Lecture 2 Flashcards
The study of the distribution of disease and determinants of disease frequency in populations
Epidemiology
The study of “causes” of disease
Epidemiology
To control health problems and improve health at the population level
Goal of epidemiology
“Counting” the causes of morbidity and mortality.
Operationally
Determining variables associated with causes of morbidity and mortality
Operationally
- Identifying factors that are “causes” and are potentially modifiable.
- Guiding (and evaluating) interventions to improve public health.
Operationally
Do death. disease and disability occur at random?
No
Can be identified through the systematic investigation of human populations
Causal factors
What can lead to preventive intervention?
Identifying causal factors
Good or bad: Chemical, biological, physical, psychological, educational, etc
Exposure
Good or bad: disease, cure, improved attitude, longer life, better QOL (quality of life), etc.
Outcome
The usual occurrence of a disease in a given population
Endemic
A meaningful increase in the occurrence of a disease in a given population.
Epidemic
Spread of a disease across a large region or worldwide.
Pandemic
exposure of Interest
Independent variable
Outcome of interest
Dependent variable
Epidemiology is fundamentally concerned with
Populations
An identifiable relation between an exposure and a disease
Association
Xerostomia is _____ with higher caries incidence.
Associated
Incidence rate of oral and pharyngeal cancer is higher among smokers than among nonsmokers
Association example
How do we look for a cause?
Methodological question
What is a cause?
Ontological questions
How do we decide if there is enough evidence to act on a cause?
Ethical question
An event, condition, or characteristic that preceded the disease and without which the disease would not have occurred at all or would not have occurred until some later time.
Cause
- Strength of the association.
- Dose-response relationship.
- Temporal sequence.
- Biologic credibility.
- Consistency of findings across studies
Criteria for assessing causality
Is there a strong E – D relationship?
Smoking & lung cancer
Strength of association
Does risk increase with increased exposure?
Dose-Response Relationship
Does the exposure precede the disease?
Temporal sequence
Is there a known biologic basis for the relationship?
e.g., tobacco and lung cancer
Biologic credibility
What does biologic credibility depend on?
Current state of knowledge
Do multiple studies report similar findings regarding the E – D relationship?
(e.g., tobacco and lung cancer)
Consistency of findings
What can studies differ by?
- Investigator
- Methodology
- Study population
Identify a disease of interest.
Identify exposures of interest “risk factors”.
Statistical associations between exp. /disease.
Hold constant factors that may be “mixed up” in this measure of association.
Infer a causal association.
Recommend intervention
Epidemiologic approach
Measuring disease occurrence is fundamental in epidemiology.
Quantification in epideiology
4 types of scales in quantification
- Nominal Scale
- Ordinal
- Interval
- Ratio
Uses names
Nominal scale
Follows an order based on severity
Ordinal scale
Follows a mathematical order but has no true zero
Interval scale
Follows a mathematical order and has a defined true zero
Ratio scale
Depending on the time element we can also quantify cases as prevalent or incident by either measuring:
- Prevalence proportion
- Incidence rate
Equation for prevalance proportion
# of cases / # person in population (at a specific time)
Specified time interval can be a ‘point’ or ‘period’ of time
Prevalance proportion
Forty five (45) D1 students out of one hundred and five (105) have at least one active carious lesion
Prevalence proportion
Incidence rate equation
# of new cases of disease/population at risk (Over a time period)
7 new cases of periodontal disease per 105 D1 students in 2010.
Incidence rate
Is prevalence a rate?
NO
Is incidence a rate?
Yes
What does incidence need to be relevant
A time unit
Concerned with the number of new cases among persons at risk for a specific follow-up period
Incidence rates
With regards to diagnosis, prognosis or
causation, longitudinal studies such as _____________ are appropriate
Cohort studies
