##### Epi Final Prep
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#### Complete List of Terms and Definitions for Epi Final Prep

Terms Definitions
What can confounding lead to? Overestimate of true exposure-disease association

Underestimate of true exposure-disease association

Change in direction of the observed effect
Prevalence P = Incidence rate x mean duration of disease

Relates to an existing disease

Quantifies proportion of persons in a population at a specified period or point in time

Provides the probability that a person will be ill at that period or point in time

From equation: increase in prevalence could have resulted from increase in incidence or increase in disease duration or both
What is the common risk factor for oral and pharyngeal cancer in the US Heavy alcohol consumption

For 30 or more drinks, the OR is 9 for oral cancer
Observation analytical studies Analytical Study

Two types:
Case control studies
Cohort Studies
Measures of association Prevalence Odds Ratio (POR)

POR = (odds of exposure among diseased) / (odds of exposure among non-diseased

POR= (Odds of disease among exposed) / (odds of disease among unexposed)
Stratified Randomization Method to force the treatment

Groups are balanced on known suspected prognostic factors
Effects of nonrandom misclassification bias Exaggerate or underestimate true effects
&quot;more dangerous bias&quot; since you don't want to overestimate effect
Comparing rates across 2 populations If 2 populations have identical specific rates regarding a certain characteristic but different distribution of those characteristics then the crude rate can differ across the populaton
Trial on effect of NaF in Caries Clincal Trial
Double blind

Compliance assess by questionairre

Stratified randomization

Significance only seen in mesiodistal group aged 45-60
Category Specific Rate For either prevalence or incidence

Rate presented in specific category
(# of new cases in a specific group) / (at risk population in that specific group)
Type 1-error Alpha error

Finding difference when no difference exists
Adjusted rate Used for comparing rates across 2+ populations

Statistically constructed summary rate where difference in population distribution is taken into account

**When comparing rates adjusted for a particular variable, any remaining differences cannot be attributed to confounding by that variable
Survival from oral cancer based on race and gender White females &gt; white males (60%) &gt; black females &gt; black males
What is the strength/weaknesses of cross section surveys? Strength
Snapshot of population's health experience is seen at a specified time
Provides info on prevalence of health outcomes in certain groups or exposure patterns in certain groups
CAN test hypothesis

Weakness
Can't tell whether Exposure or Disease came first unless current value of exposure does not change over time (like eye color)
Negative Predictive Value The probability of not having the disease among those testing negative

From table
= d / (c+d)
= TN / (TN+FP)
What are measures of validity? Sensitivity
Specificity
Positive predictive value
Negative predictive value
In what population do 3/4 of oral cancers occur Occur in person 60+
Correlational study Based on data from a group or population

Correlates disease frequency in different groups at the same time
or in same population over time with some other factor of interest (consumption of certain food)
Association Measures the strength of the relationship between exposure and disease

EX: Relative risk and odds ratio
Screening The use of a test in asymptomatic persons to classify them to their likelihood of having a given disease

Allows Early detection of disease and assumes more favorable prognosis
Odds Ratio and Confounding If external factors (age/sex) odds ratio is less than the crude odds ratio, than confounding is indicated by the external factor
Misclassification bias Miscalculating or mismeasurement of exposure or disease

Some cases don't have the disease/exposure or some controls do have the disease/exposure

Types: Random and Nonrandom
Positive Predictive Value The probability of having the disease among those testing positive

From table
= a / (a+b)
= TP / (TP +FP)
What are the criteria for causality Strength of association

Dose-response relationship

Temporal Sequence

Biological credibility

Consistency across studies
What is the reason for the increase in elderly population? Increase in life expectancy

Decrease in birth rate, more people having fewer children

Baby boom phenomenon will turn 65 in 2011
Strength of association - criteria for causality The stronger the association, the less likely it is due to confounding

Measures include odds ratio, relative risk, and risk difference

A weak association DOES NOT necessarily mean that there is no cause and effect
Primary Levels of prevention Prevent the disease

Ex: Vaccines
Disadvantages of Cohort Study Time consuming
Expensive
Potential bias due to loss of follow up if people move away
Not suitable for rare disease outcomes unless disease is common among the exposed
Prevention trials Type of intervention study

Primary prevention

Study intervention to prevent the disease

Studied in individuals or communities
Mortality rates of Oral Cancer based on geography White males are higher risk along atlantic seaboard

White females are higher along east and west coastlines
Biological credibility - criteria for causality Biological mechanism is seen by which exposure affects the disease

Depends on the current state of knowledge
Nominal data no numeric relationship
Internal Validity The extent to which the effects detected in a study are truly caused by the treatment or exposure in the study sample, rather than being due to other biasing effects of extraneous variables
How to control confounding -Randomization
-Restriction of subject admission into the study
-Matching
-Stratified analysis or multivariable analysis
What is a cross over study Each subject serves as his own control

Requires a wash out period between treatment
Prevalence and Incidence according to Katz Prevalence = measurement of disease at 1 point in time

Incidence = measure of disease at 2 points in time
Probing Depths measured from free gingival margin to the base of the pocket
Dependent variable Response
Disease
Death
Misclassification bias- cohort study Misclassification of exposure/disease
Periodontal disease in the elderly Increases with age

6% in 25-35 years
41% among 65+ yrs
Type 2-error Beta error

Finding no difference when there's difference
Why is the a decline in caries in the US Fluoridation and toothpase were considered to be very important

Sugar, brushing and sealants were considered to be less important
Gingivitis Inflammation restricted to soft tissues
No loss of alveolar bone
No migration of periodontal attachment

Clinical signs = edema, erythema, gingival bleeding

Reversible with home care
How much sucrose is consumed per individual per year 30kg of sucrose in the US
47kg in Mexico
5kg in China
What are the bias in a Cohort Study Selection bias
Information bias
Misclassification bias
Non-participation
What is the causal model for caries Etiological factors like bacteria and sugar outweight preventative factors like fluoride and saliva
What is the life expectancy in the US Males 77.6
Females 80-85 years
Phase IV Therapeutic Trial Post marketing trials

Side effects studied
Therapeutic trials Type of intervention study

Secondary or tertiary prevention

Conducts in persons with disease
Determine ability of agent/procedure to diminsh sympons, prevent recurrence, and decrease mortality
Information bias - cohort study Expose/unexposed subjects remember/report exposure outcome differently
Recall bias Exposure info remembered or reported differently by cases and controls

Persons with disease are more likely than controls to think about or remember recall exposure therefore could lead to false findings
What occurs in unblended trials For unblended trials, both subjects and invetigators are aware of treatment assignment

This is because it may the only way to obtain study (ex surgery).

Subjects are more likely to drop out if they know their treatment assignment
Consistency across studies - criteria for causality Similar results are seen using different investigators, methods, and geography
Loss of Periodontal Attachment LPA

Measured from the CEJ to the base of the periodontal pocket
What is the dependent/independent variable variable Dependent - Disease
Independent - Exposure
What is the source of M. Streptococci in infants Mother

Similarity in bacteria genotype between mother and infact is seen in studies
Confounding Involves the possibility that an observed disease-exposure association is due totally or in part to the effects of differences between the study groups other than the exposure under study
What is the conventional model to caries prevention Treat clinical signs without addressing bacterial causes

Remove lesions and fill with inert material

Encourage patients to brush and floss while cutting down on snacks

Recall patients for evaluation and if caries found, blame the patient
Which locations have higher incident rates of oral cancer US, Canada and Brazil all have higher than median incident rates
Why does periodontitis occur Infectious disease
Failure to remove plaque
Host response
Destruction of soft tissue fibers
Pocket formation
Loss of periodontal attachement
Loss of alveolar bone loss
Tooth mobility
Faulty Inference Research may provide results that are not true

Due to chance, bias, confounding
Phase I Therapeutic Trial Primarily explore toxic effects, pharmacodynamics, pharmacokinetics

Less concerned with therapeutic effects, more with toxic effects
what is the reason for increased life expectancy Phase 1
Decline in infant mortality and death rates in children due to better prenatal and perinatal care

Phase 2
Decline in death rates among middle-aged and older people due to advances in medical care
Effect Modification The strength of the exposure-disease associatoon varies according to the level of the exposure of some other modifier

Can be seen when the ORs for confounder/effect modifier are different in magnitude
Power 1-beta error

Rejecting null when it's truly false and vice versa
What risk factor accounts for 75% of all oral cancer in US Smoking and drinking
Which measures of validity are desirable to be high? High sensitivity and specificity
What will the percent of elderly increase to in 2030 20%
Where: Descriptive Epi Considers where are disease rates highest/lowest based on locations, county/region, urban/rural
Sensititivy The probability of having a positive test among those with disease

The ability of a test to correctly screen all diseased individuals

From table
=a/(a+c)
=TN / (TP+FN)
I exposed Incidence of the exposed

From the table
I exposed = a / (a+b)

In other words, the # of individuals who have the disease and were exposed / total people exposed
KEOHS Project Cross sectional survey

-Kungholmen, Sweden
-129 dentate community
Found that having root caries is related to having coronal decay
-Can't generalize to other populations
-Can't tell whether exposure of disease came first
Antagonism Type of effect modification

The joint effect of A and B is less than the sum of their independent effects (A+B)
Survival from oral cancer 5 year survival rate
Lip (90% survival) &gt; Major salivary glands (75%) &gt; all others

The harder it is to see the area, the lower the survival rate
Accuracy Refers to the ability of a measurement to be correct on the average

If a measure is not accurate, it is biased
False Negative From table
= c

= 1 - sensitivity
Crude Rate For either prevalence of incidence

Weighted average of specific rate

Summary measure

(# of all NEW cases during a given period of time) / (TOTAL population at risk)
What are some measures of association Relative risk
Risk difference
Attributable risk percent
Effects of random misclassification Dilutes real effects
Biased toward no effect
&quot;less dangerous bias&quot;
Independent variable Exposure
Factor
Predictor
Risk difference Measure of association

RD = I exposed - I unexposed

Compares the risk of disease among the exposed to the risk of disease among the unexposed on a ABSOLUTE basis

RD = 0: no association
RD &gt; 0: positive association (increased risk)
RD &lt; 0: negative association (protective)
P- value p = 0.05

Use to assess statistical significance

Equals probability not measure of relation
Statistical significance Evaluates the role of chance
Phase II Therapeutic Trial Screening process for which drugs are effective

Determine if treatment has a preventive/therapeutic effect

Evaluate safety
Analytical Epi - according to Katz Goes after the why of the disease

Cross section, case control, cohort studies
Retrospective Cohort study When the study begins, the disease outcome AND exposure have already occurred

Requires high quality existing records

Less time, less expensive
Caries in Permanent Teeth - Adults Ecnomic factors and Mexican american problems still persist

Prevalence is about 90% of tthe poor and Mexican americans
False Positive From table
= b

= 1 - specificity
Dysplasia Histopathologic diagnosis characterized by cellular changes and maturational disturbances that can indicate a developing malignancy
Confidence Interval Suggest by how narrow or wide they are
How much power (ability to detect a difference in that sample) we have to detect difference

CI suggests how powerfule the study design was to detect a difference

CI = 0: no difference
CI = 1: not statistically significant

Wide CI may suggest no difference but raises concern that sample size was small
What is the most common site for oral cancer Tongue - lateral and ventral surfaces
next is tonsils
What are the risk factors for lip cancer Solar radiation
Tobacco
Low SES
Older age
Male
Periodontitis Inflammation extends beyond the gingival

Destruction of attachment and bony support

Clinical signs = loss of attachment, gingival recession, tooth migration, mobility, tooth loss

Can only be partially reversed
5 Aspects of Case Control Studies Case definition
Sources of cases
Prevalence versus incident cases
Sources of controls
Biases
Temporal Sequence - criteria for causality Which came first, exposure of disease?

Prospective cohorts studies are the best way to determine this
How can you increase PPV? Increase specificity or increase prevalence
What is the strength/weakness of population based source of controls? Strength
Aids generalizability

Weakness
Less motivated to do therefore quality of info is not as good
Logistically difficult
Expensive
Diagnosing Periodontitis Arbitrary cutoff of who's diseased
Different types of periodontal disease
Use probing
Life span The greatest age reached by any member of a species under ideal conditions and int he absence of disease

In humans, it is 120 ears
P value for statistically significant P value &lt; 0.05

P value says nothing on the quality of the study and the magnitude of difference
What is the rate of edentulism in older adults? 25-30%

Greatest in W. Virginia
Is there a risk of oral cancer associated with wearing dentures There is no excess risk
Observation Epi - according to Katz Descriptive + analytical
Analysis of continuous data Use T-test

Sample size &gt;=30 subjects
Normal distribution

Use anova, ancova, or linear regression
What type of alcohol creates a &quot;j&quot; type curve for risk of oral cancer? Wine

OR comes down before going back up
Root Caries Index DMF indices not used

Only 4 root surfaces per tooth

Takes into consideration root surfaces at risk

RCI =
[(root surface decayed + filled) / (root surface w/ gingival recession)] x 100%
Caries in the elderly Coronal caries increases in persons 75+

Root surface caries increase 3x with age
Randomization of Clinical Trials Study subjects are randomly assigned to one of the study groups

** each participant has the same probability of receiving each of the treatment
Prevalence study Cannot ordinarily determine a temporal relationship
Using odds ration to examine data Use if outcome is dichotomous

like yes/no
What is the most common type of oral cancer Squamous cell carcinomas
What is the stage of diagnosis most commonly seen Regional &gt; localized (earliest stage) &gt; distan &gt; unstaged
Loss to follow up bias - cohort study Large loss to follow up is cause of concern

Differential loss in exposed/unexposed groups

Lost subjectss repesent black box
Define Descriptive Epi Describes the distribution of disease in terms of who, where what and when
Compliance Important element of clinical trials

Relates to active participation, cooperation of study subjects

Noncompliance includes not taking medicines, obtaining alternative treatment, leaving the study

Non compliance reduces the chances of detecting any true effect of study treatment

Must select reliable and interested partcipants to prevent noncompliance

Compliance is measured by self reports, counting unused pills, biocheimcal measures
Prevalence of periodontal disease LPA &gt;= 3mm is 5.1% in ages 30-90

35% of US adults have periodontitis, with 21.8% having mild form
From the table a = true positive
b = false positive
c = false negative
d = true negative
If cause-effect relationship exists
AND
RD &gt;0
The value indicates the risk among the exposed that is attributable to the exposure or the number of cases of disease among the exposed that could be eliminated if the exposure was eliminated
What is considered successful aging Avoid disease, maintain high cognitive and physical function, engagement with life
What type of error is usually feared when a there is a new treatment vs placebo Alpha error
What is the strength and weakness of Case Control Study? Strength
Efficient for disease with long latency periods
Efficient for rare disease
Inexpensive
Time efficient
Allows for evaluation of multiple potential risk factors

Weakness
Somewhat more susceptible to bias because both exposure and disease occurred
Hard to establish temporal relationship
Can't estimate incidence rates
Not efficient on rare exposures
Can one epidemiological study establish causation? No
Cohort Study Analytical Epi study

Identify persons free of disease
Classify according to exposure status
Follow subject to assess the occurrence of the disease outcome

**Cohort studies dichotomize on exposure/independent variable

Types: Prospective and Retrospective
What study dichotomizes on exposure? Cohort Study
Bias Systemic error in the selection of subjects or collection of information on exposure and disease
Attributable Risk Percent Measure of Association

AR% = [(I exposed - I unexposed) / I exposed] x 100

AR% = (RD / I exposed) x 100

The portion of risk among the exposed that is attributable to the exposure
Cancer of the lip Males are more likely than females to develop lip cancer

Except in Thailand where females are more likely

Higher rates of lip cancer in Canada, Spain and Australia
Dose-response relationship - criteria for causality Does increased exposure = increased risk?
Red flag for bias If response rates among case and control groups are different
What happens to PPV and NPV when you increase sensitivity Little effects on PPV
What percent of the population is elderly? 13%
Confound Involves the possibility that an observed exposure-disease association is due to the effects of differences between the study groups other than the exposure under study
Definition of periodontitis (not severe) 3+ sites with CAL 4mm
AND
2+ sites with PD 3mm
The odds ratio in case control studies is a valid estimate for what? Relative risk
Selection bias Systematic difference in how cases, controls are enrolled

For it to occur, both exposure and disease must have occurred

Cases and controls are selected differently based on the exposure of interest

**Restricting study population based on one or more demographic characteristics is not selection bias
When: Descriptive Epi Considers when does disease occur

Whether it is seasonal

Also deals with frequency of disease from time to time
When do infants acquire M. Streptococci? First tooth at 7 months
M. Streptococci at 26 months
Case Control Study Observation Analytical Study

Study subjects are selected based on disease status

Compare the exposure patterns of persons in the case and control series

**They Dichotomize on disease of interest (the dependent variable)
Cumulative Incidence CI = (# of new cases of disease during given period of time) / (total population at risk

Provides an estimate of the probability or risk that a person will develop a disease during a specified period of time
Specificity The probability of having a negative test among those without the disease

The ability of a test to correctly identify those without disease

From table
= d / (b+d)
= TN / (TN + FP)
If cause-effect relationship exists and RD &lt; 0 The value indicates the reduction in risk among the exposed that is attributable to the exposure or the number of cases of the disease among the exposed tht was elimated by the exposure
What are the strengths/weaknesses of a correlational study? Strength
Recognition of new disease/epidemics
New therapies

Weakness
Findings may be coincidental since few cases are seen and no control/comparison group is used
Incidence Relates to new diseases

Quantify the # of NEW cases of disease that develop in an &quot;at risk&quot; population during a specified point of time

Two types of measures:
Cumulative incidence (CI)
Incidence density - not important
Intervention Studies Analytical Study

Allocate the exposure through a clinical trial
Advantages of Cohort Study Conceptually logical design
Temporal sequence more deeply established
Well suited for rare exposures
Prospective cohort is less prone to selection bias since for selection bias to occur, both exposure and disease have to have occurred
Allows for evaluation of multiple potential outcomes
Can directly estimate incidence rates and relative risks
What is the criteria for a confound? A confound is a factor that:
-must be an independent risk factor for disease
-must be associated with the exposure under study in the source population
-must not be an intermediate step in the causal pathway between the exposure and disease
Caries in Primary Teeth Study Observed caries increased with age

Observed caries high in Mexican Americans

Observed prevalenec is much lower for rich people than poor people and middle income
What is the order of periodontal disease Gingivitis &lt; Chronic periodontitis &lt; Aggressive periodontitis &lt; periodontitis modified by systemic influences &lt; necrotizing ulcerative periodontitis
Outcome ascertainment Important element of clinical trials

The quality of outcome info should be similar in all subgroups so observation bias is avoided

Follow up is complete for all study subjects

Isolate the treatment effect
Double blind design Both subjets and investigator are unaware of which treatment is being received

This is the standard

Reduces potential for observational bias

Difficult to blind both due to side effects

More complex and difficult to conduct
Prevalence Odds Ratio POR
Used as a measure of association
Ranges from 0 to infinity

POR=1 means no association (nullvalue)
POR&gt;1 means positive association
POR&lt;1 means negative association (protective association)

POR = (odds of exposure among diseased) / (odds of exposure among non-diseased

POR= (Odds of disease among exposed) / (odds of disease among unexposed)

From table = (a/c) / (b/d) = (a x d) / (b x c)

Ex: Odds ratio of 3 indicates the odds of being diseased among the exposed is 3 times the odds of being disease among the unexposed
Also, odds of being exposed among the diseased are 3 times the odds of being exposed among the non-diseased
How many new cases of oral cancer were in US in 2005? How many deaths due to oral cancer were they? 30,000 new cases

7000 deaths
Observation Studies Analytical Epi

Observe who's exposed/unexposed and who develops the disease
How to control for confounding Matching
-Forces case and control groups to be similar on specified characteristics
What is the strength/weakness of hospital based source of cases? Strength
Easy and inexpensive

Weakness
Not generalizable
Everyone's ill
Factors that lead to a particular hospital
Where is the highest distribution of elderlyy Florida
Pennsylvania
W Virginia
Iowa
N Dakota
Random Misclassification bias Degree of disease misclassification doesn't depend on exposure status (independent of exposure)

Degree of exposure misclassification doesn't depend on disease status

Effects:
Dilutes real effects
Biased toward no effect
&quot;less dangerous bias&quot;
Relative risk Measure of association

RR=(risk of disease among exposed) / (risk of disease among the unexposed)

RR=I exp / I unexpect

Many case control studies odds ratio provides a valid estimate for relative risk

RR of 2 means the risk of disease among exposed is 2 times the risk of disease among unexposed

Compares the risk of disease among the exposed to the risk of disease among the unexposed on a RELATIVE basis
What happens to PPV and NPV when you increase disease prevalence PPV increases

NPV decreases
Secondary Level of Prevention Catch the disease in early stages

Treat promtly

Ex: Identifying caries and restoring; screening
External Validity The extent to which study results can be generalized beyond the sample used in the study
DMF Index Decayed, missing, filled index

Related to either permanent teeth or surfaces

Decayed teeth takes precedence over filled surface

DMFT(eeth) = 0-32 teeth (or 28 if no 3rd molars)

DMFS(urface) = 148 surfaces (or 128 if not 3rd molars)
4 surfaces in anterior
5 surfaces in posterior

DMFS is greater than DMFT
Synergism Type of effect modification

The joint effect of A and B is greater than the sum of their independent effects (A+B)
Nonrandom misclassification bias Degree of disease misclassification depends on exposure status (dependent on exposure)

Degree of exposure misclassification depends on disease status

Effects:
Exaggerate or underestimate true effects
&quot;more dangerous bias&quot; since you don't want to overestimate effect
Prospective cohort study When the study begins, the disease outcome has not yet occurred (though exposures may have)

More control over info quality
Who is more likely to have gingivitis/periodontitis Older age
Male
Low SES
Smokers
Previous attachment loss
Uncontrolled diabetes
Specific bacterial species
Blocked Randomization Assigned in blocks

Avoids series imbalances in the # of each group

If Block size is small, then could one could predict the last treatment
What is the strength/weakness of hospital based source of controls? Strength
Easily identified
Similar recall

Weakness
hey are all ill therefore people with disease associated with exposure of interest should be excluded
Validity Measuring what you think you are measuring
BMI and oral cancer Inversely associated with risk of oral cancer

Thin = highest risk
Cancer of Oral cavity and Pharynx Males more likely than female

Highest rates in Somme, France and India
What is the use of descriptive epi? Provides clues about possible risk factors which can lead to hypothesis generation

Possible to ID populations with high or low risk disease therefore public health officials can use it to allocate resources
Simple Randomization Simple

Sometimes involves coin toss

Can result in unevent # of subjects in each group
Non-participation bias - cohort study Participants generally differ from non-participants

Influences generalizability
Which measure of validity is affected by disease prevalence PPV and NPV are affected by disease prevalence

Sensitivity and specificity are unaffected

Increase prevalence, increases PPV and decreases NPV

Increasing specificity, increases PPV
Ordinal data A graduation of extent, not exactly numerical

Ex: SES - poor, middle, rich
Periodontal indices Used to measure degree of periodontal disease thorugh pocket depth, plaque, gingivitis, bleeding, motility, and need for treatment

Gingival index goes 0-3

Periodontal index = 0, 1, 2, 4, 6, 8
Michigan Study Prospective study
Showed relationship between sugar and caries

Expected to see linear relationship since increased exposure should lead to increase disease

This was not observed

Relationship isn't totally linear because most likely it is linear in one section and then eventually plateaus
Tertiary Level of Prevention Limit the disability caused by the disease
Definition of severe periodontitis 4+ sites with LPA &gt;= 5mm, with 1+ sites &gt;= 4mm

2+ teeth with LPA &gt;= 6mm, with 1+ &gt;= 5mm
2 fold increase
3 fold increase
2 fold = 100% increase
3 fold = 200% increase
Vipeholm Study Dental caries clinical trial

Used patients in mental institute

Two controls used
Rest received vaying amounts of reducing sugars in diet

Conclusion
Means caries can still occur in absence of refined sugars but sugar consumption increases caries activity

Risk of caries is greater if sugar is retentive/sticky and if taken between meals

Caries risk disappears on withdrawal of sticky sugars
Which is worse: bias away from null or bias towards null Bias away from null is of greater concern than towards the null in a study
HPV and oral cancer HPV can lead to tonsilar and oropharynx cancer
Analysis of noncontinuous data Use if you have counts or proportions

Use chi-square test
What are the benefits to randomization Tends to produce study groups comparable with respect to known and unknown factors

Removes investigator bias in the allocation of treatment to particpats
How many errors can exist Only one type of error can exist
Only alpha or only beta error
Can poor hygiene lead to oral cancer OR = 2

People with oral cancer tend to have plaque that was able to metabolize alcohol into acid aldehyde which is carcinogenic
Life expectancy The average age reached by members of a population or the number of years an individual can expect to live
Does epidemiological data under or overestimate the true distribution and severity of periodontitis? It underestimates the true distribution
I unexposed Incidences of the unexposed

From the table
I unexposed = c / (c+d)

In other words, the # of people who have the disease and were NOT exposed / total # o people NOT exposed
What type of validity is generalizability External validity - The extent to which study results can be generalized beyond the sample used in the study
Null Hypothesis “There is no difference between [independent variable (a group exposed to)] regarding [dependent (diseased)] in [relevant population characteristics”

To be written of the whole article
All other questions of the LAF are to be written within section
Pair matching Match one on one
What are two goals of data collection and analysis Accuracy and precision
Why is geriatric important Increased number of older adults

Increased number of retained natural teeth

Increased utilization of dental services
Hawthorne Effect There is a change in behavior due to special attention given by being in a study
What is the weakness of DMF Index? Teeth lost to other diseases rather than caries is clumped

Don't always know the # of teeth at risk and age should be specific

Applies to coronal caries only

Becomes problem in mixed dentition with children
Case Reports/Case Series Uses detailed reports of unusual medical and dental occurrences from either one person (case study) or a group (case series)
What are important elements of clinical trials Randomization
Blinding
Compliance
Outcome ascertainment
What is the ethnicity of the elderly? 84% are non-hispanic whites

In 2050, there will be an increase in Hispanics and decrease in non-hispanic whites
What bacteria is causality for tooth decay Mutans streptococci
What is the trend of OR and the risk for oral cancer when drinking wine Wine forms a J curve

OR comes down before going back up
Vegetables and risk for oral cancer Eating higher levels of vegetables and fruits lowers risk of oral cancer
Dental insurance among the elderly Only 22% of older persons are covered by private dental insurance

Out of pocket is the mode of payment for oral health care by the elderly
What type of error is usually feared when there is an unattractive new treatment vs standard treament alpha error
What is the leading cause of death in US? Heart disease for both male and female
2nd: Cancer
3rd: Stroke
4th: Chronic obstructive pulmonary disease
5th: car accidents
Method of Case Control Study Hypothesize exposure/disease relationship

Identify persons with and without disease

Determine past exposure history through questions and medical records

Compare exposure history for cases and controls (ex: what fraction of cases exposed; what fraction of controls exposed)
Prevalence Rate P = (# of existing cases of disease at a given point in time) / (total population
Who : Descriptive Epi Considers who is getting the disease based on demographic factors, socioeconomic factors, lifestyle factors

Used to generate hypothesis
Phase III Therapeutic Trial Compare preventative/therapeutic strategy against a standard or placebo
What is the gender of the elderly? 145 women to every 100 men

Most males will still be married, while women are widowed and living alone
Association between saliva levels of M Streptococci and Caries High levels of salivary M. Streptococci = high DMFT and DMFS
What study dichotomizes on disease? Case Control studies
Method for Cohort Study Identify persons free of disease

Note exposure status

Follow over time to identify outcomes of disease

Compare rates of disease in two groups
Types of Effect modification Synergism

Anatgonism
What is the high rates of oral and pharyngeal cancer in India Due to areca nuts and betel leafs
Submucous fibrosis is a precancerous lesion as a result for chewing tobacco
OR from 100-250
Cross Sectional Surveys Use data from individuals
Exposure and disease are assessed together
Data sources are from national surveys to small surveys in small subpopulations
Either period prevalent or point prevalent
Caries in Permanent Teeth - Children Cross sectional study

Economic disparity still apparent

Mexican americans still have same problems as in primary teeth
Types of Analytical Epi Observation Studies
Intervention Studies
Observation Analytical Studies
What is the leading site-specific cause of cancer deaths in the US? Lung cancer for both males and females
What are the 5 criteria for causation Temporal relationship of exposure before disease

Strength of relationship - increased A leads to increased B

Specificity of relationship

Coherence of relationship

Consistency
Types of intervention studies Prevention trials

Therapeutic trials
Descriptive Epi - according to Katz Tells who, what, when, and where

Does not have a null hypothesis
Rare Rare = prevalent rate &lt; 10% of population
Blinding Element of a clinical trial

Treatment assignment is not known to certain people

Hard to do in certain cases to obtain consent
What is the strength/weakness of population based source of cases? Strength
Potential for generalizability

Weakness
Can't access patients fast enough
Logistically difficult to identify people
Expensive
What are prevalent oral conditions in the elderly Caries, periodontal disease, edentualism, oral cancer
Confounding and Effect Modifier THe presence/absence of confounding does not imply the presence/absence of effect modification and vise versa

Confounding is a problem with data that must be fixed

Effect modification is a reflection of nature that should be described
Kingston-Neuburgh Trial Water fluoridation community trial

Double blind

Newburgh was fluoridate
Kingston was not

Newburgh saw DMFT decrease
Kingston has constant DMFT
What happens to PPV and NPV when you increase specificity PPV icreases

Little effects on NPV
Selection bias - cohort study Occurs when subject's outcome influences his classification of exposure
or
the entry of exposed and unexposed subjects into the study is different based on disease outcome

Unlikely to occur in prospective cohort
May occur in retrospective cohort
Sugar consumption Cohort Study Sugar consumption is less important in relation to caries

Sugar consumption remains a caries risk factor for those susceptible to sugar-caries relationship
Frequency matching Distribution of characteristics are similar
Single blind design Subjects are unaware of treatment being received

Potential for observational/investigator bias

Look for objective outcome measures
What is the best way to determine temporal sequence of exposure and disease/ Through prospective cohort studies
Smoking and oral dysplasia Current smokers are 4x more likely to have oral dysplasia than non current smokers
What is the antimicrobial approach to caries prevention Block plaque buildup through GTF inhibition

Use mouthwash like chlorhexadine anf fluorides to combat bacteria

Break the chain of transmission

Alter immune response using caries vaccines

Alter oral ecology through replacement therapy
What type of error is usually feared when an attactive new treatment vs standard treatment Beta error
What is the trend of OR and the risk of oral cancer when drinking beer and hard liquour Have a stronger dose response relationship than J shape curve from wine
Continuous data Numerical from -infinity to +infinity

Can test tendency and variability
What are the strengths/weakness of a correlational study? Strength: