The Epidemiological Approach

Question 1

What is epidemiology briefly?

Answer 1

Finding causes of disease and preventing disease

Question 2

Percival Potts noticed that a high proportion of his patients with scrotal cancer were/had been chimney sweeps. These results were limited to Britain. Why?

Answer 2

The difference was that British chimney sweeps did not

bathe regularly compared to chimney sweeps in Germany for example.

Question 3

Why is lung cancer more common in men?

Answer 3

More exposure to pollution e.g. due to occupation

Smoke more

Question 4

What type of study is used to investigate the relationship between smoking and lung cancer?

Answer 4

Prospective cohort study

Question 5

What are the problems with a cohort study? (3)

Answer 5

Expensive
Lengthy
Need very large numbers to draw firm conclusions

Question 6

What type of study is quicker than a cohort study?

Answer 6

Case control study

Question 7

How can the relationship between saturated fat intake and ischaemic heart disease be assessed?

Answer 7

A study to assess the link between saturated fat intake and serum cholesterol, and a study to assess the link between serum cholesterol and IHD. Together they show the relationship between fat intake and IHD.

Question 8

What is PKU?

Answer 8

Phenylketonuria, an inborn error of metabolism in which there is a congenital lack of the enzyme phenylalanine hydroxylase.

Question 9

What does phenylalanine hydroxylase do?

Answer 9

Converts phenylalanine to tyrosine

Question 10

How can PKU be prevented?

Answer 10

Restricting dietary phenylalanine

Question 11

If…
Anti-platelet drug (aspirin) prevents 30% of cases of heart disease
Cholesterol lowering drug (statin) prevents 60%
Blood pressure lowering drug prevents 20%
How many cases can be prevented by all three drugs together?

Answer 11

78%

Working out:
100 cases of the disease.
30 would be prevented by aspirin.
This leaves 70, of which 60% would be
prevented by the statin = 42 cases.
This leaves 28, of which 20% would be
prevented by the blood pressure lowering drug = 6.
30 + 42 + 6 = 78
Therefore 78% of cases prevented.

Question 12

What is the definition of a cause of a disease?

Answer 12

A factor that is associated with the disease so that if the

intensity or frequency of the factor in a population is changed, the frequency of the disease also changes.