HSMG 643

End of Semester Project

1. An epidemiological investigation was begun on July 1, 2000 among a population of 1,000 individuals. Three individuals were found to have leukemia on July 1st. During the ten-year follow-up period, five new cases of leukemia were diagnosed. Among the eight leukemia cases, four deaths occurred during the ten-year follow-up period. Two additional individuals, neither of whom had leukemia, were lost to follow-up at some point during follow-up. The diagram below indicates the experience of the 10 study participants, using the following symbols:

* case recognition (diagnosis of leukemia)

*< onset of leukemia was prior to start of study period

—- observation period during follow-up

X status at termination of observation (i.e., alive, dead, lost)

None of the remaining 990 study participants became ill, died, or were lost to follow-up during the follow-up period.

D. What was the case fatality rate during the 10-year follow-up period?

1. What was the prevalence of leukemia on January 1, 2005?
   • What was the cumulative incidence of leukemia during the 10-year follow-up period?
   • What was the incidence rate of leukemia during the 10-year follow-up period?

Age Group(in years)	% of Population in Age Group			Heart Disease Rate per 100,000 person-years
	INDIA	U.S.A.	WORLD	INDIA	U.S.A.
< 30	60%	30%	50%	50	75
30-55	30%	40%	30%	80	150
>55	10%	30%	20%	120	400

Suppose that you want to compare the rate of heart disease in India to that in the United States. You know that age is an important risk factor for heart disease. Examine the age distribution of each country’s population.

1. A case-control study of dust lead levels and lead poisoning in children was conducted, Of the 200 cases of lead poisoning, 50 had high dust lead levels in their homes. Of the 200 controls, 30 had high dust lead levels in their homes.
   • What measure of comparison should be used to estimate the strength of the relationship between high dust lead level and lead poisoning?
   • Set up the two by two table and calculate this measure of comparison.
   • The 95% confidence interval for the measure of comparison was 0.8 to 3.0. Give your interpretation of this confidence interval.
2. Suppose that a study of oral contraceptive (OC) use and development of bacteriuria was conducted among 2,390 women, all of whom were initially free from bacteriuria. At the start of the study, the women were surveyed to determine whether or not they currently used OCs. 482 were using OCs and 1908 were not. By the end of the follow-up period, a total of 27 of the OC users and 77 of the non-users had developed bacteriuira.
   • Is this a cohort study or an experimental study?
   • Set up the two-by-two table for these data.
   • Calculate the risk ratio describing the strength of the relationship between OC use and bacteriuria.
3. Based on your answer above, do you think that OC users are at higher risk of developing bacteriuria than non-users?
   • The following table describes hypothetical age-specific rates of heart disease in India and the United States in 2009. Also included are hypothetical age distributions for the two countries and the entire world population.

Calculate the crude rate of heart disease for each of the two countries.

Should you use the two crude rates to compare the two countries? Why or why not?

Calculate an age-adjusted rate for heart disease in each country. Use the age distribution of the entire world as your standard.

C. race/ethnicity

1. Based on these answers, would you say that the age differences between India and the United States account for the entire difference in crude heart disease rates between the two countries?
   • Suppose that we undertake a cohort study to examine the association of high salt intake and hypertension. Our study population consists of male and female Hispanics and Caucasians. No matching or restriction is performed. Let’s assume that the following facts are true: Men consume more salt than women. Irrespective of their salt consumption, men have a greater risk of developing hypertension than women. Smokers consume the same amount of salt as non-smokers. Smoking is an independent risk factor for hypertension. Hispanics consume more salt than Caucasians. Irrespective of their salt consumption, Hispanics have the same risk of hypertension as Caucasians. Based on the above information, which of the following are likely confounders in this study? Justify your selection(s).
   • gender
   • smoking

What type of study is this?

1. A study followed 900,000 US adults from 1992 to 2008. At baseline, all participants were screened and determined to be cancer free and their body mass index (BMI) was calculated. Body mass index is a measure of obesity that is calculated using a person’s height and weight. Subjects were separated into the following groups according to their BMI: (a) normal weight, (b) slightly overweight, (c) moderately overweight and (d) greatly overweight. 57,145 deaths from cancer occurred in the population during the follow-up period.

The following results were seen for men and women when the heaviest members of the

cohort were compared to those with normal weight:

Men: Risk ratio of cancer death = 1.595% confidence interval = 1.1-2.1

Women: Risk ratio of cancer death = 1.695% confidence interval = 1.4-1.9

This study used self-administered mail questionnaires to gather data on height and weight in

1. State in words your interpretation of the risk ratio given for the men.
   • State in words your interpretation of the 95% confidence interval given for men. (Do not merely use the confidence interval to assess statistical significance.)
   • Are these results confounded by gender?

order to calculate the measure of obesity. Which of the following types of problems were

avoided by this method of data collection. Indicate Yes or No

A. Interviewer Bias

B. Exposure misclassification

C. Confounding

D. Selection Bias

E. Loss-to-follow-up