Epi Final Prep
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 "more dangerous bias" 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 > white males (60%) > black females > 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 Loss to Follow up 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). Leads to potential bias 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) > Major salivary glands (75%) > 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 "less dangerous bias" |
| 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 > 0: positive association (increased risk) RD < 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 < 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 >=30 subjects Normal distribution Use anova, ancova, or linear regression |
| What type of alcohol creates a "j" 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 > localized (earliest stage) > distan > 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 >= 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 >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 < 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 Adverse exposures seen 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 "at risk" 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 < Chronic periodontitis < Aggressive periodontitis < periodontitis modified by systemic influences < 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>1 means positive association POR<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 "less dangerous bias" |
| 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 "more dangerous bias" 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) Long periods of follow up 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 >= 5mm, with 1+ sites >= 4mm 2+ teeth with LPA >= 6mm, with 1+ >= 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 One received normal Swedish diet 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 < 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: Data is readily available Can be done quickly and inexpensively Weakness Can't link 2 issues at hand Can't link exposure with disease in particular individuals Can't control for confounding Can't disentangle complicated relationships |
| Epstein-Barr and oral cancer | Epsten barr leads to nasopharynx cancer |
| What is the leading cause of death in elderly? | Heart disease > Cancer > Stroke > Chronic Obstructive disease > Pneumonia > diabetes |
| Mortality of Oral/Pharyngeal Cancer and Race | Black males > White males > black females > white females |
