LECTURE 6 (Problems with studying humans) Flashcards
What is the ultimate goal of epidemiological studies?
To determine the causes of disease
How do you determine the causes of disease?
1) Observing a possible association between an exposure and an illness
2) Developing a hypothesis about a cause-and-effect relationship
3) Testing the hypothesis through a formal epidemiological study
Studies of which diseases are especially prone to error?
Chronic diseases
What is the most rigorous form of intervention study?
The randomised controlled trial
How do you conduct a randomised controlled trial?
1) Researchers choose a normal group of people and divide them randomly into an experimental group and will instruct them to do certain things (e.g eat a strict low-fat diet) for the next 5 years
2) A control group will be told to do the same things
3) Researchers will monitor both groups, watching for signs (e.g of heart disease) and will justify their hypothesis
What are the limitations in the randomised controlled trial?
- It is impossible to control the behaviour of human beings under such circumstances
- People will lose motivation (unless it’s the only chance to live)
- People may not do it for the necessary length of time
- People might become concerned with their health and stop
How do you conduct a Cohort study?
1) Choose a large group of people who are free of heart disease and ask them detailed questions about their diets etc
2) Over the next five years, compare the health of those who already eat a low-fat diet and those who eat an average diet
What are the advantages and disadvantages of a Cohort study?
ADVANTAGES
- does not require people to change their behaviour
DISADVANTAGES
- correlation doesn’t 100% mean cause because other aspects could be the reason (e.g those with low-fat diet could also exercise more, not smoke)
How do you conduct a Case-control study?
1) Researchers choose a group of people who already have the disease
2) A comparable group of people who do not have the disease would serve as the control group
3) Researchers would question both groups on the past 5 years and decide whether the correlation supports the hypothesis
What are the problems of Case-control study?
- Research information may not be reliable
- People may not remember what they did in the past 5 years
- People might be embarrassed to admit things
- Controls may be different in ways researchers may not have anticipated or be hard to account for in comparison
What do conflicting published reports result in?
Making people distrustful of the news and uncertain about how to protect their health
What are the main sources of error?
- There is a random variation and the association is merely due to chance
[can be counteracted by using large numbers to draw valid conclusions] - Long periods may pass between exposure and development of illness -> difficult to draw conclusions
- Cause-and-effect relationship is not obvious
The ________ the relationship between exposure and disease, the larger the group that must be studied to clarify the relationship
Weaker
What are Confounding variables?
Factors associated with the exposure that may independently affect the risk of developing the disease
(e.g smoking)
How can you avoid possible sources of error?
- Well-designed studies
- Large number of participants
