Download Complex adaptive systems

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
Multiple Partners
Casual Partners
Concurrent Partners
Condom Use
Age at Sexual Debut
Transactional Sex
Drug Use
Forced Sex
Clustered risk
behaviors
Syndemics
System of
behaviors
Net effect of
behavior
system
Infection
risk
X
Sexual
behaviors
Prevention
behaviors
Risk compensation
Disinhibition
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
Complexity
Complex adaptive systems
Complexity science
Health
Medicine
Health care
Newtonian
science
Complexity
science
Positivism
Complexity
theory
XX
Scientism
Reductionism
Complexity
thinking
Health
Medicine
Health care delivery
Individual’s health
[d (complex, interrelated, multilevel 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.”
↓ Concurrency
↓ # partners
Test and treat
Counseling and testing
Mass media interventions
PMCT
Microbidcides
Condom use
Abstinence
→ duplicative, conditional, additive
← antagonistic or synergistic
PREP
Male circumcision
↓ Concurrency
↓ # partners
Test and treat
Counseling and testing
Mass media interventions
PMCT
Abstinence
Microbidcides
Condom use
PREP
Male circumcision
“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
Adherence
during RCTs
>
Adherence
during
program
rollout
Adherence to single
intervention
>
>
Everyday
adherence
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 networkmixing-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?
Resources
Targeting
Intervention
frequency
coverage
Costs
Cost effectiveness
Resource
allocation
Health system
capacity
Duration
Intensity
Sequencing of component interventions
Layering of multi-level interventions
The health impact pyramid
Frieden, T. R. Am J Public Health 2010;100:590-595
Copyright ©2010 American Public Health Association
Frieden’s Health Impact Pyramid focuses on:
Health system infrastructure
Societal composition
Societal organization
Societal operation
The health impact pyramid
Frieden, T. R. Am J Public Health 2010;100:590-595
Copyright ©2010 American Public Health Association
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
ABC
Serosorting and condom use
A systematic approach
for
“Context appropriate complex adaptive
intervention systems”
Thank you!