Chapter 4 Review Questions

What was the case-fatality from cholera in 2010?

Case-Fatality Rate = Number of deaths from specific diseased during specified time ----------------------------------------------- Number of people with disease 30,000 deaths ------------------ 100,000 infected persons = 0.30 or 30%

Numbers of People and Deaths from Disease Z by Age Group in Communities X and Y COMMUNITY X COMMUNITY Y Age Group No. of People No. of Deaths from Disease Z No. of People No. of Deaths from Disease Z Young 8,000 69 5,000 48 Old 11,000 115 3,000 60 Calculate the age-adjusted death rate for disease Z in communities X and Y by the direct method, using the total of both communities as the standard population. The age-adjusted death rate from disease Z for community X is: ______

In order to calculate the age-adjusted death rate for disease Z in communities X and Y by the direct method, the total of both communities can be used as the standard population. This results in the following table: Expected number of deaths in Community X: = Expected number of deaths in young people in Community X + expected number of deaths in old people in Community X Expected number of deaths for young people in Community X:

In 1990, there were 4,500 deaths due to lung diseases in miners aged 20 to 64 years. The expected number of deaths in this occupational group, based on age-specific death rates from lung diseases in all males aged 20 to 64 years, was 1,800 during 1990. What was the standardized mortality ratio (SMR) for lung diseases in miners? ______

SMR = Observed deaths / expected deaths 4500/1800 = 2.5

The incidence rate of a disease is five times greater in women than in men, but the prevalence rates show no sex difference. The best explanation is that: a. The crude all-cause mortality rate is greater in women b. The case-fatality from this disease is greater in women c. The case-fatality from this disease is lower in women d. The duration of this disease is shorter in men e. Risk factors for the disease are more common in women

The best answer is b. Prevalence equals incidence times duration for a disease. If the prevalence rate shows no sex difference, but the incidence rate is five times greater in women than in men, then the duration of disease must be shorter in women. The duration of disease can be shorter for women either because the recovery rate is higher in women or the case-fatality rate is greater in women. Since there is no option discussing the recovery rate, then the correct statement is that the case-fatality rate is greater in women.

The mortality rate from disease X in city A is 75/100,000 in persons 65 to 69 years old. The mortality rate from the same disease in city B is 150/100,000 in persons 65 to 69 years old. The inference that disease X is two times more prevalent in persons 65 to 69 years old in city B than it is in persons 65 to 69 years old in city A is:

The best answer is b. The inference is incorrect because mortality data are presented for the two cities. Prevalence of a disease is typically a morbidity measure and does not represent the same concept as mortality. Therefore, the inference is incorrect because of the failure to distinguish between mortality and prevalence. The mortality rate is higher in city B, but it is incorrect to state that the prevalence is also higher in city B since the prevalence of the disease could be the same in the two cities with city B having a higher case-fatality rate.

The following are standardized mortality ratios (SMRs) for lung cancer in England: STANDARDIZED MORTALITY RATIOS Occupation 1949-1960 1968-1979 Carpenters 209 135 Bricklayers 142 118 Based on these SMRs alone, it is possible to conclude that: a. The number of deaths from lung cancer in carpenters in 1949-1960 was greater than the number of deaths from lung cancer in bricklayers during the same period b. The proportionate mortality from lung cancer in bricklayers in 1949-1960 was greater than the proportionate mortality from lung cancer in the same occupational group in 1968-1979 c. The age-adjusted rate of death from lung cancer in bricklayers was greater in 1949-1960 than it was in 1968-1979 d. The rate of death from lung cancer in carpenters in 1968-1979 was greater than would have been expected for a group of men of similar ages in all occupations e. The proportionate mortality rate from lung cancer in carpenters in 1968-1979 was 1.35 times greater than would have been expected for a group of men of similar ages in all occupations

The best answer is d. Standardized mortality ratios (SMRs) are useful for addressing whether a population, composed of workers in a certain industry, has higher mortality than would be expected if the population had the same mortality rate as those who do not work in the industry, i.e., in the general population. SMRs are computed by dividing the observed number of deaths by the expected number of deaths. This is typically referred to as an indirect method of age adjustment. When the ratio is greater than 1 (or 100 if multiplied by this amount to remove the decimal), then the inference is that the occupational cohort has a higher mortality rate than would be expected for a similar group of men of all ages who are representative of a wide range of occupations, not just carpentry. Answer a is incorrect since the SMR is a ratio and does not indicate the absolute number of deaths from lung cancer in either group. Answer b is not correct since the SMR indicates only the ratio between observed and expected lung cancer deaths. Neither the number of lung cancer deaths nor the number of total deaths in bricklayers is not provided, making the estimation of proportionate mortality impossible using this table. Answer c is incorrect because the lung cancer mortality rate cannot be inferred from the SMR. The ratio shown in the table expresses the proportion of observed to expected deaths in each period. Finally, answer e is incorrect since standardized mortality ratios are not directly comparable to proportionate mortality rates. Proportionate mortality is defined as the number of deaths from a particular disease divided by the total number of deaths. This requires knowing the absolute number of observed deaths due to lung cancer and the total number of all deaths in the group.

Annual Cancer Deaths in White Male Workers in Two Industries INDUSTRY A INDUSTRY B Cancer Site | No. of Deaths | % of All Cancer Deaths | No. of Deaths | % of All Cancer Deaths Respiratory system 180 33% 248 45% Digestive system 160 29% 160 29% Genitourinary 80 15% 82 15% All other sites 130 23% 60 11% Totals 550 100% 550 100% Based on the preceding information, it was concluded that workers in industry B are at higher risk of death from respiratory system cancer than workers in industry A. (Assume that the age distributions of the workers in the two industries are nearly identical.) 8. Which of the following statements is true? a. The conclusion reached is correct b. The conclusion reached may be incorrect because proportionate mortality rates were used when age-specific mortality rates were needed c. The conclusion reached may be incorrect because there was no comparison group d. The conclusion reached may be incorrect because proportionate mortality was used when cause-specific mortality rates were needed e. None of the above

The best answer is d. The data shown are for proportionate mortality defined as the number of deaths from a particular disease divided by the total number of deaths. Proportionate mortality is a proportion. It is not a rate so it cannot be used to make inferences about the risk of death in populations. In order to compare the risk of death from a specific cause in two groups, the cause-specific mortality rate must be used. This rate is a measure of risk in the populations. Only rates allow for inference about risk.

Age-adjusted death rates are used to: a. Correct death rates for errors in the statement of age b. Determine the actual number of deaths that occurred in specific age groups in a population c. Correct death rates for missing age information d. Compare deaths in persons of the same age group e. Eliminate the effects of differences in the age distributions of populations in comparing death rates Show Answer

The best answer is e. Mortality data are sometimes used to compare two or more populations. Sometimes populations may differ with regard to characteristics that may affect mortality. The most important factor that affects mortality is age. In order to compare death rates in two populations adjusting for the effect of age, several techniques have been developed. Therefore, the purpose of age-adjusted death rates is to eliminate the effects that differential age distributions between populations have when mortality rates are compared.

In an Asian country with a population of 6 million people, 60,000 deaths occurred during the year ending December 31, 2010. These included 30,000 deaths from cholera in 100,000 people who were sick with cholera. 1. What was the cause-specific mortality rate from cholera in 2010?

The number of deaths from a specific cause ------------------------------------------------ the number of people in the population = 30,000 ------------ 6,000,000 = 0.005 or 5 deaths per 1,000 people

For a disease such as pancreatic cancer, which is highly fatal and of short duration: a. Incidence rates and mortality rates will be similar b. Mortality rates will be much higher than incidence rates c. Incidence rates will be much higher than mortality rates d. Incidence rates will be unrelated to mortality rates e. None of the above

a.

A program manager from an international health funding agency needs to identify regions that would benefit from an intervention aimed at reducing premature disability. The program manager asks a health care consultant to develop a proposal using an index that would help her make this decision. Which of the following would best serve this purpose? a. Case-fatality b. Crude mortality rate c. Disability-adjusted life-years d. Standardized mortality ratio

c.