Foundations of Epidemiology Questions - needing help.

1. Investigators were interested in examining the effect of air pollution on the incidence of stroke. They conducted a cohort study enrolling 61,285 adults aged 55 years and older who had no evidence of a previous stroke at baseline. Baseline was the time they enrolled into the study. Air pollution measures included exposure to fine particulate matter collected from the residences of participants and this was categorised into high and low average exposure over the study. The cohort was followed over 20 years and 431 cases of stroke occurred. The investigators found a relative risk of stroke among those exposed to high levels of particulate matter of 1.47. What percentage of stroke cases among study participants exposed to high air pollution levels was attributable to that exposure?

What percentage of stroke cases among study participants exposed to high air pollution levels was attributable to that exposure?

A. 68.0%

B. 79.0%

C. 0.70%

D. 32.0%

2. The age-standardised incidence of liver cancer in a hypothetical population is 4.6 per 100,000 population. In the same hypothetical population, the prevalence of any lifetime risky drinking (exceeding national guidelines) is estimated to be 38%. Excessive alcohol consumption is a risk factor for development of liver cancer. The incidence of liver cancer was 6.9 per 100,000 population among those reporting any lifetime risky drinking and the incidence in those not reporting any lifetime risky drinking was 3.6 cases per 100,000 population.

What is the risk of liver cancer that can be attributed to risky alcohol consumption among those who reported risky drinking?

A. 3.3cases of liver cancer per 100,000 populationof risky drinkers

B. 47.8% of the cases ofliver cancerin the populationof risky drinkers

C. 2.3cases of liver cancer per 100,000 populationof risky drinkers

D. 1.9cases of liver cancer per 100,000 populationof risky drinkers

3. Approximately 1 in 6 men over the age of 65 will experience prostate cancer. Given the advances in chemotherapy a large proportion of men are expected to survive. There is emerging evidence that men who survived prostate cancer have an increased risk of stroke compared to those without prostate cancer. Investigators were interested in understanding the effect of prostate cancer on the risk of developing stroke in this patient group. They conducted a 15-year cohort study and recruited 2,163 men aged at least 65 years, free of prostate cancer and cardio-vascular disease at the start of follow-up.

The participants who did not develop prostate cancer during follow-up contributed 18,662 person-years at risk over the study period. The participants who reported a prostate cancer during the follow-up contributed 4269 person-years at risk over the study period. During the study follow-up, 596 participants developed stroke, including 127 cases occurring in those with prostate cancer.

What is the relative risk of stroke among study participants with prostate cancer compared to those without prostate cancer?

A. 1.18

B. 4.60

C. 0.84

D. 1.14

4. Approximately 1 in 9 women over the age of 50 will experience breast cancer. Given the advances in chemotherapy a large proportion of women are expected to survive. There is emerging evidence that women who survived breast cancer have an increased risk of stroke compared to those without breast cancer. Investigators were interested in understanding the effect of breast cancer on the risk of stroke in this patient group. They conducted a 15-year cohort study and recruited 5,526 women aged at least 50 years, free of breast cancer and stroke at the start of follow-up.

The participants who did not develop breast cancer during follow-up contributed 50,269 person-years at risk over the study period. The participants who reported a breast cancer during the follow-up contributed 12,238 person-years at risk over the study period. During the study follow-up, 1102 participants had a stroke, including 300 cases occurring in those with breast cancer.

What percentage of stroke cases among study participants with breast cancer was attributable to having breast cancer?

A.34.9%

B.28.1%

C.6.9 cases per 1,000 person-years

D.8.6 cases per 1.000 person-years

5. Among women aged 15-49 years, the prevalence of use of oral contraceptives (OC) is 21% of the general population. Investigators were interested in understanding the effect of initiating OC use on the subsequent risk of developing deep vein thrombosis (DVT) and conducted a cohort study. The study included 7,863 women aged 15-49 years who were followed for 5 years. During the 5-year study period, 360 women were diagnosed with DVT, including 206 who had initiated OC use since the beginning of the study period. At follow-up, women who had initiated OC use had contributed 18,945 person-years and those who had not initiated OC use had contributed 20,370 person-years of follow-up.

What was the excess risk of DVT among OC users attributable to the use of OC in the study?

A. 3.3 cases of DVT per 1,000 OC users per year

B. 15.8cases of DVT amongOC users

C. 1.7cases of DVT per 1,000OC usersper year

D. 30.5% ofcases of DVTamongOC users