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DESIGN STUDY OF ENVIRONMENTAL EPIDEMIOLOGY AND OCCUPATIONAL HEALTH, Essays (university) of Epidemiology

Universitas Andalas (UA)Epidemiology

Ecological studies or correlation studies focus on the relationship between diseases and studied factors in aggregate units. Cohort studies involve observing a group of individuals over time to evaluate the effects of intervention or exposure. Double cohort studies compare two groups of individuals simultaneously. Closed cohort studies have fixed membership, and prospective cohort studies measure risk factors and follow up on disease incidence in the future. Retrospective cohort studies measure

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DESIGN STUDY OF ENVIRONMENTAL EPIDEMIOLOGY AND OCCUPATIONAL
HEALTH
INTRODUCTION
Background
Epidemiology is a branch of science that studies the distribution, patterns, and determinants
of health conditions and diseases in a particular population. Epidemiology aims to develop
effective prevention, control and health intervention strategies based on the results of risk factor
analysis. Epidemiology uses various research designs to investigate the relationship between
various exposures and health conditions in populations.
There are two types of research designs in epidemiology, namely experimental and
observational research. Observational research aims to see the relationship between many factors
or variables without intervention. Observational research consists of descriptive research and
analytical research. Observational studies include ecological studies, cross-sectional studies, case-
control studies, and cohort studies. Meanwhile, experimental research aims to investigate the
cause-and-effect relationship between variables by manipulating one variable and seeing the
changes produced in another. Experimental studies include randomized controlled trials (RCTs)
and quasi-experimental studies.
Question Formulation
Based on the background above, the formulation of the problems raised includes:
a. What is ecological studies?
b. How is a single cohort study different from a double cohort study?
c. How is a closed cohort different from an open cohort?
d. How is the difference between a prospective cohort and a retrospective cohort
e. What is nested case control?
f. What is a crossover study?
g. What is the difference between a quasi-experiment and a true experiment?
h. Mention research examples from the study design!
Purpose of Writing
The purpose of this writing is to find out the types of research designs in epidemiology, the
differences in each study, the advantages and disadvantages and research examples of each type
of research design.
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DESIGN STUDY OF ENVIRONMENTAL EPIDEMIOLOGY AND OCCUPATIONAL

HEALTH

INTRODUCTION

Background Epidemiology is a branch of science that studies the distribution, patterns, and determinants of health conditions and diseases in a particular population. Epidemiology aims to develop effective prevention, control and health intervention strategies based on the results of risk factor analysis. Epidemiology uses various research designs to investigate the relationship between various exposures and health conditions in populations. There are two types of research designs in epidemiology, namely experimental and observational research. Observational research aims to see the relationship between many factors or variables without intervention. Observational research consists of descriptive research and analytical research. Observational studies include ecological studies, cross-sectional studies, case- control studies, and cohort studies. Meanwhile, experimental research aims to investigate the cause-and-effect relationship between variables by manipulating one variable and seeing the changes produced in another. Experimental studies include randomized controlled trials (RCTs) and quasi-experimental studies. Question Formulation Based on the background above, the formulation of the problems raised includes: a. What is ecological studies? b. How is a single cohort study different from a double cohort study? c. How is a closed cohort different from an open cohort? d. How is the difference between a prospective cohort and a retrospective cohort e. What is nested case control? f. What is a crossover study? g. What is the difference between a quasi-experiment and a true experiment? h. Mention research examples from the study design! Purpose of Writing The purpose of this writing is to find out the types of research designs in epidemiology, the differences in each study, the advantages and disadvantages and research examples of each type of research design.

DISCUSSION

A. Ecological Studies Ecological studies or correlation studies are epidemiological studies that aim to describe the correlative relationship between diseases and the factors studied in aggregate (group) units of analysis. (1) The design of ecological studies can be classified into two, namely: a. Whether primary cohorts are measured (exploratory vs analytical studies) b. (^) Whether subjects were grouped by place (multi-group study), by time (time trend study), or by place and time (mixed study). (2) Excess Deficiency Can use existing data (secondary data) Unable to analyze causality relationships at the individual level Appropriate for use in the first investigation of the relationship of exposure to factors and disease Unable to control the influence of confounding factors May investigate the effects of exposure that are impossible to quantify at an individual level, such as air pollution Measurement errors due to exposure data collected in the form of group data May generate hypotheses for further investigation Exposure and outcomes are not measured in the same individual Easy, fast and inexpensive to do because it uses existing data Lack of adequate and available data in aggregate form(3) Research Example: Research Title: Ecological Study of the Prevalence of Diabetes Mellitus with Stroke in Indonesia(4) Method: This study uses secondary data from the 2018 Basic Health Research Results with a research population of โ‰ฅ 15 years old population according to provinces in Indonesia as many as 713,783 people. B. Single Cohort Study vs Double Cohort Study A single cohort study involves observing one group of individuals over a period of time to assess the effects of an intervention or exposure to a particular outcome.

death or non-actionability, but no added subjects are added. As a result, the closed cohort always decreases over time. (8) An open cohort study is a cohort study with groups being open or dynamic, which means that members can leave or be added during the research period. (8) Excess Deficiency Closed Cohort Efficient and cost-effective because data collection is only one population Loss follow-ups that reduce cohort representation and arise bias. Investigate the natural history of disease or health outcomes Difficulty controlling the role factors associated with exposure Investigate various outcomes associated with a single exposure May not be suitable for investigating rare outcomes The prospective nature of this study reduces the potential for memory bias or misclassification of exposure status. Not suitable for investigating changes in exposure status over time Open Cohort Allows changes in the investigation of exposure status over time Loss follow-up that can reduce cohort representation and arise bias. Can investigate the natural history of the disease Difficulty controlling factors related to exposure and outcomes can be used to investigate various outcomes associated with a single exposure or risk factor. The design can be more complex, especially if new individuals are added to the cohort at some point in time. This design can be used to investigate rare outcomes or exposures. Not suitable for investigating the effects of exposure on specific populations because new individuals with distinctive characteristics can be added Research Example:

1. Closed Cohort Studies

Title: Risk Factors for Conversion of Hip Arthroscopy to Total Hip Arthroplasty: A Large Closed- Cohort Study (9) Method: This study is a series of consecutive cases of hip arthroscopy procedures from September 2008 to November 2018 in the electronic medical records of Kaiser Permanente Northern California. Patients are admitted with a follow-up of at least 2 years or if they are converting to THA within 2 years (primary outcomes) regardless of the time of follow-up.

2. Open Cohort Studies Title: A one-year hospital-based prospective COVID- 19 open-cohort in the Eastern Mediterranean region: The Khorshid COVID Cohort (KCC) study (10) Method: A hospital-based prospective surveillance study with the subject of the study being patients treated for COVID-19 from February 2020 - September 2020 at Khorshid Hospital in Isfahan. This cohort has two phases. The first phase is the admission information of the inpatient until the patient is discharged or dies. In contrast, the second phase is related to patients discharged from the hospital due to future symptoms or social factors. Six hundred patients were enrolled in the first phase, while four hundred and ninety patients with full information were analyzed in the study. D. Prospective Cohort vs Retrospective Cohort Prospective cohort/concurrent cohort/longitudinal is a study design in which risk factors are measured at the beginning of the study, then followed up to see the incidence of disease in the future. Thus, at the beginning of the study there were no subjects who had outcomes or diseases. (11) (^) At the beginning and during the follow-up period, the researcher also collects information about other variables that are important to the study (such as role variables). (12) Retrospective/non-concurrent cohort/historical cohort is a study design in which risk factors and effects or diseases have occurred in the past before the start of the study. The variables are measured through historical records. Observation begins when the aftermath (effect) has occurred. (11) (^) Retrospective cohort research can only be conducted if risk factor data are well recorded since exposure to the population. Excess Deficiency Prospective Cohort

Excess Deficiency More efficient because exposure data collection is only on a subset of subjects Memory bias or misclassification on retrospective determination of exposure Case matching and controls will reduce potential roles Selection bias if cases and controls do not represent larger cohort studies. It can be used to investigate rare outcomes and long latent periods. The availability of exposure data may be limited, as it depends on the original cohort study data. Can investigate various exposures and their interaction with the desired results. Limitations in investigating the effects of potential role variables (15) Research Example: Title: A nested case-control study on radiation dose-response for cardiac events in breast cancer patients in Germany (16) Method: In a cohort of 11,982 BC patients diagnosed in 1998-2008, we found 494 women treated with 3D- who after experienced a cardiac event. In a nested case-control approach , these cases are matched with 988 controls. The control is a patient with no cardiac event after RT until the date of the corresponding case index. F. Crossover Study A crossover design is an iterative measurement so that each experimental unit receives a different treatment over time. This design is considered when planning clinical trials because it can result in more efficient treatment comparisons than parallel designs. (17) This design only works for conditions of a chronic nature, such as incurable asthma and its treatment only aims to improve the quality of life. (17)^ Crossover design is the design of choice for bioequivalence trials. (18) Excess Deficiency Each participant serves as their own control thus minimizing the effects of individual differences. Crossover studies may not be appropriate for treatment with long-term effects

Crossover studies can be more efficient than parallel group studies, as they require fewer participants The sequence of participants in receiving the intervention can affect outcomes and potential sequential effects. It can be used to investigate the effects of treatment on outcomes that have high variability between individuals. It needs a longer study duration to accommodate multiple interventions so there may be participants out Research Example: Title: Asthma mortality attributable to ambient temperatures: A case-crossover study in China (19) Method: Researchers used data from the National Mortality Surveillance System in China, to conduct a time-based crossover study of 15,888 people who lived in Hubei and Jiangsu provinces, China and died of asthma as the leading cause in 2015-2019. G. Quasi Experiment then True Experiment A quasi-experiment is one experiment in which the placement of the smallest unit of the experiment into the experimental and control group is not performed by random assignment. (20) Pure Experiment is an experiment in which the experimental subjects in the control and experimental groups must be randomly selected, so that there is no bias in the selection of participants. This type of study has strong control over known disruptor variables. (21) Excess Deficiency Almost Experiment Practical and feasible, especially in nursing. This provides weaker evidence of the intervention's effects. The resources required for experimentation are also reduced. The presence of unforeseen factors that can affect the yield. Pure Experiments Can know the cause-and-effect relationship between variables. Some cases are unable to present the actual occurrence Random selection of research subjects to minimize the effects of role variables In some cases, it may be unethical to manipulate independent variables for research purposes.

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