Attribute risk and strategies for prevention. Flashcards
If a risk ratio of disease A and odds ratio of disease B are equal in value then the association seen in both diseases are the same. True or false?
False. A risk ratio shows stronger association as the odds ratio is always further from the null.
Why do you need to take into account relative ratios instead of just using association measures?
As relative measures are needed to take into account impact at the population level.
What are absolute measures used for (2 things) ?
- Policy decisions.
2. To allocate resources.
Name three examples of absolute measures.
- Risk difference.
- CI.
- Prevalence.
What are relative measures used for?
- To determine the strength of association.
- To determine a causal relationship.
- To explore aetiology.
What does attributable risk assume (3 things)?
- Causal relationship.
- No source of bias.
- The distribution of other known and unknown factors is the same in exposed and unexposed groups (this includes background exposure).
What does the attributable risk assess?
The impact of removing the exposure from the whole population or from exposed individuals.
Background exposure is a constant. True or false?
It is true in a given population but varies between populations.
What should you always state when stating the AR?
A time period.
What is the formula for the AR?
AR= R1-R0.
When will you use the term ‘risk difference’ instead of ‘attributable risk’?
When you do not know if the exposure is a causal factor.
What does NNT stand for?
Number needed to treat.
What formula for NNT is needed to prevent one case of disease?
1/AR.
What is the definition of AR%?
The proportion of disease in the exposed group that can be attributed to the exposure of interest. This proportion of disease could be removed if you removed the exposure.
What is the formula of the AR%?
(Iexposed-I unexposed)/1exposed = (RR-1)/RR x100.
You should always define AR correctly so you know if you are referring to the exposed or unexposed group. True or false?
False. AR always refers to the exposed group.
If an exposure is protective you use a negative RD value. True or false?
False. You can but it is better to switch the exposed and unexposed group.
What is the definition of the preventable fraction?
The proportion of cases that would have occurred if people had not been exposed to a protective factor. This occurs when RR<1.
What is the definition of population attributable risk?
The excess risk of disease in the total study population. The number of cases that could be prevented if the risk factor was removed.
What are the equations used for PAR?
AR x Pe (proportion of exposed people in the population).
(Ipopulation- Iexposed)/ Ipopulation x100.
What is the equation for Par%?
P(RR-1)/P(RR-1) +1
What does Par% tell us?
The % of cases which could be prevented.
A big AR correlates with a big PAR? True or false?
False.
When will the same AR% give rise to a different population risk?
When the proportion of exposed individuals within a population changes.
What can the difference in means of different populations with a different distribution of a risk factor tell you?
The average effect of the environment and or lifestyle on the characteristic under study. Genetic differences are assumed to cancel out.
Are genetic variants greater between populations or within populations (most of the time).
Within populations.
What happens in a high risk intervention strategy?
Individuals at high risk are identified and treated.
What happens in an intervention strategy targeting a whole population?
The entire distribution of a risk factor within a population is shifted through addressing the underlying causes. This may not be beneficial is low values of a factor also result in a risk (eg too low a BMI).
Are high risk strategies or population strategies integrated with medical care?
High risk strategies.
Do high risk strategies or population strategies have a high benefit-to-risk ratio?
High risk strategies.
Do high risk strategies or population strategies offer a small contribution to the control of a disease?
High risk strategies.
Do high risk strategies or population strategies result in prevention being medicalised (which is a negative thing)?
High risk strategies.
Do high risk strategies or population strategies result in temporary and palliative success?
High risk strategies.
Do high risk strategies or population strategies offer a small individual benefit?
Population strategies.
What does the prevention paradox state?
That a large number of people exposed to a low risk generate more cases than a small number of people exposed to a high risk. A measure that brings large benefits to the community offers little to each participating individual.
