A cohort anion stud , y looked at the association between Were Hi g prisoners. There were 850 prisoners HIV positive and 21500 who were HIV negative in the study. The data from from the study are reported in table 4 below.
In this question provide all working for your calculation.
1. Calculate the rate ratio for all cause mortality to compare mortality by HIV status. [2 marks]
2. What was the (absolute) difference in mortality rates by HIV status? Interpret your answer. [2 marks]
3. Now calculate the proportion of deaths among prisoners that would have not occurred in the absence of HIV (the attributable fraction). Give an interpretation of your answer. [3 marks]
4. What is the overall incidence of mortality? [1 mark]
5. What would the incidence of mortality be if there was no HIV? [1 mark]
6. Using 4 and 5, calculate the population attributable risk. Interpret the population attributable risk. [2 marks]
7. Now calculate and interpret the population attributable fraction. [2 marks]
Question 2 [10 marks]
A cohort study looked at the association between level of alcohol consumption and hospital admissions and deaths related to alcohol (we will call these alcohol related events). Table 5 gives the number of alcohol-related events and the level of alcohol consumption.
Table 5: Cohort study data on level of alcohol consumption and alcohol-related events
Tables 6a and 6b gives the same data but stratified by socioeconomic status (low and high socioeconomic status).
Table 6: Cohort study data on level of alcohol consumption and alcohol-related events by socioeconomic status
(a) Low socioeconomic status
(b) High socioeconomic status
1. Calculate the appropriate measure of effect for the association between level of alcohol consumption and alcohol-related events. [2 marks]
2. Calculate the stratum-specific appropriate measures of effect. [4 marks]
3. Using 1 and 2 above, discuss whether socioeconomic status is a confounder or an effect modifier. [4 marks]
