The Epidemiological Approach

Question 1

What is epidemiology

Answer 1

• This is about finding causes of disease and preventing disease

Question 2

How do you find out what is different about the people with disease

Answer 2

Find other people with the same disease to see what makes them different.
For example 
-	Sex 
-	Age 
-	Work 
-	Diet 
-	Habits
-	Ethnic groups
-	Genetics – family history

Question 3

What are the ways in which you can investigate whether smoking caused lung cancer

Answer 3

Study design; Prospective cohort study

• Identify 4000 people
• Follow-up for 10 years to see if the smokers had a higher incidence of lung cancer

Alternative study design; Retrospective case control study

• Work backwards
• Ask people with and without lung cancer questions about their smoking habits

Question 4

What in the air can effect lungs

Answer 4

• air pollution

- smoking

Question 5

What is a Prospective Cohort study

Answer 5

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 6

What are the problems with a cohort study

Answer 6

Expensive and lengthy

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

Question 7

What is a Retrospective case control study

Answer 7

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 8

What is the same as saying People without lung cancer are 15 times more likely to a non-smoker that people with lung cancer

Answer 8

People without lung cancer are 15 times more likely to a non-smoker that people with lung cancer same as saying people with lung cancer are 15 times more likely to a cigarette smoker than people without lung cancer

Question 9

Why is there a 15 times increase in males but only a 1 and a half increase in females risk of getting lung cancer

Answer 9

• Women didn’t smoke as much as men

Question 10

How can you show whether saturated fat intake is a cause of ischemic heart disease

Answer 10

if you want to determine whether saturated fat intake was a cause of ischemic heart disease but you are unlikely to find an association as most people have similar diets and have too much fat in your diet

• therefore you need to have an intermediate study for example serum cholesterol levels
• therefore you do a study that shows a relationship between saturated fat intake and serum cholesterol levels
• and then do a study that shows a relationship between cholesterol and ischemia heart disease
• and these two studies together show the relationship between saturated fat intake and heart disease

Question 11

Most diseases are a mixture of

Answer 11

nature and nurture

Question 12

what is PKU

Answer 12

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

Question 13

Describe the pathophysiology of PKU

Answer 13

• 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 14

Is PKU a genetic or environmental disease

Answer 14

• 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 15

The cause of a disease does not have to ..

Answer 15

add up to 100%

Question 16

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 16

= 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 17

Describe the concept of a cause

Answer 17

It need not be something that always results in a particular outcome
And it need not account for all such outcomes

• for example not all smokers get lung cancer
• not all lung cancer is caused by smoking

Question 18

What is the definition of a cause of a disease

Answer 18

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.