Aetiology and prediction: the difference between pathogenesis and prevention

The integration of social and biological mechanisms

for healthcare prediction and intervention

A follow up from:

The integration of social, behavioural and biological mechanismsin models of pathogenesis

Mike Kelly, Rachel Kelly, and Federica Russo

Aetiology and prediction:the difference between

pathogenesis and prevention

Mike Kelly & Federica Russo

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Overview

The pathogenic approach for communicable diseasesCausal models of disease and Predictive models of interventions

Non-communicable diseasesWhy the pathogenic model does not work

The contribution of ‘the social’The role of human behaviour in disease aetiology

Predictive models of interventionRegress analysis and the means-end relation

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THE PATHOGENIC MODEL FOR COMMUNICABLE DISEASES

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Causes and mechanisms

The conceptualisation of diseaseThe outcome of exposure to a pathogen or other noxious factor

PathogensCause diseaseInitiate complex mechanisms that lead to disease

ComplicationsMultiple pathogens at workFactors that mediate interactionsIndividuals experience multiple morbiditiesetc

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Intervening on the pathogensT1: 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

T1 A T2

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NON-COMMUNICABLE DISEASES

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Why the pathogenic model does not work

NCDs: non-infectious, non-transmittable among people

T1 A T2 often failsActions: reduce exposure to some environmental factors; advice about physical activity, nutrition, smoking habits, …

How much control do we have?On environmental factors – to some extentOn human behaviour – much less

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Asymmetry between aetiology and prediction in NCDs

AetiologyBiopathogenesis of CDs

Biological causes and mechanisms

Behaviour does contribute to risk in NCDs

Aetiology: bio-psycho-social pathogenesis

PredictionPublic health interventions

T1AT2 model has been largely successful

Intervention models did not shift to a bio-psycho-social approachOr, if if it did, it happened very

late

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THE CONTRIBUTION OF ‘THE SOCIAL’ TO AETIOLOGY

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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?

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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

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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

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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

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PREDICTIVE MODELS OF INTERVENTION

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Communicable diseases

Causal model of disease Predictive Model of intervention

Cause-effectM

eans

-end

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Non-Communicable diseases

Causal model of disease Predictive model of intervention

Multiple bio-

psycho-social paths

Multiple

means-end

relations

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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 factorIntervening on the function may lead to intervene on something

different than the corresponding causeThe function of psycho-social factor is highly context dependent

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What is function?

In the context of a causal mechanism:Functions are role-functions

The theoretical underpinnings of causal factorsThey are part of the description of the functioning of a component part of a mechanism

A strong conceptual link between functions and causes

Example:alcohol consumption,

the lifeworld, and interventions

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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

T1 A T2

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Alcohol consumption is a social structure

It varies across friends, family, social groups, populations, age groups, etcAlcohol consumption is part of the lifeworld of individual and of groups

Targeted groups

Function of alcohol consumption in their lifeworld

Targeted interventions

In an integrated pathogenic approach

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TO SUM UP

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For communicable diseasesThe pathogenic approach is largely

successfulCausal model of diseasePredictive model of intervention

For non-communicable diseasesThe pathogenic approach is

wanting on both sidesCausal model of disease

Integrate bio-social mechanisms

Predictive model of interventionRecast causal paths in terms of

means-end relation, according to the functions of social factors in the lifeworld