Homework 4

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School

California State University, Long Beach *

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Course

101

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Industrial Engineering

Date

Dec 6, 2023

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pdf

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Uploaded by DoctorFangPenguin11

FMPH 101 Homework 4 Winter 2023 Name: Valerie Chavez Homework #4: Cohort Studies Assignment due by Thursday 02/16/23 via Gradescope. For calculations show all work involved. Submit answers within this document and do not submit reformatted assignments with just the answers. Please select corresponding pages for answers in Gradescope when submitting assignment. Question 1 Please indicate within in the table below whether the statements are true or false. Answers: A. Incidence rates cannot be estimated from a retrospective cohort study False B. Prospective cohort studies are good for studying rare exposures True C. Multiple diseases can be studied in a cohort study. True D. Temporality can only be established in prospective cohort study True Question 2 Researchers conducted a prospective cohort study to investigate whether the use of oral contraceptives increases a woman’s risk of stroke. 3500 women between the ages of 18 and 35 with no history of stroke were asked about their oral contraceptive (OC) use in January 2016. 1607 women reported current OC use and 1893 did not. At the end of the 3-year follow-up period, 249 of the OC users and 201 of the OC non-users had suffered from a stroke. Stroke No Stroke Total OC use 249 1607 1358 No OC use 1692 1893 201 Total 450 3050 3500 A. Based on the information provided above, please fill-in the 2x2 table above. B. What was the cumulative incidence of stroke over the 3-year period for the entire cohort? Show all of your work and round your final answer to 2 decimal points. Cumulative incidence of stroke for entire cohort: (249+201) / 3500-> 450 / 3500= 0.13 or 13% C. What was the cumulative incidence (risk) of stroke over the 3-year period among OC users? Show all of your work and round your final answer to 2 decimal points. Cumulative incidence of stroke for OC users: 249 / 1607= 0.15 or 15%

FMPH 101 Homework 4 Winter 2023 D. What was the cumulative incidence (risk) of stroke over the 3-year period among OC non- users? Show all of your work and round your final answer to 2 decimal points. Cumulative incidence of stroke for OC non-users: 201 / 1893= 0.11 or 11% E. Calculate the risk ratio (relative risk) for stroke comparing OC users to OC non-users. Show all your work and round your final answer to 2 decimal points. Risk ration for stroke comparing OC users to OC non-users: 0.15 / 0.11= 1.36 F. Interpret the risk ratio (relative risk) calculated in (e) above. The risk ratio (relative risk) is 1.36 which means that women who use OC are 1.36 times more likely to experience a stroke compared to women who do not use OC. G. Based on the risk ratio (relative risk) you calculated in (e) above, is OC use potentially harmful or potentially protective? Please explain your answer. Based on the risk ratio (relative risk) OC use is potentially harm because we see from the data that those who take OC are 1.36 times more likely to get a stroke. H. Suppose some women were lost to follow-up during the 3-year study period. Calculate the incidence rate for stroke among OC users and OC non-users assuming OC users were observed and at risk for 21,311 person-months and OC non-users were observed and at risk for 30,251 person-months. Show all your work for each calculation. Express your final answers per 1,000 person-months and round your final answers to 1 decimal points. Incidence rate of stroke for OC users: 249 / 21311= 0.117 or 1.2 per 1000 person-months Incidence rate of stroke for OC non-users: 201 / 30251= 0.0066 or 0.7 per 1000 person-months I. Calculate the rate ratio for stroke comparing OC users to OC non-users. Show all your work and round your final answer to 2 decimal points. Rate ration for stroke comparing OC users to OC non-users: 0.117 / 0.0066= 17.73 or 1.2 / 0.7= 1.7 per 1000 person-months J. Interpret the rate ratio calculated in (i) above. The rate ratio of 1.7 per 1000 person-months means that women who use OC are 1.7 times more likely to experience a stroke compared to women who do not use OC. Question 3 BACKGROUND It has been suggested that vaccination against measles, mumps, and rubella (MMR) is a cause of autism. METHODS In 2005, we conducted a cohort study of all children born in Denmark from January 1991 through December 1998. The cohort was selected on the basis of data from the Danish Civil Registration System, which assigns a unique identification number to every live-born infant and new resident in Denmark. MMR-vaccination status was obtained from the Danish National Board of Health. Information on these same children's autism status was obtained from the Danish Psychiatric Central Register, which contains information on all diagnoses received by patients in psychiatric hospitals and outpatient clinics in Denmark. We obtained information on potential confounders from the Danish Medical Birth Registry, the National Hospital Registry,

FMPH 101 Homework 4 Winter 2023 and Statistics Denmark. RESULTS Of the 537,303 children in the cohort (representing 2,129,864 person-years), 440,655 (82.0 percent) had received the MMR vaccine. We identified 316 children with a diagnosis of autistic disorder and 422 with a diagnosis of other autistic-spectrum disorders. After adjustment for potential confounders, the relative risk of autistic disorder in the group of vaccinated children, as compared with the unvaccinated group, was 0.92, and the relative risk of another autistic- spectrum disorder was 0.83. A. What kind of cohort study is this, prospective or retrospective? This is a retrospective cohort study B. What are two benefits of this type of cohort study versus the other? (Would give full credit if answers make sense. They don’t need to be specifically these two.) Two benefits of this type of cohort study is that it has the ability to study rate outcomes and exposures, and that it also has the ability to establish temporal relationships between exposures and outcomes. C. Were children already classified as developing the outcome (Autism) prior to investigators starting this study? The children were not classified as developing the outcome (Autism) prior to the start of this study. The investigators got the information on autism status from the Danish Psychiatric Central Register after the study was begun. D. Were children already exposed (vaccinated) prior to investigators starting this study? Yes they were already vaccinated prior to investigators starting the study as they were able to obtain information on MMR vaccination status from the Danish National Board of Health for children who were vaccinated before the study had started. E. Do the study results provide evidence that vaccination was a risk factor for autism? The study does not provide evidence that vaccination was a risk factor for autism. The risks for autism was below for the vaccinated group meaning a lower risk compared to those unvaccinated. Question 4 The table shows whether a person survived a snakebite or not depending on whether they were administered antivenom. Death from a snakebite Survived a snakebite Total No Antivenom ( exposed ) 185 221 406 Antivenom administered ( unexposed ) 92 365 457 A. Calculate the incidence of death attributable to not having antivenom (attributable risk). Round answer to three decimal places. Formula: (Incidence in those without antivenom) – (incidence in those with antivenom) 185 / 406 x 100= 45.567% 92 / 457 x 100= 20.131% Incidence of attributable to not having antivenom= 45.567 - 20.131= 25.436%

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FMPH 101 Homework 4 Winter 2023 Incidence of death attributable to not having antivenom= .254 B. In every 1000 snake bites, how many deaths are prevented by administering Antivenom? As 25.436% of deaths that happen are due to not having antivenom, then in every 1000 snake bites the number of deaths prevented is: 1000 x 0.25436= 254.36= 254 C. Calculate the percent of incidence of death attributable to not having antivenom (attributable risk percent) Attributable risk= (185/406)-(92/457) / (185/406) x100= 0.456-0.201 / 0.456-> 0.255 / 0.456= 0.559 x 100= 55.9% D. Explain what the answer calculated for 4C means. (2 sentences or less) The attributable risk is the rate of a health outcome in exposed individuals which can be caused by exposure. The incidence of deaths attributable to not having the antivenom from the snake bite is 55.9%. Question 5 The table below presents hypothetical data on the mortality due to pancreatic cancer among individuals classified as excessive alcohol consumers and individuals classified as non-alcohol consumers, as well as the total population. Deaths per 100,000 standard population Excessive alcohol consumers Non-excessive or no alcohol consumers Total Population Pancreatic cancer deaths 4.93 1.44 2.90 A. How much of pancreatic cancer mortality among those who consume excessive alcohol is due to their alcohol abuse? Show your work (including formula used), round your answer to 2 decimal places, and express your answer per 1,000 person-years. Attributable fraction= (rate of disease among exposed – rate of disease among unexposed)/ rate of disease among exposed population AF= (4.93 – 1.44) / 4.93 = 0.71% per person-years B. How much of all cancer deaths in the total population is due to excessive alcohol consumption? Show your work (including formula used), round your answer to 2 decimal places, and express your answer per 1,000 person-years. Attributable fraction x total number of pancreatic cancer deaths in total population Proportions of deaths due to excessive alcohol consumption= 0.71 x 2.90= 2.05 C. If excess alcohol consumption were eliminated, what proportion of the incidence pancreatic cancer in the total population would be prevented? Show your work (including formula used) and round your answer to 1 decimal place. 71% of pancreatic cancer cases in the excessive alcohol consumers can be attributed to their excessive consumption, because we could not calculate the complete incidence due to not having the total number of person-years. This means we cannot calculate this proportion.

Homework 4

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