Congressional Budget Office
February 4, 2014

Designing Policy Interventions to Address Obesity:
Research and Analytic Cha...
Defining, Measuring, and Projecting Obesity
Alternative measures of obesity associated with different health
risks/degrees...
Effects of Obesity on Health
Risk factor for:
–
–
–
–
–

Multiple chronic conditions
Adverse pregnancy outcomes
Disability...
Effects of Obesity on Health Care and Disability Costs
Wide variation in estimates of:
– Health care costs attributable to...
Assessing Effects of Interventions
(for Prevention and/or Mitigation)
Different types of interventions  different evaluat...
Evaluating Interventions Targeting Individuals or Defined
Groups: Internal Validity
Does intervention improve health and/o...
Evaluating Interventions Targeting Individuals or Defined
Groups: External Validity
How generalizable are findings to broa...
For Further Information

linda.bilheimer@cbo.gov
202/226-2676

CONGRESSIONAL BUDGET OFFICE
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Designing Policy Interventions to Address Obesity: Research and Analytic Challenges

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Presentation by Linda Bilheimer, CBO’s Assistant Director for Health, Retirement, And Long-Term Analysis, to the 2014 National Health Policy Conference

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Designing Policy Interventions to Address Obesity: Research and Analytic Challenges

  1. 1. Congressional Budget Office February 4, 2014 Designing Policy Interventions to Address Obesity: Research and Analytic Challenges Presentation to the 2014 National Health Policy Conference Linda T. Bilheimer, Ph.D. Assistant Director for Health, Retirement, and Long-Term Analysis
  2. 2. Defining, Measuring, and Projecting Obesity Alternative measures of obesity associated with different health risks/degrees of risk: – Body mass index (BMI) • Easiest to measure and self-report, but subject to reporting error • Sometimes misleading : Elderly people? Racial and ethnic subpopulations? – Body fat percentage – Central adiposity (excess abdominal fat) • More relevant for elderly people? Duration matters recent focus on “obesity years”: – Challenging to measure due to recall bias, few longitudinal studies Issues with projecting future obesity prevalence: – Weighting recent vs. historical trends – Projecting BMI categories vs. shifts in BMI distribution – Incorporating duration CONGRESSIONAL BUDGET OFFICE
  3. 3. Effects of Obesity on Health Risk factor for: – – – – – Multiple chronic conditions Adverse pregnancy outcomes Disability Dementia? Mortality—protective effects for elderly? Challenges of isolating effects: – – – – – – Competing health risks Variation across lifespan Effects of prior obesity years Varying relationships between effects and measures Changing relationships over time Variation among population subgroups CONGRESSIONAL BUDGET OFFICE
  4. 4. Effects of Obesity on Health Care and Disability Costs Wide variation in estimates of: – Health care costs attributable to obesity – Effects on subsequent costs of: • Preventing obesity among populations at risk • Intentional weight loss among obese people Challenges of isolating effects and specifying counterfactuals: – – – – Competing health risks Other individual characteristics with independent effects on costs Non-linearity; concentration of additional costs among severely obese Reverse causality Effects on payers: – Dependence on prevalence of obesity/severe obesity, and varying effects, among population subgroups – Interactions of longevity and disability effects: Implications for Medicare and Medicaid CONGRESSIONAL BUDGET OFFICE
  5. 5. Assessing Effects of Interventions (for Prevention and/or Mitigation) Different types of interventions  different evaluation questions and research issues: – Clinical interventions for individuals: behavioral, pharmaceutical, surgical, combinations – Interventions targeting defined groups: community-, school-, or employment-based – Interventions targeting populations: laws and regulations, excise taxes Issues with evaluation studies: – Methodological weaknesses – Wide ranges of conclusions – Publication biases Challenges for systematic reviews: – Weighting older studies CONGRESSIONAL BUDGET OFFICE
  6. 6. Evaluating Interventions Targeting Individuals or Defined Groups: Internal Validity Does intervention improve health and/or reduce costs of participants? – What is basis for comparison? • Randomized controlled trials vs. observational comparison groups • Addressing observed and unobserved differences with observational comparison groups – How are outcomes measured? • Intermediate measures: weight, biomarkers • Health status measures: chronic conditions, disability, mortality • Health care costs: challenges of small sample sizes and high-cost cases – How is confounding addressed? • Smoking, physical activity, comorbidities, socioeconomic status, etc. – What time frames are considered? • Focus on relatively short-term intermediate outcomes • Inferences for longer-term health status outcomes (given difficulty of maintaining weight loss/healthy behaviors) – How is attrition accounted for? • Intent-to-treat vs. completers • Imputation methods for non-completers CONGRESSIONAL BUDGET OFFICE
  7. 7. Evaluating Interventions Targeting Individuals or Defined Groups: External Validity How generalizable are findings to broader population and to everyday practice? ‒ How is sample selected? • Representativeness of people eligible to participate—of overall population and key subgroups • Differences between participants and nonparticipants (among those eligible) ‒ How should findings from controlled clinical studies be used? • Efficacy vs effectiveness in everyday practice • Converting from clinical to community-based interventions CONGRESSIONAL BUDGET OFFICE
  8. 8. For Further Information linda.bilheimer@cbo.gov 202/226-2676 CONGRESSIONAL BUDGET OFFICE

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