PHEPB: Quantifying benefits of disease prevention

Question 1

How can we prevent diseases?

Answer 1

By removing a cause of a disease- stop/do not start cigarette smoking to reduce risks of CHD, lung cancer, other conditions

Strengthening resistance of host- immunisation, imporved nutrition to reduce risk of infection

Interfereing with disease pathogenesis- antiplatelet medications in CHD, reduced risk of CHD events and strokes

Question 2

How are preventions classified?

Answer 2

Question 3

What is primary prevention?

Answer 3

Question 4

Describe secondary prevention

Answer 4

Question 5

What is tertiary prevention?

Answer 5

Question 6

Is there a scope of overlap in prevention types?

Answer 6

Question 7

Describe 4 measures when describing the importance of a disease cause in the population

Answer 7

RELATIVE RISK → strength of causality

ATTRIBUTABLE RISK → impact of cause on indvidual group

POPULATION ATTRIBUTABLE RISK → overall amount of disease risk in the population, associated with a particular cause

POPULATION ATTRIBUTABLE RISK FRACTION → proportion of all disease in the population associated with that cause

Note that for all these measures you need to define a control group which is NOT exposed to the cause

Question 8

How do we obtain info about these measures to describe disease importance?

Answer 8

Question 9

What is relative and attributable risk?

Answer 9

Relative risk= risk in exposed (high) group DIVIDED BY risk in unexposed (normal) group
-Measures how powerful a causal factor (eg high bp) is for disease
-Helpful bc it often consistent across a whole population

Attributable (excess) risk= Risk in exposed (high) group MINUS the risk in unexposed (normal) group
-Measures the effect of the factor on risk in individuals
(and groups of individuals)

Question 10

Use this data to calculate relative and attributable risk

Answer 10

Question 11

What is population attributable risk?

Answer 11

Population attributable risk
Population attributable risk fraction
These take account not only the amount of risk, but also the proportion of the population affected by it

And again, below we’ve got our low risk, normal blood pressure population and our high blood pressure population.
But now we’re also taking account that ~20% of the population have normal BP, 80% of the population actually have high BP.

Question 12

How do we calculate population attributable risk (PAR)?

Answer 12

Question 13

Use this data to calculate PAR

Answer 13

Question 14

What is population attributable risk FRACTION? How do you calculate it ?

Answer 14

Question 15

Use this data to calculate pop attributable risk FRACTION

Answer 15

Question 16

What should you be aware of when doing calculations such as PAR and PARF?

Answer 16

Question 17

We may prevent the harm associated w high BP using either a HIGH or POPULATION risk strategy approach. Describe the high risk approach

Answer 17

Question 18

We may prevent the harm associated w high BP using either a HIGH or POPULATION risk strategy approach. Describe the population risk approach

Answer 18

eg, you can lower BP in the wole population using weight loss, less alc + salt intake initiatives etc

Question 19

What are the strengths of high risk strategy?

Answer 19

Rather similar to clinical practice, so can offer intervention appropriate to individual
* Because subject at high risk, intervention can be effective + cost effective
* Motivation of subject and doctor tends to be high
* Approach fits within medical model
* Avoids interference with low-risk population

Question 20

What are the weaknesses of high risk strategy?

Answer 20

Process involves risk factor screening= imperfect prediction of risk and is costly
Limited efforts to interfere w disease incidence, so this is a palliative strategy for prevention, not a radical one
Represents medicalization of health and prevention
Often behaviourally inappropriate – singling out a small subset of the pop who must behave differently from others

Question 21

What are the strengths of population risk strategy?

Answer 21

Radical, aiming to reduce disease incidence
Large potential benefits esp where risk is widespread in population
Behaviourally appropriate - no singling out
Does not require screening/identification of a high risk group
Does not depend on spenny medical care services

Question 22

What are the weaknesses of population risk strategy?

Answer 22

Depends on a sense of public purpose- individuals + HCWs are poorly motivated
Measures needed may be complex
Though population benefit can be large, individual benefit
(even high risk individuals) is small
If the population strategy involves adding a new factor w potential adverse effects (e.g. fluoride into drinking water) the balance of benefit vs harm may be v narrow

Question 23

Which primary prevention strategy is more effective?

Answer 23

Question 24

How does this data show a Rose Paradox?

Answer 24

Question 25

Describe what is going on in this table

Answer 25

Question 26

So what is the best choice of prevention strategy?

Answer 26

Question 27

What could favour a high risk strategy?

Answer 27

Question 28

What is the limitation about focusing on a single risk factor?

Answer 28

Have focused here on high blood pressure and CHD
But high blood pressure is only one of several causal factors for coronary heart disease, eg smoking and high LDL-cholesterol
These factors have multiplicative effects on CHD risk
Therefore it is much more effective to use a risk score inc SEVERAL risk factors, and reduce all of these