The%20Guide%20to%20Community%20Preventive%20Services

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Laurie Anderson, PhD, MPH Centers for Disease
Control Prevention February 10, 2004
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Outline I. Difference between a literature review
and a systematic review II. Purpose of the Guide
to Community Preventive Services systematic
reviews evidence-based recommendations III.
Steps in carrying out a systematic reviews IV. An
example
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The difference between a literature review and
a systematic review
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When making decisions about the choice of an
intervention
The body of intervention literature can be quite
large, inconsistent, and uneven in quality.
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Literature Reviews
A literature review has typically been used to
provide background information for intervention
selection. These reviews present a group of
studies, with strengths and weaknesses discussed
selectively and informally.
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• Traditional literature reviews have several
  shortcomings
• The process is subjective. There are few formal
  rules, two reviewers might reach different
  conclusions.
• Lack explicit criteria for excluding
  inappropriate or poorly done studies.

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Typically a literature review counts the number
of studies supporting, or not supporting, an
intervention i.e. positive, negative, or no
effect but ignores sample size, effect size and
research design. This can lead to erroneous
conclusions about intervention effectiveness.
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In literature reviews conflicting findings may
lead to a conclusion that an intervention is
ineffective or the research is uninterpretable.
Systematic reviews exploit divergent findings by
examining potential explanations --- treatment
differences, setting differences, etc. ---
because conflicting outcomes may tell us where
an intervention is likely to succeed or fail.
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• Systematic reviews use numeric and narrative
  information fully
• a small effect across several studies may be
  significant
• program characteristics can be used to explain
  the effect.

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• Literature reviews are an inefficient way to
  extract program outcome information,
  particularly if the number of studies is large,
  e.g.gt30.
• It is impossible to mentally juggle relationships
  among so many variables.

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Systematic Reviews

• Another approach to the literature is systematic
  reviews.
• A systematic review takes in account
• the precise purpose of the review
• i.e. stating a research hypothesis
• how studies are selected included

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• Systematic reviews can answer
• is there publication bias?
• are intervention programs similar enough to
  combine?
• what is the distribution of study outcomes?

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• Systematic review can answer
• are outcomes related to research design?
• are outcomes related to characteristics of
  programs, participants, and setting?
• what are the needs for future research?

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Purpose of the Guide to Community Preventive
Services systematic reviews evidence-based
recommendations
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Are we building on a foundation of existing
knowledge?

• Explosive growth of scientific information
• too much to keep up with
• contradictory results
• Increasing public doubt about scientific findings

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Systematic reviews for research synthesis

• combine many studies with different methods and
  results
• look for consistencies in set of findings
• more robust than single study
• may pinpoint why studies differ
• shows what is effective and why

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What counts as evidence?

Type 1 Type 2
Determinants or associations between risk and an outcome Relative effectiveness of different interventions
Something should be done This should be done
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The Guide to Community Preventive Services

• What strategies, targeted to which groups will
• promote healthy choices?
• prevent disease and injury?
• improve environmental conditions to promote
  health?

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Community Guide Topics
Environmental Influences Environmental Influences
Sociocultural Environment Physical Environment Sociocultural Environment Physical Environment
Risk Behaviors Specific Conditions
Tobacco Use Alcohol Abuse/Misuse Other Substance Abuse Poor Nutrition Inadequate Physical Activity Unhealthy Sexual Behaviors Vaccine Preventable Disease Pregnancy Outcomes Violence Motor Vehicle Injuries Depression Cancer Diabetes Oral Health
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Central Questions

• program effectiveness
• feasibility of implementation
• acceptability to the population
• unanticipated harms (or benefits)
• cost-effectiveness

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Steps to Conducting a Review

• Assemble a review team
• Develop conceptual framework
• Prioritize review topics
• Define specific intervention for review
• Search for and retrieve evidence
• Rate quality of evidence
• Summarize evidence
• Translate into a recommendation

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Assemble a Review Team

• Multiple perspectives and backgrounds
• Improve completeness and accuracy of information
• Reduce impact of individual/institutional
  perspectives
• Enhance usefulness of products

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Develop Conceptual Approachto the Topic

• The Logic Model

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LOGIC FRAMEWORK ILLUSTRATING CONCEPTUAL APPROACH
TO NUTRITION COMMUNITY HEALTH
Interventions
Modifiable Determinants
Intermediate Outcomes
Community Health Outcomes
POPULATION FOOD INTAKE Food
Consumption Patterns (e.g.
fruits, vegetables) Intake of Nutrients and Food
Components Vitamins Minerals Fiber Fats Other
food constituents Dietary supplements Alcohol Ener
gy balance
Food Supply Factors -Agriculture
policy -Nutrition policy -Science and technology
-Food production, processing, storage and
distribution -Food fortification -Food safety
Physiologic Indicators Growth Adipose
tissue Musculoskeletal Gastrointestinal Metabolic
Cardiovascular Reproductive Immunological Neurolog
ical
Morbidity Mortality Measures of Health
Fitness
Environmental Factors
Availability Price -Neighborhoods -Schools -Work
sites -Homes -State and National -Food and
nutrition assistance programs
Life Stage Requirements Pregnancy Lactation
Childhood Adolescence Adulthood
Older Adulthood
Genetics, Co-morbidities
Consumer Demand -Household
resources -Nutrition knowledge -Cultural
practices -Psychosocial characteristics -Taste
and preferences -Advertising and marketing
Physical Activity Patterns
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Prioritize Intervention Topics

• Preventable disease burden
• Common practices that are questionable
• New approaches that are promising
• Topic of keen public health interest

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• Priority Ranked List of Topics 
• Food beverage availability and price in
  schools.
• Comprehensive community approaches to increase
  fruity vegetable intake.
• Food and beverage advertising to children.
• Food beverage availability, price, portion
  size, and labeling in restaurants.
• Tax on sodas and snack foods.
• Farm subsidies and production of fruits,
  vegetables, whole grains.

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7. Food choice and nutrition education in food
assistance programs. 8. Nutrition and weight
management counseling in healthcare
settings. 9. Breast-feeding. 10 Product labeling
in grocery stores, restaurants and vending
machines. 11. Food beverage availability and
price in worksites. 12. Use of dietary
supplements across the lifespan.
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Specify the Review Question

• What population?
• What interventions or risk factors?
• What comparisons?
• What outcomes?

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Example Question

• Do multi-component, school-based nutrition
  interventions which may include
• curricula (nutrition physical activity)
• food availability, accessibility, price
• policy and environmental changes
• improve nutritional behavior and nutritional
  status of children and adolescents in developed
  countries?

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Analytic Framework
Behaviors dietary intake physical activity
School Policy
Environmental support for healthy choices
Knowledge nutritional needs food
content Attitudes self-care body
image Abilities self-assessment behavioral
change skills media literacy

Physiologic Indicators body size
composition growth fitness Health status blood
pressure cholesterol School Achievement attendance
participation performance
Multi-component School-based Nutrition Interventio
ns
Nutrition health messages
Promotion of self-awareness, self-efficacy
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Inclusion Criteria

• Characteristics derived from the focused question
  
• Additional characteristics
• Methodological
• Publication dates
• Languages
• Relevant outcomes

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Find Information

• Select strategies for finding studies
• Database searches
• Reviews of reference lists
• Gray literature
• Consultation with experts

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Assess Quality

• Suitability of study design
• see handout
• Quality of study execution
• see handout

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Suitability of Study Design

• Greatest
• Prospective and
• Concurrent comparison
• Moderate
• Retrospective or
• Multiple measurements over time no concurrent
  comparison
• Least
• Single before and after measurement no
  concurrent comparison

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Strength of Study Execution

• Description
• Population
• Intervention
• Sampling
• Measurement
• Exposure
• Outcome
• Analysis
• Interpretation of results
• Other

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Exclude Studies Below Some Quality Threshold

• Exclude studies with limited execution (i.e.,
  with many important threats to validity)
• Sometimes exclude studies with least or moderate
  suitability of design

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Research Synthesis for Public Health Policy
Practice DecisionsSystematic review of United
States studies of .08 blood alcohol concentration
laws
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Lowering legal blood alcoholconcentration (BAC)
limits

• Alcohol-related crashes cause 16,000 deaths and
  300,000 injuries each year in the US
• Laws that lower BAC from 0.10 to 0.08 existed in
  less that half of US states

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Analytic FrameworkLower Blood Alcohol
Concentration Laws
Perceived Risk of Arrest
Lower B.A.C. Laws
OUTCOME
Alcohol- related crashes
Drinking driving behaviors
Fatal non-fatal injuries
Social norms regarding drinking and driving
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Evidence base for .06 BAC Laws
Searched journal articles, technical reports and
conference proceedings. Nine studies were
identified evaluated state BAC laws all of
sufficient design and quality. All studies
reported data from police incident reports of
crashes on public roadways.
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Evidence base for .06 BAC Laws
Eight of the nine studies reported percent change
in alcohol-related fatalities (post-law period
vs. pre-law period. Other outcome data included
public knowledge and perception of impaired
driving laws, self-report of impaired driving,
impaired driving arrests.
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Percent Change in Measures of Alcohol
-
Related Motor
Vehicle Fatalities, by State


States



15 States (1)

Median percent change
-
7


Interquartile range
-
15,
-
4

VA (2)


VT (3,4,5)


UT (5,3,4)


OR (4,5,3)


NC (6,2)


NM(2)


NH (2)


ME(4,5,3)


KS (2)


FL (2)


CA (5,7,8,3,4)



50
-40
-30
-20
-10 0 10
20 30

Percent Change


Median percent change -7




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States with .08 BAC Laws, 2002
Passed .08 BAC law before the new national
standard
Passed .08 BAC law in 2001
Passed .08 BAC law in 2002
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Who Is the Audience?

• Public health departments
• Health care systems
• Purchasers of health care
• Government and foundations
• Community organizations

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Lack of Persuasive Evidence

• Lack of evidence does not mean that interventions
  dont work
• Insufficient evidence may point to a research
  agenda

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Issues of Evidence

• We dont have evidence about everything

• Enormous amount of evidence yet to review

• New evidence may change recommendations

• Capturing complexity

• Urgent needs and limited resources

• Participatory research

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