Epidemiology Flashcards
(22 cards)
What is epidemiology?
The study of the distribution of disease/s within a population and the factors that determine the development of these diseases
What is the difference between frequency and rates of disease?
Frequency - the total number of events
Rates - total number of events in relation to the population
What are the 3 aims of epidemiology?
- To describe the patterns, distributions and extent of the disease within populations
- To understand determinants and why they occur in populations
- Provide information necessary to manage, plan, prevent, control and treat the disease
What are some examples of observational studies?
- Case-Control studies
- Cohort studies
- Cross-sectional studies
What is an example of an experimental study?
Randomised control trials (RCTs)
What is the difference between incidence and prevalence?
Incidence - the total number of cases reported within a specified time period
Prevalence - the total number of cases existing at any particular point in time
In what order of heirachy will the following studies be? (starting from most appraised)
- Retrospective cohort studies
- RCT
- Cross-sectional studies
- Prospective cohrot studies
- Ecological studies
- Case-control studies
- RCT
- Prospective cohort studies
- Retrospective cohort studies
- Case-control studies
- Cross-sectional studies
- Ecological studies
(may be descriptive or analytical)
*Study infographic*
What are the distictions of a case-control study?
- Retrospective study
- Examines association between exposure and outcome/disease
- Uses a group that already has an outcome/disease vs a group that does not have the outcome/disease
- Odds Ratio (OR): a measure of the odds of developing the outcome/disease with exposure vs the odds of developing the disease/outcome without exposure
What are the distictions of a cohort study?
- Can be prospective or retrospective (usually prospective)
- Comparison of two groups with unknown (prospective) or known (retrospective) outcome/disease based on a supposed exposure
- Relative Risk (RR): The probability of the disease occuring in an exposed group vs a non-exposed group
What are the distictions of a cross-sectional study?
- Analyses data from the present point in time
- Only a snapshot
- Measures disease prevalence within a population
- Studies association of variables
What are the distictions of an ecological study?
Assesses overall rates of disease within multiple populations
- Used to make large scale comparisons
- Used to understand the relationship between outcome and exposure on population levels
What are the advantages and limitations of a case-control study?
ADV:
- Ideal for rare outcomes/diseases that do not have clear aetiology or multiple risk factors/exposures
- No follow-up required so less time consuming than cohort studies
- Suitable for diseases with long latent period (e.g. cancer)
DIS:
- Not ideal for rare exposures
- Prone to recall bias, interviewer bias
- May be difficult to select ideal participants for the control group
What are the advantages and limitations of a cohort study?
ADV:
- Ability to study many multiple outcomes as a result of a single exposure
- Can determine RR
- Clarity of the temporal sequence (did the exposure precede the outcome?)
DIS:
- Recall bias (retrospective study)
- Not ideal for rare diseases or diseases with long latency (e.g. cancer)
- Very expensive and time consuming
- Requires follow-up, potential loss of participants
What are the advantages and limitations of a cross-sectional study?
ADV:
- Quick and inexpensive
- Follow-up not required
- Can show associations between variables
DIS:
- Does not show temporality between outcomes/disease and exposures
- Unable to infer cause-effect relationship
- May be compromised by frequent changes in disease incidence (e.g. infectious disease)
What are the advantages and limitations of an ecological study?
ADV:
- Relatively quick and inexpensive
- Uses existing data
- Ideal for studying large populations
DIS:
- Ecological bias
- Information may not be representative at individual level
- Unable to infer cause-effect relationship
What is the purpose of an observational study (cohort, case-control, cross-sectional)?
To study participants without any intervention. To investigate the ‘natural’ state of risk factors, disease and outcomes.
What is the purpose of experimental studies (RCTs)?
To investigate whether people deliberately exposed to an agent/protected from an agent (such as drugs, supplements or information) have a different incidence in disease compared to the general population (by clinical trials, community trials)
What is the equation to calculate RR? How would you interpret this?
Incidence risk among exposed group / Incidence risk among non-exposed group = RR
RR = 1 = no difference
RR = >1 exposure is dangerous
RR = <1 exposure is protective
What is the equation to calculate OR? How would you interpret this?
Odds that a case was exposed / Odds that a control was exposed = OR
OR = 1 = no difference in odds
OR = >1 exposure is dangerous (odds of exposure in case-patients is greater than odds of exposure in control-patients)
OR = <1 exposure is protective (odds of exposure in case-patients is lower than odds of exposure in control-patients)
What is the equation to calculate HR? How would you interpret this?
Hazard Ratio = hazard in exposed group / hazard in unexposed group
HR tells yopu whether or not the intervention/treatment has shortened the duration of the disease
*used in clinical trials (experimental study designs, RCTs)
What are the 5 steps of EBP?
ASK- Formulate an answerable clinical question
ACCESS - Search for the best evidence
APPRAISE - Appraise the evidence for its validity and usefulness in answering the question
APPLY - Intergrate the evidence into your clinical results/decision
ASSESS - Evaluate the effectiveness of the process
