Causes and probabilitiesfor health

Federica Russo

Center Leo Apostel, Free University BrusselsCenter for Reasoning, University of Kent

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Overview

Medical humanities and philosophy of science

Causes for health

Probabilities for health

For whom? For what?

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PHIL SCI PERSPECTIVEON MEDICINE

Medical Humanities

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The ‘human’ study of medicine

Medicine, experimental medicine, and the biological understanding of wellness and disease

Medical humanities bring ‘Man’ into medicineAnthropological, psychological, sociological,

philosophical understanding of wellness and disease

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Phil med moves beyond ethics

Traditional phil med is about ethics

Fresh philosophical look at medicine:How do we know: epistemology and methodology

of medical researchWhat it is: metaphysics of the ‘objects’ of medicine

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TYPICAL QUESTIONS IN PHIL MEDMedical Humanities

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Ethics questions, e.g.:

Is it ethical to conduct research on stem cells?

Should we accept euthanasia?

Is it ethical to deliver web-based diagnoses online to patients?

…

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Phil Sci questions, e.g.:

What notion of cause is applicable to biomedical contexts?

How to interpret probability in biomedical contexts?

What procedures grant extrapolation from animal models to humans?

…

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EXAMPLESMedical Humanities

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Do electromagnetic fields cause brain tumour?

John lived 40 years close to an antenna tower. Did this cause him cancer?

How much is the risk of developing CHD lowered if I quit smoking?

Did the campaign in schools lower smoking rates?

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GENERIC AND SINGLE CASECauses for Health

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Medical knowledge and Personalised medicine

Medical knowledge: Generic causal relations

Are in principle repeatable

Are supposed to hold of the majority of the population

Epidemiological studies plus lab results

Personalised medicine: Single Case causal relations

Are tailored to the individual patient

Make use of specific, unique information about the patient

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LEVELS OF CAUSATIONCauses for Health

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A chicken-egg question?

No primacy of either level

Mutual need of both levels

An iterative process

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GENERIC AND SINGLE CASEProbabilities for Health

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Different levels of causation, different interpretations of probability

GenericHeavy smokers have 10 times more chances

to develop lung cancer

Frequency of occurrence of disease in a given population

Single CaseJohn’s chances of recovery after operation are 80%

Degree of belief in occurrence of a specific event

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CAUSES AS DIFFERENCE-MAKERSCauses for Health

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What causes are, what causes do

A virus causes infection

Penicillin cures infection

Socio-economic status influences access to healthcare

Smoking restricts blood vessels

Different ‘things’ can be causes

What they all do is to make a difference

to a condition of health or of disease

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VARIATIONAL EPISTEMOLOGY AND METHODOLOGY

Causes for Health

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Look at variations in order to …

Find out causes of disease

Find out causes of recovery

Find out regulatory mechanisms

Comparisons between groups

Exposed / unexposed; healthy / ill

What makes conditions vary across groups / individuals

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ODDS AND RISKSProbabilities for Health

Risks, Odds and Probabilities:Easy to compute

Risks and odds compare proportions in groups

Factor Disease

Yes No

Exposed n11

p11

n12

p12

Unexposed n21

p21

n22

p22

exp

exp

/

/

/

/

;

un

n n n pRR

n n n p

Odds n nOR

Odds n n

Odds PP Odds

Odds P

11 11 12 11

21 21 22 21

11 12

21 22

1 1

Risks, Odds, and Probabilities ‘explained’

… a RR equal to 2.0 means that an unexposed person is twice as likely to have and adverse outcome as one who is not exposed …

(Sistrom & Garvan 2004)

… odds and probabilities are different ways of expressing the chance that an outcome may occur…

(Sistrom & Garvan 2004)

… the probability that a child with eczema will also have fever is estimated by the proportion 141/561 (25.1%) …

(Bland & Altman 2000)

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Risks, Odds, and Probabilities explained

‘unexposed person’, ‘child’ are statistical individualsindividuals randomly sampled from the population

Odds and risks compare proportions in groupsThey have a generic interpretation

The corresponding probabilities are generic too

They are not directly applicable to the single-caseTo be applicable they need to be constrained by further single

case knowledge

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FOR WHOM? LAYMEN

What do laymen understand:

Out of doctor’s explanation?

In self, web-based diagnoses?

In 123&me genetic mapping?

In Wiki Medicare?

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FOR WHOM? MEDICAL PRACTITIONERS

How can a better

understanding

of phil med issues

improve medical practitioners’

explanations?

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FIGHT STATISTICAL HEGEMONYFor What?

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Evidence-based people claim they can get ‘medical causes’ out of statisticsNot so sure, though

A point about philosophy of science

What information is conveyed by statisticsA point about communication of science

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RECONCILE WESTERN ANDNON-WESTERN HEALINGS

For What?

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Compare, set up a dialogue

What can Western medicine learn from other ways of healing? And vice-versa.

Salvage expert knowledge in the era of evidence.After ethno-biology, ethno-medicine?

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To sum up

A gentle introduction to phil med for non-philosophers (Hopefully!) Medical humanities, phil sci in medicine

Causes and probabilities for healthFor populations, for individualsMedical knowledge, diagnosis

Whom is this philosophy good for? (Hopefully!)Laymen, medical practitioners