EPIDEMIOLOGY
Question 1
For each of the following excerpts, indicate which of the criteria for causation (proposed by Bradford Hill, 1965).
i) [From a study of preconception paternal x-ray exposure and birth outcome] "The exposure variable was generated from an item on the partner's questionnaire asking about specific medical x-ray studies performed anytime within 12 months preceding conception."
ii) [From a study of predictors of gallbladder disease in men] "Higher level of BMI (body mass index) were progressively associated with increased risk of diseases, and men with BMI > = 24.0 units had a significant, 46 percent increased risk when compared with their counterparts with BMI <20.0".
Question 2
As an epidemiologist, you may wish to compare the mortality rates among individuals living in two different cities, i.e., Mayhemberg and Lazyaces. The age distribution and age-specific deaths of these cities are shown below:
|
|
Mayhemberg
|
2012
|
Lazyaces
|
2012
|
|
Age group
|
Population
|
Age-specific deaths
|
Population
|
Age-specific deaths
|
|
|
|
|
|
|
|
0 - 54
|
50000
|
05
|
150000
|
08
|
|
55 - 74
|
7500
|
25
|
60000
|
100
|
|
≥ 75
|
2500
|
35
|
40000
|
250
|
|
|
|
|
|
|
i). Calculate the crude and age specific death rates per 10000 population for the two communities. Compare the results.
ii) If you wish to standardise the death rates, would you use Direct or Indirect means of doing so? Justify your choice.
iii) Use the appropriate method of standardisation to determine whether city Mayhemberg has a higher death rate compared to the city Lazyaces. Comment on your result.
** For all calculations, use up to 2 decimal point.
Question 3
For each of the following, determine whether it is more closely related to incidence or prevalence.
i) Number of participants who developed gastroenteritis within a few days after eating salad at the conference dinner.
ii) Number of persons who died and whose deaths were attributed to Tsunami in Aceh province, Sumatra, Indonesia in 2004.
iii) Number of children who has immunisation to chicken pox, either because they had the disease or because they received the vaccine.
Question 4
The following data were obtained in a study in which 1000 individuals were followed for 20 years to examine the hypothesis that chronic arsenic exposure through drinking water increases the risk for skin cancer.
|
Exposure status
|
Cancer
|
No cancer
|
Total
|
|
Arsenic exposed
|
30
|
470
|
500
|
|
Unexposed
|
11
|
489
|
500
|
|
Total
|
41
|
959
|
1000
|
i) Estimate the number of person-years contributed by the unexposed group.
ii) What is the 20-year risk of skin cancer among those who were chronically exposed to arsenic in drinking water?
iii) What is the prevalence of skin cancer among the unexposed group?