Lecture 9C: Epidemiology Flashcards
What is epidemiology?
Study of distribution and determinants of disease, injury, or dysfunction in human populations.
Define prevalence.
A proportion reflecting the number of existing cases of a disorder relative to the total population at a given point in time.
For cross-sectional designs
What is point prevalence?
Prevalence at a single point in time.
What factors influence prevalence?
- The number of individuals who develop the condition
- The duration of illness
- The severity of illness
Define incidence.
The number of new cases of a condition in the population during a specified time period.
the risk of developing the condition during a specified time period
What is cumulative incidence (CI)?
the number of new cases divided by the number of people in the population at risk. (over a period of time)
Assumes that all subjects are followed for the entire observation period
What study design is used to measure incidence?
Prospective cohort study.
1. Select the subjects without the condition.
2. Classify the subjects according to their exposure status.
3. Follow them for a period of time and see who develops the disease
What is the objective of analytical epidemiology?
Identifying the risk factors of a particular health outcome.
What is relative risk (RR)?
Measures the likelihood that someone who has been exposed to a risk factor will develop the condition, compared with those who have not been exposed.
How is RR measured?
What do different values of RR represent?
RR=1; Exposure presents no excess risk for the outcome.
RR>1; Exposure increases risk
RR<1; Exposure decreases risk
What is an odds ratio (OR)?
A measure used in case-control studies to estimate relative risk.
How is the odds ratio calculated?
OR = (a/b) × (d/c)
What do different values of OR represent?
OR=1; No difference
OR>1; Increased risk
OR<1; Decreased risk
What is a case-control study?
A study design that compares subjects with a disease (cases) to those without (controls) to identify risk factors.
What are the advantages of prospective cohort studies?
- Determine risk of developing a disease
- Can determine incidence of disease
- Standardized data collection
- Useful if exposure is rare
What are the disadvantages of prospective cohort studies?
- Time consuming.
- Very expensive.
- Attrition.
- Large sample size needed.
- Difficult to study rare disease.
What are the advantages of case-control studies?
- better for studying rare diseases
- Quick and efficient.
- Relatively inexpensive.
- Good for further hypothesis generation.
What are the disadvantages of case-control studies?
- Selections of cases and control
(misclassification may occur). - Incomplete medical records.
- Risk factors information in the past (poor memory, recall bias, etc.).
- More susceptible to researcher bias
Prospective cohort studies v.s. Case-control studies
PCS: Classify subjects based on exposure status
CCS: Classify subjects based on disease status
Fill in the blank: The study design used to measure prevalence is __________.
Cross-sectional
Fill in the blank: The formula for cumulative incidence is __________.
of new cases over a period of time / # of people in the population at risk
True or False: A higher incidence indicates a higher prevalence.
True
What is the objective of estimating the incidence of low back pain in bus drivers?
To determine the number of new cases over a specified time period.
Match the statistic to the study design
