MindMap Gallery Epidemiological Study Designs
This infographic offers an in-depth analysis of epidemiological study designs, essential for public health research. It categorizes and describes various methodologies including experimental, cohort, case-control, and cross-sectional studies. It further delves into each type's specific approaches, such as selection of cases, control matching, and the calculation of statistical measures like risk and odds ratios. This visual guide is ideal for students, researchers, and public health professionals seeking to understand or conduct epidemiological research.
Edited at 2023-11-25 20:11:51This infographic offers an in-depth analysis of epidemiological study designs, essential for public health research. It categorizes and describes various methodologies including experimental, cohort, case-control, and cross-sectional studies. It further delves into each type's specific approaches, such as selection of cases, control matching, and the calculation of statistical measures like risk and odds ratios. This visual guide is ideal for students, researchers, and public health professionals seeking to understand or conduct epidemiological research.
The chain of infection is a crucial concept in understanding and preventing the spread of infectious diseases. It outlines the sequential events necessary for an infection to be transmitted from a source to a susceptible host. In this mind map, we will explore the components of the chain of infection, including the infectious agent, reservoir, portal of exit, mode of transmission, portal of entry, and susceptible host. By visualizing this interconnected chain, we can better comprehend how infections propagate and identify key points for intervention and control.
The role of chemical mediators in inflammation is a complex and essential aspect of the body's immune response. This mind map will delve into the various chemical mediators involved in the inflammatory process, including cytokines, prostaglandins, leukotrienes, and histamine. By visually mapping out the interactions and functions of these chemical mediators, this mind map aims to provide a comprehensive overview of how they contribute to the initiation, propagation, and resolution of inflammation.
This infographic offers an in-depth analysis of epidemiological study designs, essential for public health research. It categorizes and describes various methodologies including experimental, cohort, case-control, and cross-sectional studies. It further delves into each type's specific approaches, such as selection of cases, control matching, and the calculation of statistical measures like risk and odds ratios. This visual guide is ideal for students, researchers, and public health professionals seeking to understand or conduct epidemiological research.
The chain of infection is a crucial concept in understanding and preventing the spread of infectious diseases. It outlines the sequential events necessary for an infection to be transmitted from a source to a susceptible host. In this mind map, we will explore the components of the chain of infection, including the infectious agent, reservoir, portal of exit, mode of transmission, portal of entry, and susceptible host. By visualizing this interconnected chain, we can better comprehend how infections propagate and identify key points for intervention and control.
The role of chemical mediators in inflammation is a complex and essential aspect of the body's immune response. This mind map will delve into the various chemical mediators involved in the inflammatory process, including cytokines, prostaglandins, leukotrienes, and histamine. By visually mapping out the interactions and functions of these chemical mediators, this mind map aims to provide a comprehensive overview of how they contribute to the initiation, propagation, and resolution of inflammation.
Studies
Experimental studies
preventive or therapeutic measures to the test
assign exposure variable to subjects and withholding the exposure from other subjects
Types
1. Field trials
efficacy of preventive interventions applied to individuals (e.g., a vaccine trial).
2. Community trials
address the efficacy of preventive interventions applied at the group level (e.g., a health education campaign)
3. Clinical trials
address the efficacy of therapeutic interventions in ill individuals (ex: a chemotherapy trial in the treatment of cancer
Advantages
Randomize .
Control confounding
Ensure temporality
provides the strongest evidence in support of cause-effect relationships.
Randomized controlled trial (RCT)
the treatment is assigned to study subjects by mechanism based on chance
aim to
) improve existing treatments
) replace them with new and better ones.
extraneous factors o randomly distribute among the groups
Randomized controlled trial (polio trial-1954)
Concepts
referent rate provided by the control group to determine the rate in the treatment group reflected the effect of the treatment
efficacy and safety can only be fully assessed after longterm use on patients
Placebo : pharmacologically inert substance, such as a sugar pill or saline injection.
The Hawthorne effect refers to the tendency of subjects to alter their behavior in a way that is favorable to the results of the study
Blinding (masking) the study participants and investigators about the treatment being received offers just such protection
parallel design in which the experience of the treatment group and control group are compared concurrently
Data analysis Measures of effect
comparisons of incidence rates and proportions
The relative effect → rate or risk ratio: RR = R1/R0,
absolute effect of exposure → the rate or risk difference: RD = R1 − R0
For treatments → Efficacy = 1 – RR
R1 : the incidence rate or incidence proportion (risk) in the treatment group, - R0 : the incidence rate or incidence proportion (risk) in the control group.
Observational studies
Descriptive
Generation of hypotheses
Describing
Existing indicators
variabels in reality
Types
A) Case series.
Based on records of series of cases of a disease.
specific cases
b) Case report
typically describes a single patient
retrospective
C-Community need assessment or diagnosis
base-line data, identify existing community problems
d) Epidemiological description of disease occurrence.
data on occurrence and distribution of disease in population by PPT
E) Descriptive cross-sectional (community surveys)
section of the population being a sample or the whole population
provide prevalence rate at a poin
KAP studies.
f) Ecological studies.
unit of observation and description is family, school, tribe, village, town, city, district.
Analytical
Test etiological hypotheses
association between exposure to a risk factor and occurrence of a diseases.
Basic approach
Developing testable hypothesis.
Control for extraneous variable that can confound the result
Types
Cross-sectional studies
The investigator measures exposure and disease simultaneously in a representative sample of the population
Assess the prevalence of outcomes and exposures
Determine associations but not causation
Very well suited for describing variables and their distribution patterns
If the sample is drawn from the diseased population → this would be a case series study that describes the disease in this section.
Period prevalence provides the better measure of the factor because it includes all cases between two dates
Case-control studies
retrospective
Rare diz
Retroactively compare exposures between cases and controls
potentional of bias
Indviduals may not be able to recall all exposures accurately → Recall bias
If the cases and controls are not selected similarly → lead to selection bias.
Odds ratio=
We are not able to estimate the incidence or prevalence
Selection of cases
define the cases as specifically as possible.
• Inclusion-exclusion criteria should clearly be specified.
cases are matched with controls or vise versa → cases and controls come from the same populatio
Matching
Matching is a useful technique to increase the efficiency of study
eliminate confounding effect of variables
achieve comparability of cases –controls,
ensure that sufficient numbers will be available in categories of interest.
Advantages
requiring smaller sample
No follow-up.
faster and are inexpensive
study multiple exposures in the same outcome unless rare ones.
association of risk factors and outcomes in outbreaks
We can use logistic regression models for multivariate analysis in case-control - matched case-control studies
Case–control studies start by selecting diseased and non-diseased.
Cohort studies
follow the experiences of individuals in closed populations.
the population is disease free
Exposed and non exposed
Cohort start with disease free and ‘‘wait’’ for develop the outcome
Types
A) Prospective
planned to observe events had yet to occur
Cases are ascertained based on criteria referred to as the case definition.
community - Diagnosed or treated patients
Measurements:
1. Incidence
often per 1000
New cases divided by population at risk
2. Relative risk (effect RR)
RR = incidence in (exposed) / incidence in (unexposed)
3. Attributable risk (AR).
The difference ( - ) between the incidence in exposed and unexposed.
Advantages/Disadvantages
determine cause-effect relationship.
Less bias
- Can be generalized
Long-
expensive
Not fit for rare diseases
Withdraw
B) retrospective cohort studies
carried out using records of events that had occurred in the past.
Disadvantages
Relevant variables may not be available, or incomplete, etc
Not sure if subjects were free form diseases at start of comparison
C) ambidirectional cohort studies
→Cohort studies that combine prospective data with retrospective data.
Determine exposure-disease relationship
Examples about cohort studies
Hippocrates (400 BCE) ; the seed of the observational cohort design
1935 ; the first recorded use of the term cohort made its appearance in epidemiology
middle of the 20th century, the epidemiologic transition
modern cohort studies initially addressed cigarette-related diseases, cancers, and heart disease
Framingham cohort about the causes of heart disease and stroke between 1948 and 1950