Week 3 Flashcards
Epidemiology
the study of determinants, distribution and frequency of disease in human population
* studies infectious diseae and chronic disease, mental health, quality of life, environmental health
What is the purpose of epidemiology?
- describe the DISTRIBUTION of disease
- identify RISK FACTORS associated with an increased probablity of disease occurrence
- PREVENTION of disease occurrence by modifying identified risk factors
Descriptive Epidemiology
- to characterize the amount and distribution of disease within a population
- identify health problems and patterns of disease that exist
Analytic Epidemiology
- testing a specific hypothesis about the relationship of a disease to a putative cause
- conducting an epidemiologic study relating exposure of interest to disease of interest
Descriptive Epidemiology
Common Person
Who is affected?
* age, gender, race, SES, occupation, behaviors
Descriptive Epidemiology
Common Place
Where are cases occurring?
* geographic location, environmental conditions, and population density
Descriptive Epidemiology
Common Time
When are cases occurring?
* seasonality, time of day, temporal trends
Survey Study
descriptive research that aims to characterize a population of interest
What are strengths of Survey Studies?
collection of in-depth information with relatively low ‘cost’ to the researcher and participant
What are the limitations of Survey Studies?
validity of self-reports and causal inference is challenged
What are two examples of Survey Studies?
- NHANES
- BRFSS
Survery Study
Behavioral Risk Factor Surveillance Survey (BRFSS)
ongoing telephone survey of risk factors in American adults
* identify emerging health problems
* establish and track health objectives
* evaluate public health policies and programs
Survey Study
The National Health and Nutrition Examinations Survey (NHANES)
combines surveys and in-person examinations
* interviews includes: demographic, SES dietary, and health-related questions
* examination consists of: medical, dental, physiological measurements
Ecological studies
compares group-level characteristics to group-level outcomes
What are the stengths and limitations of Ecological Studies?
Strength:
* cheap and easy to conduct
Limitation:
* analysis of group-level data can produce spurious results and may not be generalizable to individuals
Ecological Fallacy
occurs when incorrect conclusions about individual-levle relationships are drawn from group-level data
* logical error b/c characteristics of a group do not necessarily apply to each individual in the group
Observational Epidemiology
Cross Sectional - Purpose
to examine the prevalence of the outcome in a specific population at a single point in time
Observational Epidemiology
Cross Sectional - Study Design
observational study where data on both exposure and outcome are collected simultaneously
Observational Epidemiology
Cross Sectional - Advantages
- relatively inexpensive and quick
- can estimate prevalence of outcome of interest bc sample is usually taken from population
- many outcomes and risk factors can be assessed
- useful for public health planning
Observational Epidemiology
Cross Sectional - Disadvantages
- not effective in rare disease
- only a snapshot = issue of temporality
- evidence of causal relationships are weak
Observational Epidemiology
Cross Sectional - Measure of Association
prevalence ratio
Observational Epidemiology
Case Control - Purpose
to investigate the relationship between an exposure and an outcome by comparing individuals with the outcome to those without
Observational Epidemiology
Case Control - Study Design
retrospective, observational study where participants are selected based on their disease status, and past exposure is examined
Observational Epidemiology
Case Control - Advantages
- appropriate for the study of rare outcomes
- able to study multiple risk factors
- compared to cohort and RCTs, faster and cheaper
Observational Epidemiology
Case Control - Disadvantages
- cannot determine absolute risk
- recall bias
- can only study one disease at a time
- temporal ambiguity
- inefficient if exposure is rare
- selection of controls could be difficult
Observational Epidemiology
Case Control - Measures of Association
odd ratio (OR)
Observational Epidemiology
Cohort - Purpose
to investigate the causes of disease by following a group of exposed and unexposed individuals over time
Observational Epidemiology
Cohort - Study Design
prospective or retrospective; participants are grouped based on exposure status and followed to see if the develop the outcome
Observational Epidemiology
Cohort - Advantages
- can estimate incidence (risk) of disease
- exposure preceds development of disease
- multiple outcomes can be studied
- good for studying rare exposures
- provides complete description of exposure, including rate of progression
Observational Epidemiology
Cohort - Disadvantages
- long-term follow-up required
- expensive
- generally large sample sizes needed
- changes of time in criteria and methods
- inefficient for rare diseases
- secular trends in tech and behavior
Observational Epidemiology
Cohort - Measure of Association
- relative risk (RR)
- incidence rate ratio
Observational Epidemiology - Case Control
Odd Ratio equation
OR = (a x d) / (b x c)
Observational Epidemiology - Cohort
Relative Risk equation
RR = (a / (a+b)) / (c / (c+d))
