A study investigated the association between work in occupations likely to have involved exposure to asbestos and the occurrence of malignant Mesothelioma is a rare type of cancer that usually occurs in the chest cavity. Table 1 shows the data for carpenters (the exposed) and people working in occupations thought to be at low risk of asbestos exposure (the unexposed). Assume nearly all carpenters were exposed to asbestos.
Table 1: Association between profession and mesothelioma
Carpenter |
Mesothelioma |
Total |
|
Yes |
No |
||
Yes |
81 |
30 |
111 |
No |
25 |
278 |
303 |
Total |
106 |
308 |
414 |
- In this study, the appropriate measure to use to examine whether work as a carpenter (a proxy for exposure to asbestos) is associated with mesothelioma is an odds ratio. Can you explain why? [3 marks]
- What is the numerical value (the result) and interpretation of this measure? [2 marks]
- Can you calculate the attributable fraction? If so, calculate and If not, explain why not. [4 marks]
- Can you calculate population attributable fraction? If so, calculate and If not, explain why not. [4 marks]
Question 2 [27 marks]
A cohort study of people who were admitted to hospital for a stroke looked at the association between admission to hospital on weekdays (Monday to Friday) or the weekend (Saturday and Sunday) with in-hospital mortality. The data from the study are reported in Table 2 below. In this question, provide all working for your calculations.
Table 2: In hospital mortality, by admission period (weekday or weekend), among people admitted to hospital for a stroke
|
Deaths |
Number of people admitted |
Weekend admission |
2,467 |
23,297 |
Weekday admission |
5,929 |
70,324 |
Total |
8,396 |
93,621 |
- Calculate the risk ratio for in-hospital mortality to compare mortality by admission period. [2 marks]
- What was the (absolute) difference in mortality rates by admission period? Interpret your answer. [3 marks]
- Now calculate the attributable fraction associated with a weekend Give an interpretation of your answer. [3 marks]
- Calculate the population attributable risk for weekend Give an interpretation of your answer. [3 marks]
- Now calculate and interpret the population attributable fraction for weekend admissions. [3 marks]
- Summarise the findings from 1 to 5 in a [4 marks]
- What further information would you wish to know to assess the validity of your conclusions? [3 marks
The data are also available by age-group, with 2×2 tables for those aged < 65>
Tables 3a/b: In hospital mortality, by admission period (weekday or weekend), among people admitted to hospital for a stroke
- Age < 65>
|
Deaths |
Number of people admitted |
Weekend admission |
390 |
4,927 |
Weekday admission |
647 |
16,088 |
Total |
1,037 |
21,015 |
- Age ? 65 years
|
Deaths |
Number of people admitted |
Weekend admission |
2,077 |
18,370 |
Weekday admission |
5,282 |
54,236 |
Total |
7,359 |
72,606 |
- Calculate the stratum-specific risk [3 marks]
- Using 1, discuss whether age-group is an effect [3 marks]