Post on 31-Mar-2015
transcript
The Intervention Mix
Sevgi O. Aral
Rome, Italy
May 2010
Ipsum lorem . . . !@#$%***??
Single causes for disease states challenged by
→ factors at multiple levels (biological, behavioral, group)
health and disease
→ interrelation among factors includes dynamic feedback + change
Solution: paragidm shift
Public health ≡ complex system
→ complex systems dynamic analytic approaches
Alassio, West Ligurian Riviera, Italy
Condom Use Number of Partners
Sex Work
Casual PartnersMultiple Partners
Early Age at Sexual Debut
Concurrent PartnersShort Gaps
Same Sex Partners
Condom Use
Transactional Sex
Drug Use
Casual PartnersMultiple Partners
Age at Sexual Debut
Concurrent Partners
Forced Sex
Condom Use
Transactional Sex
Drug Use
Casual PartnersMultiple Partners
Age at Sexual Debut
Concurrent Partners
Forced Sex
Clustered risk
behaviorsSyndemics
System of
behaviors
Net effect of
behavior
system
Infection
risk
X
Sexual behaviors
Prevention behaviors
Risk compensationDisinhibition
Relationship among behaviors
Conditional: condoms only with SWS
Contextual: serosorting following accurate and honest disclosure
Relationship among behaviors
Causal:
Circumcision →↑ # of partners
Concurrent partnerships →↑ condom use
Behavioral effects on incidence
Synergistic
Antagonistic
Additive
Duplicative
conditional
eg: risk of UAI with infected
partner >risk of
AI + risk of
sex with
infected
partner
Complex system of behaviors
Complex adaptive system of behaviors
Complex adaptive system?
Complex system?
Complex System
• Interconnected parts
• Non-linear interactions
• Emergent properties
Complex adaptive systems
• Diverse
• Multiple interconnected elements
• Capacity to change
• Capacity to learn from experience
Examples
• Stock market
• Cell & developing embryo
• The brain
• The immune system
Behaviors of an individual =
complex adaptive system
Living organisms – complex adaptive systems
• Multiple participating agents• Hierarchical organization• Extensive organization• Extensive interactions among genetic and
environmental effects• Non-linear responses to perturbation• Temporal dynamics of structure and function• Distributed control• Redundancy• Compensatory mechanisms• Emergent properties
Rea et al., 2006
“ . . . moving beyond the individual into the realm of social and policy processes must surely increase complexity of the causal process exponentially.”
Galea, et al., 2010
ComplexityComplex adaptive systems
Complexity science
HealthMedicine
Health care
XX
Newtonian science
Positivism
Scientism
Reductionism
Complexity science
Complexity theory
Complexity thinking
Health
Medicine
Health care delivery
Individual’s health[d (complex, interrelated, multi-
level factors)]
STD/HIV epidemiology and prevention best described as complex adaptive systems
Complex adaptive system of STD/HIV prevention interventions (CASSPI)
“ . . . the emphasis in prevention research is shifting to evaluation of combination prevention packages in which synergies among interventions with modest levels of effect might lead to substantial efficacy overall.”
Counseling and testing
Condom use
PMCT
↓ Concurrency
Mass media interventions
↓ # partners
Abstinence
Microbidcides
PREP
Male circumcision
Test and treat
→ duplicative, conditional, additive← antagonistic or synergistic
Counseling and testing
Condom use
PMCT
↓ Concurrency
Mass media interventions
↓ # partners
Abstinence
Microbidcides
PREP
Male circumcision
Test and treat
“Multiple interventions from multiple professionals are provided concurrently. Interaction of interventions may significantly influence outcomes. The relatively small, nonsignificant effects of a simple intervention may be magnified when used in combination with other interventions. Interventions that seem effective in isolation may be antagonistic when provided together. In addition, effectiveness of combination of interventions is likely to be different for different patients. It is impossible for a randomized clinical trial to test all possible interactions among interventions encountered in routine practice.”
Horn, et al., 2007
Adherenceduring RCTs > Adherence
during program rollout
> Everyday adherence
Adherence to single intervention > Adherence to
multiple interventions
Timing of interventions
→ Within developmental life course (individual)
→ Within the epidemic trajectory (population)
Population level
Ds in one subpopulation
Compensatory Ds in other subpopulations
Ds in sexual and drug use networks
Unintended, unanticipated net effects
↑ # FSW → ↓ # new HIV infections
↑ # internet based FSW → gonorrhea rates
Scott Cunningham – Baylor University
Internet technology → ↓ relative cost of advertisements
↓ relative cost of security
↑ indoor sex work market
↓ relative share of street work
Epidemiological context (sexual partner network-mixing-concurrency-heterogeneity)
Intervention impact
Epidemiological context
Interactions among interventions
Context: economic, political, social environment
+
budget, organizational capacity, culture
Condom promotion: acceptable, effective
↓ # partners – MSM: politically unacceptable, ineffective
Dr. Thomas Farley,New York City Health
Commissioner
Intervention cost
Available resources
Resource allocation
Cost effectiveness
Comparative effectiveness
Coverage
&
Frequency
↓
Impact of interventions
Dodd, et al., 2010
Required levels of coverage and frequency may be different for systems of interventions
Required coverage vs achievable coverage
POP I Trial
• Effects of single chlamydia test over 12 months overestimated
• Most cases of PID over 12 months not prevented by a single chlamydia screen
• Most cases of PID occurred in women who were negative for chlamydia at baseline
Oakeshott, et al., BMJ, 2010
“Policy makers might consider focusing on more frequent testing of those at higher risk, such as women with a new sexual partner or a recent history of chlamydial infection.”
Targeting
“Who should receive prevention interventions?”
For chlamydia control
Annual screening
<25 — USA
<24 — UK
Universal interventions
For
Highly network-dependent infections
“The impact of many interventions can be amplified by targeting those that are most at risk of acquiring and transmitting infections.”
Garnett & Anderson 1995
→ Impact of targeted vaccination and behavioral interventions
║
Impact of population-wide interventions
→ Follow-up interventions targeting higher risk individuals enhance impact of widespread screening programs
Phase of the epidemic
The extent to which targeting enhances intervention impact
→ During earlier epidemic phases targeting high risk groups is particularly effective
Should all interventions target the same subpopulations?
Targeting
Intervention frequency
coverage
Resources
Costs
Cost effectiveness
Resource allocation
Health system capacity
Duration
Intensity
Sequencing of component interventions
Layering of multi-level interventions
Copyright ©2010 American Public Health Association
Frieden, T. R. Am J Public Health 2010;100:590-595
The health impact pyramid
Frieden’s Health Impact Pyramid focuses on:
Health system infrastructure
Societal composition
Societal organization
Societal operation
Copyright ©2010 American Public Health Association
Frieden, T. R. Am J Public Health 2010;100:590-595
The health impact pyramid
Test and treat
Screening and partner notification
A B C (abstinence, be faithful, condom use)
Counseling and testing
Prevention program perspective
Test & treat
Counseling & testing
Screening & partner notification
Target individual perspective
A B C
Serosorting and condom use
A systematic approach
for
“Context appropriate complex adaptive intervention systems”
Thank you!