Mauricio L. Barreto Instituto de Saúde Coletiva Federal University of Bahia

1. AHRC symposium:How should the evidence hierarchy be developed?Social, environmental and biological determinants of health: causal claims and evidence in epidemiology and public health Mauricio L. Barreto Instituto de Saúde Coletiva Federal University of Bahia

2. Diseases in general has multiple causes • In modern times, many of these “causes” are human-made health or non-health related actions (determinants or interventions) that could affect positively or negatively the health of individuals and populations.   They include a wide range of possibilities grouped in technologies, processes, policies, laws, regulations and other ways modern societies intervene at the individual or population level.   

3. The primary “knowledge object” of epidemiological research are the causes of health-related events in populations. • Causal claims in epidemiology has implication on the development of preventative technologies, regulations and policies.

7. Individual/Population Health Social and Economic Policies Institutions (including medical care) Neighborhoods and Communities Living Conditions Social Relationships `` Individual Risk Factors `` Lifecourse Genetic/Constitutional Factors Pathophysiologic pathways Environment

10. Experimental and Observational strategies are used in epidemiological research • EXPERIMENTAL Epidemiological study with a clear experimental component; in which the investigator intentionally alters one or more factors and controls the other study conditions in order to analyze the effects of so doing. Usually, randomized controlled trials; • OBSERVATIONAL Epidemiological study that does not involve any intervention (experimental or otherwise) on the part of the investigator; Most analytical epidemiological designs (e.g, case-control and cohort studies) are properly called observational because investigators observe without intervention other than to record, classify, count, and statistically analyze results.

11. Measuring the effect of interventions: • EFFICACY The extent to which a specific intervention, procedure, regimen, or service produces a beneficial result under ideal conditions; the benefit or utility to the individual or the population of the service, treatment regimen, or intervention. Ideally, the determination of efficacy is based on the results of a randomized controlled trial. • EFFECTIVENESS It is a measure of the extent to which a specific intervention, procedure, regimen, or service, when deployed in the field in the usual circumstances, does what it is intended to do for a specified population. A measure of the extent to which a health intervention fulfills its objectives in practice.

12. Health Interventions BIOLOGICAL BEHAVIOURAL ENVIRONMENTAL SOCIAL “COMPLEX” “SIMPLE” INTERVENTIONS

13. HIERARCHY OF EVIDENCEU.S. Preventive Services Task Force

15. Leroy et al 2009. The impact of conditional cash transfer programmes on child nutrition: a review of evidence using a programme theory framework. Journal of Development Effectiveness, 1:103-129

16. The current “hierarchy of evidence” while useful to define the effect of “simple” interventions, do not even attend all the demands posed at regulatory and policy level decisions regarding this group of interventions, and has yet greater limitations when the effect of “complex” interventions are considered

17. Concluding Remarks • In pharmacological (drugs) or biotechnological (vaccines) interventions the mechanisms are biological based and, as part the current process of drug/biothech development, frequently known before the RCT is conducted. RCTs, using pure counterfactual approach, add information on efficacy and risks. • But, for the “complex” or non-pharmacological interventions or even for deliver “simple” interventions (e.g. a immunization programme), the mechanisms involved are not biological based, and need to be known.

18. Concluding Remarks • Although epidemiologists can, in principle, arguing for causal claims without behavioural/ environmental/social mechanisms, in fact, in many situations they need some understanding of the mechanisms. • Understanding the non-biological mechanisms (behavioural/ environmental/social) are necessary to establish the policy relevance of causal claims in population health, even when there is counterfactual evidences (RCTs or Observational).

19. MECHANISM - In epidemiology and other health, life, and social sciences, the way in which a particular health-related event or outcome occurs, often described in terms of the agents and steps involved. Whereas the focus is often on biological mechanisms, environmental, social, and cultural mechanisms are also relevant to epidemiology, public health, medicine, and related disciplines. MECHANISTIC EPIDEMIOLOGY - Epidemiological research that focuses on mechanisms underlying and explaining associations between determinants and health-related events or states. It is not a formal branch or specialty of epidemiology, nor is it an epidemiological method or philosophy. Loosely, the opposite of “black-box epidemiology.” Porta, 2008. Dictionary of Epidemiology

20. Thanks