Unit 1 Flashcards
Epidemiology
The study of distribution of disease and determinants of disease frequency in populations
Goal of Epidemiology
Is to control health problems and improve health at the population level
Operationally
Counting the causes of morbidity and mortality
Determining variables associated with causes of morbidity and mortality
In operationally why identify factors that are causes?
They are potentially modifiable.
-Guiding and evaluation interventions to improve public health
Basic Assumptions of Epidemiology
1) Death disease and disability do not occur at random
2) There are causal factors that can be identified through the systematic investigations of human populations
3) Identifying these causal factors can lead to preventative intervention
Clinical and Research Concerns: Exposure
Good or bad: Chemical, biological, physical, psychological, educational etc.
Clinical and Research Concerns: Outcome
Good or bad: Disease, cure, improved attitude, longer life, better QOL
We generally know either the exposure or the outcome and_____________
Want to measure the other
Endemic
The usual occurrence of a disease in a given population
Epidemic
A meaningful increase in the occurrence of a disease in a given population
Pandemic
Spread of a disease across a large region or worldwide
Epidemiological Reasoning
1) Suscpicion of an E–> D relationship
2) Hypothesis formation
3) Test E–>D hypothesis
4 Rule out alternative explanations: Chance, bias, confounding
Epidemiology is fundamentally concerned with________
Populations
Measuring distributions of disease in populations and the factors associated with those distributions
Association
An identifiable relation between an exposure and a disease
Methodological question
How do we look for a cause
Ontological question
What is a cause
Ethical Question
How do we decide if there is enough evidence to act on a cause
What is a cause
A cause of a disease is an event condition or characteristic the preceded the disease and without chick the disease WOULD NOT have occurred at all or would not have occurred until some later time.
Criteria for assessing Causality
1) Strength of association
2) Dose-response relationship
3) Temporal Sequence
4) Biological credibility
5) Consistency of findings across studies
Strength of Association
Is there a strong E-D relationship
BUT doesn’t imply that a weak association cant be judged as cause and effect
Dose-Response Relationship
Does risk increase with increase exposure?
Temporal Sequence
E–> D
Does the exposure precede the disease
Biological Credibility
Is there a known biological basis for the relationship
BUT DEPENDS ON CURRENT STATE OF KNOWLEDGE
Consistency of Findings
Do multiple studies report similar findings
Studies can differ by:
Investigator
Methodology
Study population
Epidemiologic Approach
Identify DISEASE Identify EXPOSURE Statistical associations between E/D Hold constant factors that may be mixed up in this measure of association Inference causal association Recommend intervention
Risk Factor
A factor whic if present increases the probability of disease occurrence
- The exposure must precede disease onset
- Must be associated with an increase disease frequency
- Absence of error and bias
Quantification in Epidemiology
Measuring diesel occurrence is fundamentel.
4 Types of scales
Nominal Scale
Ordinal Scale
Interval
Ratio
Nominal Scale
Uses names
Ordinal Scale
Follows an order based on severity
Interval Scale
Follows a mathematical order but has NO TRUE ZERO
Ratio Scale
Follows a mathematical order HAS a defined true zero
Quantification in Epidemiology
Depending on the time element we can also quantify cases as prevalent or incident by measuring:
- Prevalence proportion
- Incidence rate
Prevalence Proportion
=#Cases/#person in population ) at a specific time
Specific time can be a point or period of time
Ex. 45 D1 students /105 have at least one active carie
Incidence Rate
=# of new cases of disease/population at risk) over a time period
Ex.
7 new cases of periodontal disease per 105 D1 in 2010
_____Is not a rate but ______ is and is not meaningful without a time unit
Prevalence
Incidence
Issues with Incidence and prevalence
How do we know someone is a case
How do we count population at risk
What specific time period
Evidence Based Dentistry
EBD is an approach to oral heath care that requires INTEGRATION clinically relevant SCIENTIFIC EVIDENCE, relating to the patients oral and medical condition and history with the DENTISTS CLINICAL EXPERTISE and the PATIENTS TREATMENT NEEDS AND PREFERENCES
EBD is based on 3 components
1) Best available scientific evidence
2) A dentists clincal skill and judgement
3) Patients needs and preferences
What approach does EBD take
Patient centered!
It is an approach to practice and to making clinical decision. Just one component used to arrive at the best treatment. Provides personalized dental care based on the most current scientific knowledge.
EBD IS:
Systematic approach to practicing good dentistry:
Provide right care
To the right patients
At the right time
EBD is NOT
- Cook Book Dentistry
- A standard of care
- Only about randomized trials (EBD process is not a rigid methodolical evaltion of scientific evidence)
- Impossible to practice
EBD: Outcome
Better quality of patient care and outcomes
-Evaluation of science underlying clinical care
-Quality of decision making
-Reduciton in variations in clinical practice
Improvements in research and dissemination of results
EBD can facilitate_______
BUT does not guarantee, making better declines in the provision of dental care
EBD Steps *5
1 Formulate a relevant question
2 Find the best available evidence
3 Review the evidence for its validity and applicability
4 Integrate the best research evidence with your clinical expertise and patients needs/desires
5 Evaluate your efforts
PICO
Anatomy of well formulated question:
P-population
I-intervention
C-comparison
O-Outcome
Quality of information (from best to worst 6)
1 RCT 2 We'll controlled cohort studies, case control and nonrandomize clinical trials 3 Cross sectional studies 4 Descriptive surveys 5 Case Reports 6 Personal opinion
Primary Source
Must be the first disclosure containing sufficient information to enable peers to assess obseravations repeat experiments and to evaluate intellectual processes
Secondary Source
Includes most books, review, articles, and indexes to the literature and usually summarize reviews or organize information
Conducting a Search
1 Defining the question
2 choosing a resource
3 Keyword vs classification systems
4 Search techniques
Defining the question
The most difficult step
PICO
Patient, intervention, comparison, outcomes
Boolean Operators
AND, OR, NOT
Truncation
Allow you to place a symbol at the end of a word which tells the engine to retrieve the word stem with different endings (usually an *)
Phrases
Use quotation marks this limits the results to the exact phrase
Parentheses
Use to appropriately group the terms and operators to control the order of the search
Explode
Instructs the search engine to retrieve the information with a broad subject heading that are broken down into narrower subject headings
Internal Validity
The degree to which the results of a study are likely to approximate the truth
External Validity
The extent to which the effects observed are applicable to a broader population
Inference can only correctly be made to the population from which the sample was drawn
We often leap to inference far beyond the targeted population
Observational Studeis
They observe the outcomes without intervening to affect them
Experimental Studies
The researcher manipulates the exposure(usually a drug or treatment) to compare it to the standard of care
Observational Studies (ex)
Cohort studies
Case Control Studies
Cross Sectional Studies
Cohort Studies
Subjects are selected based on their exposure status
2 Types of cohort studies
Prospective Cohort-compares disease prevalence in the exposed and unexposed
Retrospective cohort- They begin with the exposure of interest and probe back for exposure information
Advantages of Cohort Studies
Maintains temporal sequence (assesses exposure before outcome)
Good for assessing rare EXPOSURES and rapidly fatal disease
Can study multiple diseases/outcomes from a given exposure
Can calculate INCIDENCE among exposed and unexposed
Minimizes error in ascertainment of exposure(least prospective)
Provides complete description of experience after exposure including rate of progression and natural history of disease
Disadvantages of Cohort Studies
1) Expensive
2) Inefficient for rare diseases
3) Long follow up
4) Secular trends may influence behavior and study characteristics over time
5) Diagnostic trends
Cohort: Selection of “exposed” and “unexposed” depends on:
Research question
Ability to collect exposure and disease information
How common/rare the exposure
Unexposed
Similar to exposed other than exposure factor
Appropriate selection and investigation methods to avoid bias and confounding
Case-Control Studies
Subjects are selected based on their disease status
Case studies should theoretically mimic ________ studies
Cohort studies
In case control studies__________ are compared to________
Diseased people (cases) Non-diseased people (controls)
Cases and controls should be:
Different only on their past exposure
Case control Studies
Can demonstrate risk INDICATORS and not risk FACTORS due to the retrospective nature of the study design (temporality cannot be assessed)
Case Control Studies: Exposure
Cases and controls must have had an EQUAL CHANCE OF BEING EXPOSED
The exposure has to be assessed retrospectively and proportions of cases and controls who are exposed are unknown at the beginning of the study
Case Control Advantages
1) Efficient for rare diseases**
2) Relatively efficient in terms of time and money
3) Can study diseases with long latency period
4) Allow for the evaluation of multiple exposures that may increase risk for a specific disease
Case Control Studies: Disadvantages
1) cannot DIRECTLY compute incidence of diseases in exposed and non-exposed persons
2) Temporal relationship cannot be established wit certainty
3) Prone to errors in selection of cases/controls and in errors pertaining o the collection of information
4) Not optimal for rare exposures***
Case Control: Selection of Cases and Controls
?
Cases: Cases (disease) definition Diagnostic criteria Hospital based or population based Incident or prevalence
Controls:
Would be cases if had the disease
Potential for bias and confounding
Cross Sectional Studies
Selection of subjects based on neither exposure or disease status
- Most basic study design
- Point in time or snapshot information
- Subject selected without regards to exposure or disease status
- Does not need explained etiologic objectives
Cross Sectional Studies: Advantages
Sampling and analytic methods provide for statistically valid inference to populations
Exposure and disease are assessed at the individual level