Comparative Analysis of the Effectiveness of Drug in Lowering Blood Pressure

The assignment content discusses the effectiveness of a drug in lowering blood pressure and its stratification by weight status. The results show that the drug is more effective in individuals with normal body mass index (BMI) than those who are overweight. Additionally, it covers various biases such as selection bias, confounding, and measurement bias, along with practical ways to avoid them.

Running head: EPIDEMOLOGY
EPIDEMOLOGY
Name of the Student
Name of the university
Author’s note

1EPIDEMOLOGY
Question 1:
Source:
Sundquist, K. Qvist, J. Johansson, S. Sundquist, J. “The long-term effect of physical activity on
incidence of coronary heart disease: a 12-year follow-up study”
(a) “What study design does this study employ”? [1 point]
Ans- The current study uses a cohort design.
(b) “Find the methodological aspects mentioned in the paper that convinced you that is the
type of study design, please use dot points” [2 points]
 The sample population has been divided into several groups like those who are smokers,
those who had a history of smoking more than 14 cigarettes a day, the long term smokers,
the ones smoking 1-14 cigarettes daily, and those who have never smoked.
 The population was divided into male and female and the level of income was divided
into high and low income categories.
 The physical activity leisure time was divided into – No exercise, exercise on an
occasional basis, exercise about two times a week, twice a week undertaking vigorous
exercise.
 These are for the assessment of CHD risks in the population, which shows that the study
design is a cohort one.

2EPIDEMOLOGY
(c) “What justification do the authors give for conducting this study, please use dot
points”? [2 points]
For analysis of long term effect of the leisure time physical activity on CHD cases.
 To examine the impact of, SES, sex, age , smoking and BMI on the development of
CHD.
(d) “What was the proportion of those who (i) do not do any physical activity (ii) engaged
in twice a week vigorous physical activity”?
Ans- i) Physical activity was not done by 9% of the population.
ii) 42.3% of the sample population had taken part in vigorous activities twice a week.
(e) “What is the crude incidence rate of CHD in inactive men and inactive women”? [2
points]
Ans- the rate of occurrence of CHD in inactive men and inactive woman are 111 and 38 per
10,000 person years respectively.
(f) “What is the crude relative risk of being non-active versus being “highly active”
(vigorous physical activity at least twice a week) in men and in women” [2 points]
Ans: Hazard ratio
Non active- 1
active highly- 0.50 (0.31-0.80) (HR with 95% confidence intervals).

3EPIDEMOLOGY
(g) “How would you interpret the relative risk in the above section” (f)? [2 marks]
Ans: - The mentioned data above shows that an increase in the amount of the physical activity
leisure time can reduce CHD risk. The mechanism linking CHD to physical activity is that,
physical activities lowers the blood pressure. Level of lipids, plasma viscosity, Plasma fibrinogen
decrease.
(h) “Looking at the sex and age adjusted RR in Table 3 (the RR is measured by the
Hazard Ratio which is similar) (i) how would you describe the association between physical
activity and CHD” [4points]
Ans:- Table 3 shows that participants who had performed leisure time physical activity after
adjustment for sex and age showed a 54% lower risk of developing CHD than the ones without
performing leisure activity. It was also seen that the ones who occasionally performed physical
activity in leisure time exhibited a lowered risk of developing CHD. It has also been showed that
people with less income, people with high BMI current smokers and indicated an increased
developmental risk of CHD. (79)
(i) “The authors removed from the analysis any person who self-rated their health as “bad”
or “anywhere between good and bad” why? (One sentence [2 points]
Ans: - the self rated participants themselves or anywhere between good and bad or in bad health
were excluded to prevent any biasness and were considered as poor self rated health.

4EPIDEMOLOGY
(j) “What possible bias could have changed the estimate for the association between
physical activity and CHD – mention at least one, and explain why” [2 points]
Ans: - One of the bias that affects the estimate between CHD and physical activity is that , most
of the questionnaire has been made to keep a record the leisure time activity, which do not
include the physical exercise due to household activities or occupational activities, which can
give a false negative result.
(j) “Do you think this research adequately addressed confounders? Justify your answers
{no more than 60 words}” [2 points]
(Ans) Yes, this research perfectly addressed the confounders. The confounders in this research
study are the income, smoking and the BMI. These researches had shown the effects of physical
activity in the development of CHD, in presence of these factors and the results obtained are
influenced by these factors. The different models have been adjusted for physical activity,
smoking, sex, age, income and BMI.
Question 2:
“Researcher wanted to know whether there is an association between use of certain drug
(Reserpine) and breast cancer. Their target population was 2 million women, 1 million from low
socio-economic status (SES) and 1 million from high SES. The prevalence of breast cancer in
this population and the use of Reserpine is documented bellow”

5EPIDEMOLOGY
High SES Low SES
Breast cancer prevalence 20 per 100,000 20 per 100,000
Resperine 800 per 10,000 200 per 10,000
a) What is the study design, justify? [2 Points]
(Ans) This is a cohort study which deals with the population of 2 million woman having different
socio economic status and who have taken Reserpine and those who have not taken Reserpine.
b) “Build the 2X2 table consist with data above. To be able to fill in the cells you have to
assume that there is no association between the use of Reserpine and breast cancer. In
other word the prevalence of breast cancer is similar among drug users and non-drug users
and this is true in both high and low SES. Hint: to help you fill in the data you must start
with the number that appears in the Table marginal total columns and rows”. [4 points]

6EPIDEMOLOGY
High SES Low SES
Breast
Cancer
No
breast
cancer
Total Breast
Cancer
No
breast
cancer
Total
Use
Reserpine.
16 79984 80,000 4 19996 20,000
Non-users
of
Reserpine
184 919816 920,000 196 979804 980,000
Totals 200 999,800 1,000,00
0
200 per
1000000
200 per
1000000
1,000,000
“Now assume that the association with Reserpine was evaluated in a follow up study and the
investigators found that the incidence rate of breast cancer among women who used Reserpine
was 3 times higher than among women who did not use Reserpine. Stratum specific analysis
showed that this was true for both high and low SES”.
“If Reserpine is causally related to breast how many cases of breast-cancer could be avoided in
the high SES and Low SES had Reserpine would be banned from being in the market? (In other
words what is the PAF?)” [3 points]
(Ans): Assuming the above mentioned fact, the table can be updated as:

7EPIDEMOLOGY
Breast Cancer No breast cancer Total
Use Reserpine. 552 79448 80,000
Non-users of Reserpine 184 919816 920,000
Totals 736 999,264 1,000,000
R.R=
552
80,000
184/920000
=345
P.A.F=
80,0000
92,0000 (345−1)
80,000
92,0000 ( 345−1 ) +1
=0.96
Interpretation:
96% of the women consuming reserpine are attributed to breast cancer as per the assumptions
given.

8EPIDEMOLOGY
Question 3
“A new drug to lower blood pressure (BP) is being tested. The results of the RCT are
displayed below”:
Exposure
“There was a speculation, that the drug may not be as effective in overweight individuals as in
normal weight. The results was stratified by weight status and are presented bellow”
Over-weight Normal weight
BMI >= 25 BMI <25
Lowered
BP
No change
in BP
Lowered
BP
No change
in BP
Drug 30 20 Drug 40 10
Lowered
BP
No change
in BP
Drug 70 30 100
Placebo 40 60 100

9EPIDEMOLOGY
Placebo 20 30 Placebo 20 30
a) “Calculate the stratum specific association between the drug and blood pressure [2
points]”
Ans: - The stratum specific risk ratios are as follows:-
Among those with BMI>=25, the risk ratio is:
RR= 30/50
20/50 = 1.5
Among those with BMI< 25, the risk ratio is:
RR= 40/50
20/50 = 2
b) “Calculate the crude measure of association between the drug and blood pressure [2
points]”
(Ans) It has to be kept in mind that the risk ratio for a combined total, sample was RR= 1.79, this
is the crude measure of association and is not adjusted for confounding factors. The risk ratio
among those with BMI greater than 25 is less than the standard crude ratio. Again the risk ratio
in those with less BMI is higher than the standard crude ratio.

10EPIDEMOLOGY
c) “Interpreted your findings [2 points]”
Ans: - The finding shows that the speculation has been right, as it can be clearly seen from
the risk ratio that the persons having normal body mass index is having greater risk ratio of
lowered BP, than in the obese persons, which shoes that the drug is more effective in case of
persons with normal body weight.
Question 4
“A case –control study was carried out in which 120 of 200 people with type 2 diabetes and 50
out of 200 control people reported a history of sleep –disorders breathing. In further analysis, the
investigators noticed that 50% of the cases but only 25% of the controls were men. Could this
difference induce a bias? Explain your answer. What would be a practical way to avoid such
differences in case control studies?” [4 points]
(Ans) The following differences can induce a bias as, consideration of more number of men as
control might have altered the results. It can be considered as the observational selection bias.
Sampling bias can be reduced by taking the following measures:-
1. To convenience sampling or judgment.
2. To ensure that the sample frame matches it as much as possible and the target
population is properly defined and the.

11EPIDEMOLOGY
Question 5
“Which of the following terms associated with selection bias? [2 points]”
a) Chance.
b) Confounding.
c) Response rate
d) Validity
“Explain your choice in one sentence”
Ans: - Confounding is the term that is associated with selection bias. Confounding can contribute
to the overestimates or underestimates of an intervention and lead to type I and type 2 errors.
(34)
Question 6
“Which of the following term is associated with measurement bias? [2 points]”
a) Effect Modification
b) Confounding.
c) Response rate
d) Validity
“Explain your choice in one sentence”
Ans: - Response rate is associated with measurement bias. Response rate can give rise to
measurement bias if the non response is unequal among the participants regarding outcome.
Then it can be termed as a non responsive bias.

12EPIDEMOLOGY
Question 7
“What biases would you suspect in a survey of the prevalence of drug use among young people
using a representative sample of students attending high school justify (not enough to name the
biases (No more than 60 words)” [4 points]
(Ans) A non response bias can supposedly occur while monitoring adolescent population for
monitoring certain heath indicators. Non response bias occurs when some of the respondents in a
particular sample do not respond. Since usage of drug is a confidential matter for the students
and many would not like to respond openly to this. Hence, errors might come from the absence
of respondents. This can cause a variation between the true mean values of the original sample
and the net sample.

13EPIDEMOLOGY
References
Eom, C.S., Park, S.M. and Cho, K.H., 2012. Use of antidepressants and the risk of breast cancer:
a meta-analysis. Breast cancer research and treatment, 136(3), pp.635-645.
Sundquist, K., Qvist, J., Johansson, S.E. and Sundquist, J., 2005. The long-term effect of
physical activity on incidence of coronary heart disease: a 12-year follow-up study. Preventive
medicine, 41(1), pp.219-225.