Compute the crude death rates

Question

Course Learning Outcomes

A) Know about different measures of risk, how to calculate them and how this relates to understanding disease causation.

B) Calculate incidence rates of diseases within a population.

C) Understand the advantages and disadvantages of different types of epidemiological study designs and how these study designs can be applied to answer a research question.

D) Understand bias and confounding

E) Be able to perform age standardization.

Questions:

Question 1: A researcher is concerned about the mortality rate of older people in one small area of a city. She decides to compare the number of deaths in one year in this area with the number of deaths in two neighboring areas. The results are given in table 1.

Table 1: Number of deaths and number of people in three small areas of City S.

Age group	Area A		Area B		Area C
	Number of deaths	Number in Population	Number of deaths	Number in Population	Number of deaths	Number in Population
65-69	70	1,750	133	3,405	63	1,190
70-74	98	1,700	171	2,115	68	1,170
75-79	113	1,365	120	1,210	88	1,205
80-84	25	1,240	152	698	282	1,190
Total	306	6,055	576	7,428	501	4,755

a. Calculate the crude death rates (per 10,000 population) on each of the three areas. Interpret your results.

b. Use the direct method of age standardisation and area A as the reference population to estimate the age standardised rate of death per 10,000 population on areas A, B and C. Compare the death rates in the three areas.

c. Discuss the advantages and disadvantages of using age standardized rates instead of crude rates to compare death rates between populations. Consider both the direct and indirect method of calculating standardized rates. (No more than 180 words).

Question 2: In a study designed to explore the relationship between body mass index (BMI) and the risk of coronary heart disease, all men and women in a country born between 1960 and 1970 were sent a baseline lifestyle questionnaire in 2006. A total of around 250,000 subjects responded and were followed up for 11 years to assess their incidence of coronary heart disease (CHD). At the end of follow up in 2017, the following data were obtained.

Table 2: Gender, BMI and coronary heart disease.

Gender	BMI m/kg2	Coronary heart disease		Total
		Yes	No
Men	<25 (Normal)	288	29,346	29,635
	25-30 (Overweight)	833	62,346	63,179
	>30 (Obese)	1,410	31,910	33,321
	Total	2,532	123,603	126,135
Women	<25 (Normal)	417	46,506	46,923
	25-30 (Overweight)	577	47,776	48,353
	>30 (Obese)	808	28,173	28,981
	Total	1,801	122,455	124,256

a. What type of study design was used for exploring the relationship between BMI and coronary heart disease? What are the advantages of this study design?

b. Use an appropriate epidemiological measure to compare the incidence of CHD among women compared to men in this population. Interpret your results.

c. Calculate the incidence rate of CHD per 10 000 population among

i. those obese (>30 m/kg2)

ii. normal BMI (<25 m/kg2)

Interpret your results.

d. What percentage of cases of CHD among those obese in this population can be attributed to being obese compared to being of normal weight?

Question 3: The government of your country is concerned about the debate regarding the association between living close to electrical power lines and the incidence of childhood cancer. You have been asked to undertake a study to investigate this apparent association. Answer the following questions on the study you would conduct.

a. What are the aims and objectives of your study?

b. What type of study design would you choose and why?

c. How would you define and select the population(s) to include in your study?

d. How would you design your study and what methods would you use to measure the outcome and the exposure?

e. How would you analyze and interpret your results?

f. What are the potential sources of bias in your study, how would they affect your study and what steps would you take to minimize them?

g. What are the potential weaknesses and limitations of your study?