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Epidemiology 6000 1. In which of the following measures is the numerator not included in the denominator? a. Proportion b. Ratio c. Rate d. Incidence 2. Which of the following measures includes the element of time? a. Proportion b. Ratio c. Rate d. Cumulative incidence 3. Compare and contrast cumulative incidence and incidence density. Cumulative incidence is a proportion with the population at risk of developing the disease as the denominator. All participants in the study must complete the entire follow-up period. Incidence density is a rate with person-time for the denominator. You can still calculate incidence density if people drop out of the study before the end of the follow-up period. Both have the number of new cases in the numerator. You must exclude prevalent cases from the numerator in both measures. Both measure the risk of developing a disease. 4. Which of the following measures the relative impact of premature death on society and can be used to establish public health priorities? a. Age-specific death rate b. Years of potential life lost c. Case fatality rate d. Crude death rate 5. Why do we use person-time?

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Not all participants will be in the study for the same length of time. Follow-up times will vary among individuals because subjects enter the study at different times, die, move, or they drop out, etc. Person-time allows us to calculate incidence when all subjects do not complete the entire follow-up period. 6. What are some of the problems with using crude rates instead of adjusted rates? Usually it is difficult to compare crude rates between groups, because each group may have different distributions of underlying characteristics (e.g. age, gender) that are associated with the risk of developing the disease. You must standardize so the two groups have comparable distributions of these characteristics. 7a. Calculate the expected deaths for Miami and Alaska using the U.S population in Table 2 as the standard population. 7b. Calculate the direct adjusted death rates for Miami and Alaska in Table 1. Are the adjusted rates the same or different? Table 1 Miami Alaska Age Population Death Rate/1000 Expected Deaths Population Death Rate/1000 Expected Deaths <15 114,350 1.199 ? 37,164 1.59 ? 15- 24 80,259 0.71 ? 20,036 0.90 ? 25- 44 133,440 1.56 ? 32,693 1.13 ? 45- 64 142,670 7.12 ? 14,947 6.02 ? 65+ 92,168 39.11 ? 2,077 39.00 ? Total 562,887 ? 106,917 ? Table 2 Age U.S. population in thousands Deaths in thousands Rate/1000 <15 23,961 32 1.34 15- 24 15,420 9 0.58 25- 44 21,353 30 1.40 45- 64 19,609 140 7.14 65+ 10,685 529 49.51
Total 91,028 Miami expected deaths; < 15: 23.961/1,000 x 1.199 = 29 15-24: 15,420/1,000 x 0.71 = 11 25-44: 21,353/1,000 x 1.56 = 33 45-64 19,609/1,000 x 7.12 = 140 65+: 10,685/1,000 x 39.11 = 418 Total: 631 Miami age-adjusted death rate = (631/91,028) x 1000 = 6.93/1000 Alaska expected deaths: <15: 23,961/1,000 x 1.59 = 38

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