Chapter 8 Exercises  

8.1 Vitamins and neural tube defects (p. 169).  Link to full text of Milunsky et al., 1989. 

8.2 Framingham men (pp 169 - 170). 

8.3 CMV and restenosis (p. 170).

8.4 Cardiac arrest during high-intensity activity (p. 170).

8.5 Hepatitis B and liver cancer (fictitious data). A study of Hepatitis B infection and liver cancer found 65 cases of liver cancer in 65,000 person with Hepatitis B. In a Hepatitis-free cohort, there are 5 cases in 215,000 individuals. (A) Calculate the RR of liver cancer in this study. Interpret this statistic. (B) Calculate the RD. Interpret the results. [Units are required when interpreting rate differences.] (C) Which of the above statistics quantifies the strength of the association? Which quantifies the effect in absolute terms?

8.6  Stress hormones and coronary disease. Psychosocial stressors stimulate the secretion of catecholamines from the adrenal glands. As part of this stress response, catecholamines stimulate the sympathetic nervous system, constrict arteries, accelerates the heart rate, and increase cardiac ejection volumes. These may have deleterious effect on heart health. In a study was conducted to determine whether high levels of endogenous catecholamines increase the risk of coronary heart disease, 609 coronary heart disease free white males with high catecholamines levels had 76 coronary incidents. In contrast, 487  males with low catecholamines levels experienced, 44 incidents (Cassel, 1971). Calculate the relative risk of coronary disease associated with high catecholamine levels.  Interpret this finding.

8.7  John Snow. John Snow (1855) compiled the following information during his investigation of the 1854 cholera outbreak in London. Calculate the risk difference associated with the Southward & Vauxhall Company water source.

8.8 Joseph Goldberger. In 1918, Joseph Goldberger (1874 - 1929) wrote "of the 127 households owning cows which supplied milk during the three months preceding the date of the canvass in the spring of 1916, two ... were pellagrous; whereas of 451 not owning such cows, forty-seven ... had one or more cases of pellagra." Let "not owning a cow" be the risk factor. Calculate R₁, R₀, RD, and RR. Then show that RD = R₀(RR - 1).

8.9  Zocor. A randomized clinical trial evaluated the cholesterol-lowering drug Zocor on heart attack risk (4S Study Group, 1994). The treatment group of 2,221 subjects experienced 111 fatal heart attacks. The placebo group of 2,223 individuals experienced 189 such incidents. In relative terms, how much did the anti-hypercholesterolemic decrease risk? [Keep in mind that the baseline RR is 1.]

8.10 Cell phone use and auto accidents. One aspect of cell phone use that deserves our attention is its potential to cause driving accidents. Dreyer (1999) estimated fatal auto accidents rates of 5, 10, and 12 per 100,000 person-years for light, moderate, and heavy cell phones use. Using the light users as the reference category, calculate the risk differences associated with moderate and heavy cell phone use. 

8.11 Strong associations do not always effect a large number of people. An unspecified exposure is associated with two diseases: "disease 1" and "disease 2". Rates in exposed and nonexposed population per 100,000 person-years are reported in the table shown below.

(A) Calculate the RR of E for D1. Then calculate the RR of E for D2. For which disease does E have a stronger association? 

(B) Calculate the RD of E for D1. Also calculate the RD for D2. For which disease does E have the larger effect in absolute terms? 

(C) How do you explain the apparent paradox seen in analysis A and analysis B? [Hint: p. 164.]

8.12 In plain English. How would you explain each of these epidemiologic measures to a lay audience? (A) risk (B) relative risk (C) risk difference (D) attributable fraction in the population

8.13 Injuries in farm worker [similar to exercise 11.4]. McGwin et al. (2000) completed a cohort study in which various types of farmers were contacted biannually to determine if an agriculture-related injury had occurred. Results are shown here. Calculate the rates within each group. Then, determine RRs of injury using group 0 as the referent group. Is there an association between race and risk? Is there an association between farm ownership and risk? 

8.14 Vitamins and neural tube defects, population preventable fraction.  Take the data from exercise 8.1 and put in into a 2-by-2 table. Determine the proportion of neural tube defects [in the population] that would be averted with universal prenatal folic acid use. [Use either formula 8.17 or formula 8.18 to determine the preventable fraction.]

8.15 CMV and restenosis, attributable fractions. 

(A) Put the data presented in exercise 8.3 into a 2-by-2 table. Then, calculate the fraction of restenoses in CMV+ patients attributable to CMV. 

(B) Assume the data in exercise 8.3 are a random sample of all patients undergoing angioplasty. What fraction of the restenoses in the patient population is attributable to CMV? 

8.16. Why is it imprudent to say that a risk ratio of 10 indicates a high risk of disease in exposed people?

8.17 The rate ratio for an exposure and disease is 2 is two different populations. Does this suggest that the exposed groups in each of the populations have the same rate of disease?

Last edit: 04/02/2009
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