.51 (0.79, 2.88)
0.36 (0.21, 0.65)¹
6 months
1.18 (0.67, 2.09)
1.41 (0.79, 2.51)
1.08 (0.63, 1.86)
9 months
1.56 (0.81, 2.98)
3.08 (1.69, 3.59)
1.98 (1.17, 3.33)
12 months
1.04 (0.48, 2.26)
3.89 (1.81, 8.31)
2.54 (1.33, 4.88)
¹I1(I2): OR 2.77 (1.54, 4.98)
Conclusions





Stage-based intervention is significantly more effective
than both usual care and fully tailored intervention in shortterm - 3 months
In the longterm stage-based intervention is no more
effective than Usual Care and significantly less effective
than fully tailored intervention
Short-term evaluation of stage-based intervention may
overestimate positive effects and underestimate, or miss,
longer term adverse consequences
Fully tailored intervention significantly more effective in
promoting long-term behaviour change and stage
progression, i.e. 6+ months
Beneficial effects of fully tailored intervention evident only
in long-term assessment
Where, or What Next?




Research moratorium: Periodic cessation of research and
evidence assessment to guide more meaningful research
Methods reporting / quality: Supplement CONSORT with
guidelines for reporting intervention content
Mechanisms of action (MoA): Identify active ingredients
to maximise clinical and cost-effectiveness
Effect assumption: Habitual behaviours are not driven by
attitudes and beliefs, but by contextual cues to action


Intervention is effective for 50% of people 100% of the
time – focus on antecedent attitudes and belief 
Intervention is effective for 100% of people 50% of the
time – focus on concurrent context of change 
Thank you.
Any questions … now or later?
Chris Bridle, PhD, CPsychol
Institute of Clinical Education
Warwick Medical School
University of Warwick
Tel: +44(24) 761 50222
Email: C.Bridle@warwick.ac.uk
Web: www.warwick.ac.uk/go/chrisbridle