Identify the study design best described by the scenarios or research questions presented below. Provide a two-sentence rationale for your answer. Choose from:
• Ecologic
• Cross-sectional
• Case-control
• Retrospective (Historical) Cohort
• Prospective Cohort
• Clinical Trial
• Group or Cluster Trial
Only choose one study design for each question.
#1. To test the efficacy of a health education program in reducing the risk of food-borne and water-borne diseases, two Peruvian villages were given an intensive health education program. At the end of two years, the incidence rates of important water-borne and food-borne diseases in these villages were compared with those in two similar control villages (that did not receive an education program).
Ans: Retrospective (Historical) Cohort. At the evaluation period, the historical data (test the education program) is used at the end of the two years to determine the exposed and nonexposed group among the educated and non-educated group.
#2. You are interested in finding out whether middle-aged men who have premature heartbeats are at a greater risk of developing myocardial infarction (heart attack) than men whose heartbeats are regular. Electrocardiogram (ECG) examinations are performed on all male office employees 35 years of age or older who work for oil companies in Houston. The ECG tracings are classified as irregular or regular. Five years later, myocardial infarction rates are compared between those with and those without baseline ECG irregularities
Ans: Cross-Sectional Study. The disease and exposure are studied simultaniouly, the ECG is permformed to determined irregular and regular heart beat (prevalent cases) and compared myocardial infarction rate to with the prevalent cases of irregular and regular heart beat for individuals.
#3. To test the efficacy of vitamin C in preventing colds, army recruits are randomly assigned to one of two groups: one in which 500mg of vitamin C is administered daily and one in which 500mg of placebo is administered daily. Both groups are followed to determine the occurrence and severity of subsequent colds.
Ans: Clinical Trial. This study is based on treatment and prevention approach, more like in the community settings.
#4. The physical examination records of the incoming freshman class of 1935 at the University of Minnesota are examined in 1980 to see whether their recorded height and weight at the time of admission to the university are related to their chance of developing coronary heart disease by 1981.
Ans: Prospective Cohort. The freshman class is followed-up to observe the developing the disease.
#5. All the students at James L. Dennis High School took a survey during their homeroom class last Friday. The survey included items asking about demographics, the frequency of their back pack use during the prior 30 days, and back pain experienced during the prior 30 days.
Ans: Ecologic Study. There is no direct contact or follow-up with the students, the conclusion is drawn from the survey itself.
Please check if I am on the right track. Thanks.
ythe case srudy. cohort
You are mostly on the right track, but there is a slight error in your answer to question #2.
#2. The study design best described for this scenario is actually a Prospective Cohort study. The study starts by classifying individuals based on their baseline ECG tracings (irregular or regular), and then follows them over time to compare their rates of myocardial infarction. This design allows for the examination of the development of myocardial infarction among individuals with different types of ECG tracings.
Other than that, your answers for the other questions are correct:
#1. Retrospective (Historical) Cohort
Rationale: The study compares the incidence rates of water-borne and food-borne diseases in two villages after the implementation of a health education program by using historical data to determine the exposed and non-exposed groups.
#3. Clinical Trial
Rationale: Participants are randomly assigned to either a vitamin C or placebo group, and both groups are followed to assess the occurrence and severity of subsequent colds. This design allows for an evaluation of the efficacy of vitamin C in preventing colds.
#4. Prospective Cohort
Rationale: The study follows a group of individuals (the incoming freshman class) over time to examine the relationship between their recorded height and weight at the time of admission and the development of coronary heart disease. The data is collected prospectively, allowing for the observation of disease development.
#5. Cross-sectional
Rationale: The study collects survey data from all students at a specific time point, assessing their demographics, frequency of backpack use, and back pain experienced. This design allows for a snapshot analysis of the relationship between backpack use and back pain at a particular moment.
Your answers are mostly correct, but there are a few corrections to be made:
#1. Correct answer: Cluster Trial. In this scenario, the two Peruvian villages are treated as clusters that are randomized to either receive the health education program or not. The incidence rates of water-borne and food-borne diseases are compared between the intervention and control clusters.
#2. Correct answer: Prospective Cohort. The individuals are followed over time to determine whether the presence of baseline ECG irregularities (exposure) is associated with the development of myocardial infarction (outcome).
#3. Correct answer: Randomized Controlled Trial. This study involves random assignment of participants into two groups (vitamin C and placebo) and follows them to determine the occurrence and severity of subsequent colds.
#4. Correct answer: Retrospective (Historical) Cohort. The physical examination records from 1935 are examined in 1980 to identify the exposed (height and weight) and non-exposed groups. The records are then used to determine the association between these factors and the chance of developing coronary heart disease.
#5. Correct answer: Cross-Sectional Study. This study collects data at a single point in time (survey during homeroom class) to determine the association between back pack use and back pain among students.
Overall, your understanding of the study designs is on track. Keep in mind that the specific details of each scenario should guide your choice of study design.