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Aetiology and prediction: the difference between pathogenesis and prevention

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Aetiology and prediction: the difference between pathogenesis and prevention

  1. 1. The integration of social and biological mechanisms for healthcare prediction and intervention A follow up from: The integration of social, behavioural and biological mechanisms in models of pathogenesis Mike Kelly, Rachel Kelly, and Federica Russo
  2. 2. Aetiology and prediction: the difference between pathogenesis and prevention Mike Kelly & Federica Russo
  3. 3. Overview The pathogenic approach for communicable diseases Causal models of disease and Predictive models of interventions Non-communicable diseases Why the pathogenic model does not work The contribution of ‘the social’ The role of human behaviour in disease aetiology Predictive models of intervention Regress analysis and the means-end relation 3
  4. 4. THE PATHOGENIC MODEL FOR COMMUNICABLE DISEASES 4
  5. 5. Causes and mechanisms The conceptualisation of disease The outcome of exposure to a pathogen or other noxious factor Pathogens Cause disease Initiate complex mechanisms that lead to disease Complications Multiple pathogens at work Factors that mediate interactions Individuals experience multiple morbidities etc 5
  6. 6. Intervening on the pathogens T1: enough knowledge about good health state, biopathogenesis of disease, risk of getting disease, etc Action A: treatment of disease, alleviation, protection from risk protecting people from microorganisms through isolation, providing clean water, removing sewage, immunisation and improving nutritional status and housing conditions T2: predict evolution of disease, prevention, etc. Underlying conception: Necessary and sufficient conditions 6 T1  A  T2
  7. 7. NON-COMMUNICABLE DISEASES 7
  8. 8. Why the pathogenic model does not work NCDs: non-infectious, non-transmittable among people T1  A  T2 often fails Actions: reduce exposure to some environmental factors; advice about physical activity, nutrition, smoking habits, … How much control do we have? On environmental factors – to some extent On human behaviour – much less 8
  9. 9. Asymmetry between aetiology and prediction in NCDs Aetiology Biopathogenesis of CDs Biological causes and mechanisms Behaviour does contribute to risk in NCDs Aetiology: bio-psycho-social pathogenesis Prediction Public health interventions T1AT2 model has been largely successful Intervention models did not shift to a bio-psycho-social approach Or, if if it did, it happened very late 9
  10. 10. THE CONTRIBUTION OF ‘THE SOCIAL’ TO AETIOLOGY 10
  11. 11. Sociology. And health. Sociology attempts to explain and predict human behaviour Societies manifest observable patterns of change Humans are thinking acting beings Their thought and action take place within the constraints imposed by social structures What links behaviour and health? 11
  12. 12. Social causes are proximal The proximal – distal distinction Biological causes are proximal, social causes are distal Distal causes do not exert direct influence on health Hence, social causes are at best ‘classificatory devices’, but not active causes in disease aetiology Against the proximal – distal distinction 12
  13. 13. The ‘lifeworld’ Relationships with significant others, neighbours, friends Local services, shops Communities and workplaces The immediate physical and microbiological environments Mediates exposure to toxins, hazards, pathogens, etc Drives health states of individuals and populations Is the product of the interaction between human agency and social structure 13
  14. 14. An integrated pathogenic approach The ‘social’ and the ‘biological’ are integrated in the aetiology Behavioural factors are active parts of disease mechanisms An integrated pathogenic approach leads us to rethink models of intervention 14
  15. 15. PREDICTIVE MODELS OF INTERVENTION 15
  16. 16. Communicable diseases Causal model of disease Predictive Model of intervention Recovery / improved health status Biological mechanisms Treatment / public health intervention Exposure to pathogens Biological mechanisms Disease Cause-effect Means-end 16
  17. 17. Non-Communicable diseases Causal model of disease Predictive model of intervention Recovery / improved health status Biological mechanisms Public health intervention Life world Bio-psycho- social mechanisms Disease Multiple bio- psycho- social paths 17 Multipl e means- end relation s
  18. 18. Some remarks The ‘bio-psycho-social paths’ and ‘means-end relations’ complex networks not linear causal relations Models of interventions are conceptualised in terms of means-end: Identify the function of a psycho-social factor Intervening on the function may lead to intervene on something different than the corresponding cause The function of psycho-social factor is highly context dependent 18
  19. 19. What is function? In the context of a causal mechanism: Functions are role-functions The theoretical underpinnings of causal factors They are part of the description of the functioning of a component part of a mechanism A strong conceptual link between functions and causes 19
  20. 20. Example: alcohol consumption, the lifeworld, and interventions
  21. 21. In the pathogenic approach Alcohol consumption is a ‘single’, ‘homogeneous’ behaviour Reduce exposure to the pathogen ( = ethanol) To reduce liver diseases, cancer, obesity, accidents, injury, violence Actions: change in prices, licensing regimes, education campaign 21 T1  A  T2
  22. 22. Alcohol consumption is a social structure It varies across friends, family, social groups, populations, age groups, etc Alcohol consumption is part of the lifeworld of individual and of groups Targeted groups Function of alcohol consumption in their lifeworld Targeted interventions 22 In an integrated pathogenic approach
  23. 23. TO SUM UP 23
  24. 24. For communicable diseases The pathogenic approach is largely successful Causal model of disease Predictive model of intervention For non-communicable diseases The pathogenic approach is wanting on both sides Causal model of disease Integrate bio-social mechanisms Predictive model of intervention Recast causal paths in terms of means-end relation, according to the functions of social factors in the lifeworld 24

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