Intro to Epidemiology Flashcards
Definition of epidemiology
Study of the distribution and determinants of health events and health related risk factors in specified populations
This knowledge is used to plan and evaluate strategies to prevent/manage disease in specified populations
Definition of epidemiologist
Public health scientist who analyses patterns, causes, effects of health and disease in populations
Definition of ecological epidemiology
Ecology of disease
Interaction between hosts and pathogens
Includes population and community level studies
Definition of molecular epidemiology
Contribution of genetic and environmental risk factors at the molecular level
Definition of descriptive epidemiology
Examination of frequency/geography of disease over time
Definition of etiological epidemiology
Study the causes of a disease
Definition of evaluative epidemiology
Study effects of preventative measures on outcomes
Definition of health service epidemiology
Study effects of outcomes and effectiveness of health services
Definition of clinical epidemiology
Study of the natural course of a disease and the effects of diagnostics and procedures
Definition of target populations
Total group of individuals from which the sample is drawn
Conclusions from study made on this population
Definition of the study population
Group of individuals in a study
Definition of sample population
Subjects that provide data
Definition of prevalence
No of existing and new cases of a disease in a time frame
Definition of incidence
No of new cases of a disease in a time frame
What is epidemiology
Study of the distribution and determinants of health events and risk factors in specified populations
Knowledge applied to plan/evaluate strategies to prevent/manage disease in specific populations
What did Hippocrates do in 400BC
Made the link between disease and environmental influences
Father of epidemiology
What did Nightingale, Koch and Snow pioneer in 1800
Infectious disease epidemiology
What was the new type of epidemiology being investigated in 1900 before WWII
Non infectious disease epidemiology
What considerations were being made in epidemiology in 1900 after WWII
Consider deliberate spread as well as natural spread Chronic diseases Emergence of new diseases Eco epidemiology Molecular epidemiology
Describe the use of John Snow’s spot map
Locations of water pumps and incidences of cholera plotted on a map
Most cases around Pump A => most likely cause of epidemic
Handle removed => prevented further spread
What are the 5 main applications of epidemiology
Community diagnosis Measure risk Assessment, evaluation, research Identify syndrome Find causes
What are the 5 main areas in epidemiology
What do they do
Descriptive
-examination of frequency/geographical areas over time
Aetiological
-study causes of disease
Evaluative
-effect of preventative measures on outcomes
Health services
-effect of outcomes and effectiveness of health services
Clinical
-natural course of disease and effects of diagnostic and procedures
What are the 3 main factors that relate to the causation of a disease
Based on the assumption that events => other events
Multicausality
- genetic
- environmental
Strength of cause
-when 1 cause has a greater effect than another
Induction time
-period of time between receipt of exposure and first presence of disorder
What is Rothman’s causal pie
Each contributory factor = pie slice
When the pie is complete => disease occurs
What are the 3 types of population considered in an epidemiological study
Target population
- total group of individuals from which the sample is drawn
- conclusions on population made from studies
Study population
-group of individuals in a study
Sample population
-subjects that provide data
What are the 3 measures considered in an epidemiological study
Measures of frequency
- prevalence
- incidence
Measures of association
Measures of impact
What 3 considerations do you have to make when measuring the prevalence of a disease
How do you measure prevalence
Existing cases
Population at risk
Time period where prevalence applies
(New and pre existing cases of diseases in given timeframe/Total population during same timeframe ) x 10^n
What 3 considerations do you have to make when measuring the incidence of a disease
How do you measure incidence
New cases
Population at risk
Timeframe
(Total no of new cases of a disease in a time frame/Total population at risk in same timeframe
0 x 100^n
What 3 considerations do you have to make when measuring the associations in a disease
What is association
Relative risk
Risk ratio
Odds ratio
Assess strength between variables
What 2 considerations do you have to make when measuring the impact of a disease
What is impact
Attributable risk
Vaccine efficacy and effectiveness
Impact of disease in population
Impact of eliminating risk factors
What are the 8 disease frequency components
- Categorise disease
- What is considered a true case of disease
- How to ascertain cases
- Define population at risk
- Define timeframe at risk
- Consent to study people
- Measure disease frequency
- Relate frequency to population and time at risk
How do you measure the cumulative incidence of disease in a group
(No of people with disease + factor)/(No of people with factor) x 100
How do you measure the risk ratio / cumulative incidence ratio
(Cumulative incidence of disease in people with factor)/(Cumulative incidence of disease in people without factor)
How do you measure the risk difference
(Cumulative incidence of disease in people with factor) - (Cumulative incidence of disease in people without factor)
How do you measure the odds ratio
(Disease and factor) x (No disease and no factor)/(No disease and factor) x (Disease and no factor)
AD/BC
How do you measure the potential impact
What is the significance of this value
Attributable risk/Incidence exposed x 100 = AR%
Attributable risk = Incidence exposed - Incidence unexposed
Gives you a percentage of how many cases are attributable to 1 cause
If not 100%, other factors are responsible
What are the 2 types of epidemiological investigtaion
Descriptive
Analytical
Describe the 3 characteristics of a descriptive investigation
Name the 6 applications
Patterns of disease occurrence
By person, time, place
Data easily accessed
Vital stats Periodic surveys Comparisons Program planning Hypotheses generation Future research
Describe the 3 characteristics of an analytical investigation
Name the 4 applications
Disease etiology focused
Resource intensive
Use comparison groups
Determinants of disease
Find risk factors
Hypotheses testing
Modes of transmission
What is the epidemiological triad
What is the significance of it
Place
Person
Time
Helps us understand distribution of disease
What are the 2 types of epidemiological study designs
Experimental
-shows that A=>B
Observational
-No manipulation of factors
What are the 4 properties of experimental epidemiological study designs
What are the 2 concerns of this design
Manipulation
Control
Randomization
Blinding
Unethical to cause disease
Not always feasible
What are the 4 properties of observational epidemiological study designs
What are the 3 concerns of this design
Non experimental
Non controlled
Natural grouping
Concept of time
Confounders
Selection bias
Measurement errors
How does the cost of a study relate to the validity
The greater the cost => the greater the validity
-Interventional trials are generally the best
What are the 3 main sources of error in studies
Selection bias
Information bias
Confounders
What are the 4 forms of selection bias in study errors
Self selection
Non response to interviews
Attrition, not everyone continues to take part
Selection survival, healthier people generally stay
What are the 3 forms of information bias in study errors
Reporting bias, memory issues
False -ve/+ve, diagnostic errors
Error and omissions in medical records
What are the main confounders in studies
Differences in age, gender, health status
What can confounders cause
False associations
False lack of an association
Under/overestimate of an effect
How do you reduce the effect of confounders
Randomising individuals
Filter out groups
Stratify analysis
What are the 2 main types of data source
Aggregate data
-generally easier to obtain
Individual level data
- can be obtained but not as easily
- generally needs consent
What are 4 examples of aggregate data
Vital stats
Census
Disease registries
Monitoring systems
What are 5 examples of individual level data
Vital events Disease registries Medical records National surveys Questionnaire data
What are the 4 main ethical issues regarding epidemiological research
Confidentiality
-need consent to gather info except in public emergency
Autonomy
Justice
-people being tested must benefit themselves
Beneficence
- minimise harm
- maximise benefit
