Tobacco Control Interventions – Tobacco Control Interventions – Design Trade-OffsDesign Trade-Offs

K. S. (Steve) BrownK. S. (Steve) Brown

Department of Statistics and Actuarial ScienceDepartment of Statistics and Actuarial Science

Health Behaviour Research GroupHealth Behaviour Research Group

University of WaterlooUniversity of Waterloo

What is the Intervention?What is the Intervention?

ComprehensiveComprehensive mix mix of policies and programs is of policies and programs is thought to be most effective way to reduce tobacco thought to be most effective way to reduce tobacco use with youth (CDCP, 1999).use with youth (CDCP, 1999).

Some evidence that school-based programs work Some evidence that school-based programs work best in conjunction with other efforts (e.g. with best in conjunction with other efforts (e.g. with media activities, by-laws or part of community-wide media activities, by-laws or part of community-wide intervention)intervention)..

e.g. Florida e.g. Florida state-widestate-wide intervention emphasized intervention emphasized youth leadership in planning and implementing youth leadership in planning and implementing interventions in schools and communities.interventions in schools and communities.

Unlike Trials of Therapeutic Unlike Trials of Therapeutic Agents…..Agents…..

Many of the tenets of RCT’s do not carry over to Many of the tenets of RCT’s do not carry over to community trialscommunity trials

““Intervention” is more than just the agent (e.g. Intervention” is more than just the agent (e.g. program or policy), but must include provider, program or policy), but must include provider, setting and contextsetting and context

Hard – and not realistic – to try to control these Hard – and not realistic – to try to control these factors (e.g. provider, setting, context)factors (e.g. provider, setting, context)

Intervention IssuesIntervention Issues

• Multi-faceted mix of programs and policiesMulti-faceted mix of programs and policies• Interventions in many settings (schools, Interventions in many settings (schools,

stores, media, political jurisdictions)stores, media, political jurisdictions)• Interventions need “champion(s)” at the Interventions need “champion(s)” at the

local levellocal level• Communities need to be ready to interveneCommunities need to be ready to intervene• Sustainability of interventions after the Sustainability of interventions after the

research team leaves is an issueresearch team leaves is an issue

Intervention IssuesIntervention Issues

• Randomized TrialRandomized Trial – communities could – communities could pick from menu, but implement several pick from menu, but implement several activities simultaneously activities simultaneously

• Communities must be ready to intervene in Communities must be ready to intervene in more than one areamore than one area

• Hard to attribute “success” to individual Hard to attribute “success” to individual componentscomponents

Intervention IssuesIntervention Issues

• Multiple BaselineMultiple Baseline – interventions implemented – interventions implemented one-at-a-time in different settingsone-at-a-time in different settings

• Might be more feasible to have communities Might be more feasible to have communities tackle only one interventiontackle only one intervention

• Assumes effects are additive – dangerous if Assumes effects are additive – dangerous if interactions are presentinteractions are present

• Some programs may not work in isolation but may Some programs may not work in isolation but may act synergistically with other componentsact synergistically with other components

Methodological IssuesMethodological Issues

End-PointsEnd-Points Measures of Smoking, Process variablesMeasures of Smoking, Process variables Inclusion/Exclusion Criteria Inclusion/Exclusion Criteria Blocking/StratificationBlocking/Stratification Randomization (?)Randomization (?) BlindingBlinding Duration of the studyDuration of the study Longitudinal vs. Repeated Cross-SectionalLongitudinal vs. Repeated Cross-Sectional

Intermediate (Surrogate) End-PointsIntermediate (Surrogate) End-Points

Knowledge, beliefs, values, attitudes, intentionsKnowledge, beliefs, values, attitudes, intentions

ExperimentationExperimentation

Regular Smoking (Weekly Daily)Regular Smoking (Weekly Daily)

Regular Smoking (Adult)Regular Smoking (Adult)

Disease and DeathDisease and Death

Process End - PointsProcess End - Points

Process variables must be measured to Process variables must be measured to assess intervention componentsassess intervention components

RCT Design assess process and smoking RCT Design assess process and smoking data simultaneouslydata simultaneously

Multiple Baseline Design intervenes in Multiple Baseline Design intervenes in stages. Not all communities need to stages. Not all communities need to measure both process and smoking datameasure both process and smoking data

Measures of Smoking, Process Measures of Smoking, Process VariablesVariables

• Smoking measures depend on self-reportSmoking measures depend on self-report• Measures of process are essential to monitor Measures of process are essential to monitor

community activitycommunity activity• Requires measurement of all facets of Requires measurement of all facets of

intervention (e.g. restrictions on sales, intervention (e.g. restrictions on sales, enforcement of by-laws, etc.)enforcement of by-laws, etc.)

Measures of Setting and Context Measures of Setting and Context FactorsFactors

Need to find reliable measurement systems for Need to find reliable measurement systems for setting and contextual factors such as setting and contextual factors such as programs, policies and broader environmental programs, policies and broader environmental variablesvariables

Need commitment from communities to Need commitment from communities to continually monitorcontinually monitor

Interesting analysis challenges with variables Interesting analysis challenges with variables at level of student, school, community, and at level of student, school, community, and larger jurisdictionslarger jurisdictions

Inclusion/ExclusionInclusion/Exclusion

Inclusion/exclusion criteria are based on Inclusion/exclusion criteria are based on community characteristicscommunity characteristics

Subjects are indirectly recruitedSubjects are indirectly recruited Purpose of research/benefits of research not Purpose of research/benefits of research not

necessarily a priority for the community necessarily a priority for the community Need willing champions in the communities Need willing champions in the communities

and researchers willing to work in and researchers willing to work in communitiescommunities

Blocking/StratificationBlocking/Stratification

Matched pairs RCT requires communities Matched pairs RCT requires communities to be matched on characteristics related to to be matched on characteristics related to outcome (e.g. adult smoking rates, SES, outcome (e.g. adult smoking rates, SES, etc.)etc.)

Community pairs should include wide Community pairs should include wide variation in expected outcome for variation in expected outcome for generalizability.generalizability.

Could include pairs in different countriesCould include pairs in different countries

Blocking/StratificationBlocking/Stratification

Multiple Baseline design uses each Multiple Baseline design uses each community as its own control and corrects community as its own control and corrects for secular effects with staggered startfor secular effects with staggered start

Fewer communities in each set could limit Fewer communities in each set could limit generalizabilitygeneralizability

Could choose communities in different Could choose communities in different countriescountries

RandomizationRandomization

Typically at level of communityTypically at level of community Allows for replication at the level of Allows for replication at the level of

implementationimplementation Realistic model of how the intervention would be Realistic model of how the intervention would be

delivereddelivered RCT does require communities to be willing to be RCT does require communities to be willing to be

randomizedrandomized Multiple baseline could randomize within sets of Multiple baseline could randomize within sets of

communities to determine order of interventioncommunities to determine order of intervention

BlindingBlinding

““Control” groups are often “Usual Care” – i.e. not Control” groups are often “Usual Care” – i.e. not feasible to change normal practice for the control feasible to change normal practice for the control communitiescommunities

Difficult to “blind” participants, impossible to Difficult to “blind” participants, impossible to “blind” providers“blind” providers

Must recognize the “provider” effectMust recognize the “provider” effect Difficult to maintain control communities for long Difficult to maintain control communities for long

trialstrials Repeated Baseline gives promise of intervention Repeated Baseline gives promise of intervention

soon to control communitiessoon to control communities

Duration of StudyDuration of Study

Early studies of elementary school based Early studies of elementary school based interventions showed differences to the end of interventions showed differences to the end of Grade 8 that faded by the end of grade 12 without Grade 8 that faded by the end of grade 12 without further interventionfurther intervention

Secular trends can make research findings Secular trends can make research findings obsoleteobsolete

Important to study end points after the research Important to study end points after the research team has leftteam has left

Need to marry research, evaluation and practiceNeed to marry research, evaluation and practice

Duration of the StudyDuration of the Study

Multiple Baseline design requires multiple Multiple Baseline design requires multiple interventions in multiple communities interventions in multiple communities followed by a comprehensive intervention followed by a comprehensive intervention in several communities to verify the results.in several communities to verify the results.

Some interventions may be of shorter Some interventions may be of shorter duration depending on target (e.g. retailer duration depending on target (e.g. retailer program vs school-based curriculum).program vs school-based curriculum).

Duration of StudyDuration of Study

RCT requires comprehensive interventions RCT requires comprehensive interventions in study communitiesin study communities

For the same total time, the comprehensive For the same total time, the comprehensive intervention could be conducted for a intervention could be conducted for a longer time with the RCTlonger time with the RCT

Both designs require sufficient lead time to Both designs require sufficient lead time to bring the communities “on board”bring the communities “on board”

Both designs require follow-up to assess Both designs require follow-up to assess sustainabilitysustainability

Longitudinal vs Cross-Sectional Longitudinal vs Cross-Sectional DataData

Both designs allow for either longitudinal Both designs allow for either longitudinal data or repeated cross-sectional data on data or repeated cross-sectional data on either individuals or process variableseither individuals or process variables

Repeated cross-sectional data could be Repeated cross-sectional data could be available on adolescent smoking rates from available on adolescent smoking rates from existing surveys, but generally insufficient existing surveys, but generally insufficient sample sizes would be obtained for smaller sample sizes would be obtained for smaller communitiescommunities