Homework answers / question archive / Jefferson College of Population Health PBH 506 Fundamentals of Epidemiology Fall 2020 Problem Set #2 (50 points): Please type your answers and highlight your response

Jefferson College of Population Health PBH 506 Fundamentals of Epidemiology Fall 2020 Problem Set #2 (50 points): Please type your answers and highlight your response

Health Science

Share With

Jefferson College of Population Health PBH 506 Fundamentals of Epidemiology Fall 2020 Problem Set #2 (50 points): Please type your answers and highlight your response. Show your calculations whenever appropriate. Upload your document (must be compatible with Microsoft word) on Canvas AND to the Problem Set #2 Quiz portal. You may work with others on the Problem Set. You may work with others on the Problem Set. For each question on which you worked with someone else, please note your collaboration. Use the following information to answer questions 1-2. There were 250 students enrolled at the Kip City Public School at the beginning of the 2015-2016 school-year. At the beginning of the year, school nurse records indicated that 42 of the students had asthma. During the school year (September 1 through June 30), 18 additional children were reported to have a diagnosis of asthma. No children were enrolled in the school or left the school during the school year. You can assume that an asthma diagnosis is permanent, so once a child is diagnosed, they are never cured. 1. (2 points) What was the baseline prevalence rate of asthma in this population at the beginning of the school year? 2. (3 points) What was the incidence rate for asthma in this population during the school year? Questions 3-6: An investigation of disease registries identified the following heart disease mortality data among two different (fictitious) cities in Pennsylvania (Quartz City and Zachary) in the year 2015: Quartz City Group Age (years) Total Population Deaths 1 2 3 4 5 0 to 4 5 to 14 15 to 19 20-59 60+ 1500 600 300 900 150 370 89 70 70 43 Zachary Group Age (years) Total Population Deaths 1 2 3 0 to 4 5 to 14 15 to 19 400 600 500 70 100 100 Age-specific Death Rate Age-specific Death Rate 1 4 5 750 650 20-59 60+ 120 170 3. (3 points; Please fill in table above) What are the age-specific mortality rates for Quartz City and Zachary (per 100 population)? 4. (2 points) What are the crude mortality rates, overall, for Quartz City and Zachary (per 100 population)? 5. (2 points) How do the rates compare between Quartz City and Zachary? Why might the use of crude mortality rates not be a good way to compare death rates between Quartz City and Zachary? 6. (3 points) Given what you know about the health influences of population-based characteristics of person, place, and time, provide 3 possible explanations for the differences (or similarities) of rates between Quartz City and Zachary. Table 1 below describes the morbidity of disease X in two populations stratified by age: Age Population A Number with Disease (n) Number in Population (N) Population B Number with Disease (n) Number in Population (N) < 18 13 10,000 47 35,000 18-35 26 15,000 23 20,000 36-65 29 25,000 25 22,000 > 65 54 30,000 47 18,000 7. (2 points) What are the crude morbidity rates, overall, for Population A and Population B (per 100000)? 8. (1 point) What is the crude morbidity rate among 18-65 year olds in Population B (per 100000 population)? Table 2 is just like table above, but also provides information on a reference population stratified by age categories. Population A Age Reference Number Population with Disease Number in Population Population B Expected in Population A Number with Disease Number in Population Expected in Population B 2 < 18 25,000 13 10,000 47 35,000 1835 3665 > 65 25,000 26 15,000 23 20,000 25,000 29 25,000 25 22,000 25,000 54 30,000 47 18,000 9. (5 points) Using Table 1 and Table 2, find the age-adjusted morbidity rates for Population A and Population B using the direct age-standardization process. How do the adjusted rates compare between Population A and Population B? Please explain your answer. Use the following information for question #10. The table below provides information about the rates of morbidity due to an emerging infectious disease (named DOSx) in a reference population stratified by age group, and also the number of residents in Population C stratified by age group. Also, you know that the total number of people who acquired DOSx in Population C was 89. Age Rate of Number Group Disease in with Reference Disease Population Population C Number in Expected Population Disease # in Population < 18 38/10,000 -- 10,078 18-35 13/10,000 -- 24,564 36-65 26/10,000 -- 22,998 > 65 35/10,000 -- 43,090 10. (4 points) Calculate and interpret the Standardized Incidence Ratio (SIR) for DOSx in Population C. 11. (4 points) How and why do mortality and morbidity differ by sex? Explain and relate your discussion to the female paradox, and discuss both genetic and environmental factors. Please limit your answer to 2 paragraphs. 12. (4 points) If John Snow were to conduct his study of cholera deaths in present day time, where could he get cholera morbidity and mortality data? List two possible secondary data sources (one for mortality data and one for morbidity data) and be as specific as possible. Please limit your answer to 2 paragraphs. 13. (4 points) You are interested in reducing obesity among teenage girls aged 12-17. Describe one primary prevention approach and one secondary prevention approach you would 3 use. Make sure to convey your understanding of the difference between primary and secondary approaches, and be specific about defining your population. Please limit your answer to 2 paragraphs. Multiple Choice (1 point each) 14. When analyzing public health data, an abrupt drop in mortality due to a specific disease from one year to the next is most likely due to: A. incorrect listing of cause of death by the physician on the death certificate B. coding mistake by nosologists when using the International Classification of Disease (ICD) system C. A and B D. a change in the International Classification of Disease (ICD) system E. fewer older persons dying from chronic diseases each year 15. Cyclic variations in the occurrence of disease may reflect: A. Changes in exposure to infectious agents B. Changes in the risk-taking behavior of persons C. Changes in temporary stressors D. Endogenous biologic factors E. All of the above 16. Cautious use of information from death certificates is warranted because: A. certificates are not available for everyone who dies in the U.S. B. certificates are often erroneous for date of death and sex C. cause of death information may not be correct D. autopsy results are not included E. all of the above 17. Large international variations in rates of infectious and communicable diseases as well as other conditions are likely explained by: A. differences in climate B. differences in cultural factors C. national dietary habits D. access to health care E. all of the above 18. Which of the following data sources is most likely to provide a representative sample of the general health status of a population? A. hospital outpatient statistics B. absenteeism data C. data from public health clinics D. a cross-sectional morbidity survey of the general population E. electronic medical records, supplemented with interviews 19. What is one of the widely used sources of statistical data on cancer? 4 A. B. C. D. Disease registries Vital statistics Special survey apportionments Hospital clinic statistics 20. High rates of mortality from hypertension found among African Americans may be due to: A. Dietary factors B. Exposure to stress C. Lack of social support D. Obesity E. All of the above 21. The Vital Statistics Registration System in the U.S. collects data on all vital events including: A. births B. deaths C. fetal deaths D. A and B only E. A, B, and C 22. Descriptive epidemiology characterizes the amount and distribution of disease within a population and enables the researcher to: A. make direct tests of etiologic hypotheses B. generate testable hypotheses regarding etiology C. evaluate trends in health and disease within a population D. all of the above E. B and C only 23. A null hypothesis is most similar to which of the following? A. Positive declaration B. Negative declaration C. Implicit question D. Mill’s canon of neutrality 24. At Thomas Jefferson University, new employees need to get 5 screening tests as part of the new employee health examination to detect various diseases. What is the name for this type of screening program? A. Selective screening B. Mass screening C. Ad hoc screening D. Multiphasic screening 5 Measures of Morbidity and Mortality III PBH 506 Fundamentals of Epidemiology Allison R. Casola, PhD, MPH, CHES ARC 1 Measures of Disease: Prevalence v. Incidence • Incidence = new cases • # new cases/ #people at risk in given time frame • Rate • Measuring how fast the disease is occurring = risk • Prevalence = all cases (in total) • # cases/# total people • Proportion, aka a percentage • How much disease is in the population? = burden of disease Ratio v. Proportions v. Rates • Ratio: relationship between two numbers • Ex: males/females • Proportion: ratio where numerator is included in the denominator • Ex: males/total births • Rate: proportion with specification of time • Ex: (deaths in 2020/population in 2020) x 1,000 Crude Rates • Use crude rates with caution when comparing disease frequencies between populations. • Observed differences in crude rates may be the result of systematic factors (e.g., sex or age distributions) within the population rather than true variation in rates. Specific Rates • Specific rates refer to a particular subgroup of the population defined in terms of race, age, sex, or single cause of death or illness. • Specific rates and crude rates are not mutually exclusive. (Rates can be specific AND crude). Cause-Specific Rate Example: Cause-specific mortality rate due to unintentional drowning in U.S. 2003 = 354/203,872,598= 1.7 deaths per 1,000,000 Proportionate Mortality Example: PMR (%) for HIV among the 25- to 34-year-old group = 1,588/41,300 = 3.8% Indicates relative importance of a specific cause of death; not a measure of the risk of dying of a particular cause. Age-Specific Rate (Ri) 9 Method for Calculation of Age-Specific Death Rates ARC 10 Measures of Morbidity and Mortality III PBH 506 Fundamentals of Epidemiology Allison R. Casola, PhD, MPH, CHES ARC 13 Measures of Morbidity and Mortality I PBH 506 Fundamentals of Epidemiology Allison R. Casola, PhD, MPH, CHES ARC 1 Learning Objectives • Define and distinguish among ratios, proportions, and rates • Define the terms prevalence and incidence • Explain the term population at risk ARC 2 Overview of Epidemiologic Measures ARC 3 Count • The simplest and most frequently performed quantitative measure in epidemiology. • Refers to the number of cases of a disease or other health phenomenon being studied. ARC 4 Examples of Counts • Cases of influenza reported in Warminster PA, during January of a particular year. • Number of bicyclists riding down the street without helmets • College dorm students who had mono ARC 5 Ratio • The value obtained by dividing one quantity by another. • Consists of a numerator and a denominator. • The most general form has no specified relationship between numerator and denominator. • Rates, proportions, and percentages are also ratios. ARC 6 Example: Simple Sex Ratio Calculation • A ratio may be expressed at = X/Y • Simple sex ratio • Of 1,000 motorcycle fatalities, 950 victims are men and 50 are women. Number of male cases Number of female cases ARC = 950 50 = 19:1 male to female 7 Example: Demographic Sex Ratio Calculation • This ratio refers to the number of males per 100 females. In the U.S., the sex ratio in 2010 for the entire population was 96.7, indicating more females than males. Number of males Number of females ARC X 100 = 151,781,326 156,964,212 X 100 = 96.7 8 Definition of Proportion • A measure that states a count relative to the size of the group. • A ratio in which the numerator is part of the denominator. • May be expressed as a percentage. ARC 9 Uses of Proportions • Can demonstrate the magnitude of a problem. • Example: 10 dormitory students develop mono. How important is this problem? • If only 20 students live in the dorm, 50% are ill. • If 500 students live in the dorm, 2% are ill. ARC 10 Example of a Proportion • Calculate the proportion of African-American male deaths among African-American and white boys aged 5 to 14 years. ARC 11 Rate • Definition: a ratio that consists of a numerator and a denominator and in which time forms part of the denominator. • Contains the following elements: • disease frequency • time period • unit size of population ARC 12 Example of Rate Calculation Crude death rate = Number of deaths in a given year Reference population (during the midpoint of the year) X 100,000 Example: Number of deaths in the United States during 2007 = 2,423,712 Population of the U.S. as of July 1, 2007 = 301,621,157 Crude death rate = 2,423,712 301,621,157 = 803.6 per 100,000 Definition of Prevalence • The number of existing cases of a disease or health condition in a population at some designated time. ARC 14 Figure 3-1: Analogy of prevalence and incidence. The water flowing down the waterfall symbolizes incidence and water collecting in the pool at the base symbolizes prevalence. Interpretation of Prevalence • Provides an indication of the extent of a health problem. • Example 1: Prevalence of diarrhea in a children’s camp on July 13 was 15. • Example 2: Prevalence of obesity among women aged 55-69 years was 367 per 1,000. ARC 16 Uses of Prevalence • Describing the burden of a health problem in a population. • Estimating the frequency of an exposure. • Determining allocation of health resources such as facilities and personnel. ARC 17 Point Prevalence Point Prevalence = Number of persons ill Total number in the group at point in time Example: Total number of smokers in the group = 6,234 = 149.0 per 1,000 Total number in the group 41,837 or 14.9% ARC 18 Period Prevalence Period Prevalence = Number of persons ill Average population during a time period Example: Persons ever diagnosed with cancer = Average population ARC 2,293 = 5.5% 41,837 19 Definition of Incidence • The number of new cases of a disease that occur in a group during a certain time period. ARC 20 Example: Incidence Data • Number of new cases of HIV infection diagnosed in a population in a given year: a total of 164 HIV diagnoses were reported among American Indians or Alaska natives in the U.S. during 2009. ARC 21 Incidence Rate • Describes the rate of development of a disease in a group over a certain time period. • Contains three elements: • Numerator = the number of new cases. • Denominator = the population at risk. • Time = the period during which the cases occur. ARC 22 Population At Risk • The denominator for incidence rates • Excludes those who have already had the disease, or can’t develop it. ARC 23 Incidence Rate Calculation Number of new cases over a time period Incidence rate = Total population at risk during the same time period X multiplier (e.g., 100,000) Number of new cases = 1,085 Population at risk = 37,105 Incidence rate = 1,085 37,105 = 0.02924/8 = 0.003655 x 100,000 = 365.5 cases per 100,000 women per year Attack Rate (AR) • Alternative form of incidence rate. • Used for diseases observed in a population for a short time period. • Not a true rate because time dimension often uncertain. • Example: Salmonella gastroenteritis outbreak • Formula: AR = ARC Ill Ill + Well x 100 (during a time period) 25 Incidence Density • An incidence measure used when members of a population or study group are under observation for different lengths of time. ARC 26 Formulas for Incidence Density Incidence Number of new cases during the time period Total person-time of observation density = If period of observation is measured in years, formula becomes: Number of new cases during the time period Incidence density = Total person-years of observation ARC 27 Example: Incidence Density ARC 28 Measures of Morbidity and Mortality I PBH 506 Fundamentals of Epidemiology Allison R. Casola, PhD, MPH, CHES ARC 29 Measures of Morbidity and Mortality II PBH 506 Fundamentals of Epidemiology Allison R. Casola, PhD, MPH, CHES ARC 30 A Note on the “Multiplier” Number of new cases over a time period Incidence rate = Total population at risk during the same time period X multiplier (e.g., 100,000) Number of new cases = 1,085 Population at risk = 37,105 Incidence rate = 1,085 37,105 = 0.02924 Incidence rate in this population is 0.029 per person per 8 years Divide by 8 0.02924 * 100,000 = 2924 cases per 100,000 women per 8 years Incidence rate= 365.5 cases per 100,000 women per year Relationship Between Prevalence and Incidence • If duration of disease is short, prevalence becomes similar to incidence. • Short duration--cases recover rapidly or are fatal. • Example: common cold ARC 32 Relationship Between Prevalence and Incidence • If duration of disease is long, prevalence increases greatly relative to incidence. • Example: HIV/AIDS prevalence ARC 33 34 35 Crude Rates, Measures of Natality • Crude birth rate • Fertility rate • General • Total • Infant mortality rate • Fetal death rate ARC • • • • Neonatal mortality rate Postneonatal mortality rate Perinatal mortality rate Maternal mortality rate 36 Crude Birth Rate Used to project population changes; it is affected by the number and age composition of women of childbearing age Number of live births within a given period Crude Birth Rate = X 1,000 Population size at the population middle of that period Sample calculation: 4,130,665 babies were born in the U.S. during 2009, when the U.S. population was 307,006,550. The birth rate was 4,130,665/307,006,550 = 13.5 per 1,000. ARC 37 General Fertility Rate Used for comparisons of fertility among age, racial, and socioeconomic groups. General fertility rate # of live births within a year X 1,000 women aged 15-44 # of women = aged 15-44 yrs. during the midpoint of the year Sample calculation: During 2009, there were 61,948,144 women aged 15 to 44 in the U.S. There were 4,130,665 live births. The general fertility rate was 4,130,665/61,948,144 = 66.7 per 1,000 women aged 15 to 44. ARC 38 Total Fertility Rate • This rate is “[t]he average number of children that would be born if all women lived to the end of their childbearing years and bore children according to a given set of age-specific fertility rates.” • In the United States, the total fertility rate was 2.06 in 2012. This rate is close to • The replacement fertility rate is 2.1. ARC 39 Infant Mortality Rate Used for international comparisons; a high rate indicates unmet health needs and poor environmental conditions. ARC 40 Fetal Death Rate Used to estimate the risk of death of the fetus associated with the stages of gestation. ARC 41 Fetal Death Ratio Refers to the number of fetal deaths after gestation of 20 weeks or more divided by the number of live births during a year. Fetal Death Ratio = ARC Number of fetal deaths after 20 weeks or more gestation X 1,000 (during a year) Number of live births 42 Neonatal Mortality Rate • Reflects events happening after birth, primarily: • Congenital malformations • Prematurity (birth before gestation week 28) ARC 43 Neonatal Mortality Rate Formula ARC 44 Postneonatal Mortality Rate Measures risk of dying among older infants during a given year. ARC 45 Perinatal Mortality Rate Reflects environmental events that occur during pregnancy and after birth; it combines mortality during the prenatal and postnatal periods. ARC 46 Perinatal Mortality Ratio ARC 47 Maternal Mortality Rate Reflects health care access and socioeconomic factors; it includes maternal deaths resulting from causes associated with puerperium (period after childbirth), eclampsia, and hemorrhage. ARC 48 Measures of Morbidity and Mortality II PBH 506 Fundamentals of Epidemiology Allison R. Casola, PhD, MPH, CHES ARC 49 Adjusted Rates II PBH 506 Fundamentals of Epidemiology Allison R. Casola, PhD, MPH, CHES ARC 1 Adjusted Rates • Summary measures of the rate of morbidity or mortality in a population. • Statistical procedures have been applied to remove the effect of differences in composition of various populations. • Two Methods: Direct and Indirect Adjustment • Can adjust for any type of variable (age, gender, race/ethnicity, typically demographics) • Which variables you adjust for depends on… • information available • What demographics may be different between populations ARC 2 Direct Method • The direct method may be used if age-specific death rates in a population to be standardized are known and a suitable standard population is available. • Typically use 2000 census ARC 3 Indirect Method • Indirect method may be used if age-specific death rates of the population for standardization are unknown or unstable, for example, because the rates to be standardized are based on a small population. • The standardized mortality ratio (SMR) can be used to evaluate the results of the indirect method. ARC 4 Standardized Mortality Ratio (SMR) This is a relative rate Same formula for Standardized Incidence Ratio (SIR) ARC 5 Interpretation of SMR (and SIR) • If the observed and expected numbers are the same, the SMR would be 1.0, indicating that observed mortality is not unusual. • An SMR of 2.0 means that the death rate in the study population is two times greater than expected. ARC 6 Standardized Mortality Ratio (SMR) This is a relative rate Same formula for Standardized Incidence Ratio (SIR) ARC 7 Indirect Age Adjustment 1.Calculate this column 2. Sum the expected deaths SMR = (502/987.9) X 100 = 50.8% or .51 ARC 3. Calculate SMR 8 Indirect Age Adjustment 1.Calculate this column 2. Sum the expected deaths SMR = (502/987.9) X 100 = 50.8% or .51 ARC 3. Calculate SMR 9 Adjustment Summary • Accounting for the difference in demographic structure between populations for comparison • Direct: Superficial death rates that arise from a standard population to which the age specific death rates from two or more populations of interest are applied • Indirect: Comparison of the observed and expected death counts from a population of interest if that population of interest died at the same rate as a reference population • We’ve only discussed age differences, but these methods can be applied to any demographic variable where the difference in the distribution of that demographic variable has the potential to influence population health rates ARC 10 Descriptive Epidemiology • Characterizes who, where, and when in relation to what (the outcome of interest • Person: characteristics • Age, sex, occupation of individuals affected • Place: geography • Residence, work environment, hospital of the affected individuals • Time: when it occurred • When diagnosis, reporting, testing occurred ARC 11 Descriptive Epidemiology ARC 12 Adjusted Rates II PBH 506 Fundamentals of Epidemiology Allison R. Casola, PhD, MPH, CHES ARC 13 Adjusted Rates I (The process of standardization) PBH 506 Fundamentals of Epidemiology Allison R. Casola, PhD, MPH, CHES ARC 1 Adjusted Rates • Summary measures of the rate of morbidity or mortality in a population. • Statistical procedures have been applied to remove the effect of differences in composition of various populations. ARC 2 Age-Specific Rate (Ri) ARC 3 Method for Calculation of AgeSpecific Death Rates ARC 4 Mortality rate in six countries, 1986 Country Mortality rate (per 1000) Costa Rica 3.8 Venezuela 4.4 Mexico 4.9 Cuba 6.7 Canada 7.3 US 8.7 Are people living in Costa Rica or Venezuela at lower risk of mortality than people in Canada or the U.S.? ARC 5 Mortality rate in six countries, 1986 Country Crude Mortality rate (per 1000) Costa Rica 3.8 Venezuela 4.4 Mexico 4.9 Cuba 6.7 Canada 7.3 US 8.7 Age is a confounder of the observed association between country and mortality! Much higher proportion of older individuals in U.S., Canada After adjusting for age, Canada and U.S. have lowest rates ARC 6 Adjusted Rates • Summary measures of the rate of morbidity or mortality in a population. • Statistical procedures have been applied to remove the effect of differences in composition of various populations. • Two Methods: Direct and Indirect Adjustment • Can adjust for any type of variable (age, gender, race/ethnicity, typically demographics) • Which variables you adjust for depends on… • information available • What demographics may be different between populations ARC 7 Direct Method- Age Adjustment • The direct method is used if age-specific death rates in a population to be standardized are known and a suitable standard population is available. Adjustment = Standardization ARC 8 The “Standard” Population • Year 2000 population • Replaces the standard based on 1940 population ARC 9 Adjustment: Goals • The goal of adjustment (or standardization) is not to get strata-specific rates • Main goal is to adjust the overall population rate by calculating what the rate would be if the population demographic was similar to the standard population • Calculation of the “expected” #/rate • Main goal is to get an overall rate for comparison purposes that is not influenced by the variable on which you adjusted (like, Age) ARC 10 Direct Method for Adjustment of Rates Say you want to compare rates of mortality between 2003 and 2015… You know population demographics have changed since then, so you want to age adjust… First you age-adjust the 2003 data… 1.Calculate this column 3. Calculate the age-adjusted rate 2.Add them up Then, you do the same thing with the 2015 data Weighted Method for Direct Rate Adjustment ARC 12 In Summary: Direct Method- Age Adjustment • The direct method is used if… • age-specific death rates are known • suitable standard population is available • Result is an absolute rate. Represents the amount of death or disease in the pop if the distribution was like the standard population ARC 13 Adjusted Rates I (The process of standardization) PBH 506 Fundamentals of Epidemiology Allison R. Casola, PhD, MPH, CHES ARC 14