The Epidemiological Approach

Question 1

What is epidemiology

Answer 1

Epidemiology is the study of the incidence, distribution and determinants of diseases in humans, with a view to identifying what causes a particular disease and by doing so discovering ways of preventing the disease.

Question 2

how do you define epidemiology

Answer 2

• finding the cause of disease and preventing disease

Question 3

How could you investigate the relationship between smoking and lung cancer

Answer 3

• Prospective (cohort) study

- retrospective (case control) study

Question 4

What are the problems with a prospective (cohort) study

Answer 4

• Expensive and lengthy

- Even with these numbers there would not be enough cases to draw firm conclusions

Question 5

What are the problems with a retrospective (case control study)

Answer 5

• recall bias

Question 6

people with lung cancer are…

Answer 6

People with lung cancer are 15 times more likely to be a cigarette smoker than people without lung cancer

Question 7

How can you link diet and ischaemic heart disease

Answer 7

• look at serum cholesterol levels
• increased in saturated fat intake causes an increase in serum cholesterol levels
• increase in serum cholesterol levels causes an increase in ischaemic heart disease
• can do two separate studies to link increased in saturated faty and serum cholesterol levels and anotehr study in serum cholesterol levels and ischaemic heart disease

Question 8

What is a Prospective Cohort study

Answer 8

A research study that follows over time groups of individuals who are alike in many ways but differ by a certain characteristic (for example, female nurses who smoke and those who do not smoke) and compares them for a particular outcome (such as lung cancer).

Question 9

What is a Retrospective case control study

Answer 9

A retrospective case control study is one that uses existing data to compare two groups. For example, people who have developed a disease might be compared with a group of people who have not.

Question 10

Most diseases are a mixture of

Answer 10

nature and nurture

Question 11

what is PKU

Answer 11

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

Question 12

Describe the pathophysiology of PKU

Answer 12

• this is caused by a lack of the enzyme phenylalanine
• this means that without pehnylalanine hydroxylase phenylalanine can get converted to keto acids which are toxic and can cause mental retardation

Question 13

Is PKU a genetic or environmental disease

Answer 13

• Normally it is converted to tyrosine which is converted to melanin, but without phenylalanine hydroxylase phenylalanine gets converted to keto acids which are toxic and can cause mental retardation
• Therefore, from the geneticist view the disease in 100% genetic
• But the disease can be completely prevented by restricting dietary phenylalanine
• • therefore the epidemiologist view is the disease is 1000% environmental

Question 14

The cause of a disease does not have to .

Answer 14

add up to 100%

Question 15

describe how you would work out the percentage of disease that is prevented

example: Preventing heart disease with three drugs
- Anti-platelet drug (aspirin) prevents 30%
- Cholesterol lowering drug (statin) prevents 60%
- Blood pressure lowering drug prevents 20%
in 100 cases of the disease

Answer 15

= there are 100 cases of the disease so 30 cases will be prevented by aspirin

• this leaves 70 of which 42 (60%) would be prevented by the statin
• this leaves 28 of which 6 (20%) would be prevented by the blood pressure lowering drug leaving 22
• so 78% would be prevented (30+42+6)

Question 16

What is the definition of a cause of a disease

Answer 16

The CAUSE OF A DISEASE is a factor that is associated with the incidence of the disease so that if the intensity or prevalence of the factor in a population changes, the incidence of the disease changes in ways that cannot be explained by changes in other factors.