Epidemiology & Critical Thinking D. Morse st Avenue Tel: Office Hours: 4:00-5:00 (M & W)

Epidemiology & Critical Thinking Syllabus Readings –VitalBook –Required / Non-required readings Examinations –Mid-term 40% (10/14) –Final 60% (cumulative) (12/11) –Format Slides Notes

Epidemiology The study of the distribution determinants of disease in human populations

Epidemiology in Dentistry Which posterior composite holds up the best over time? Does fluoride prevent caries in older adults? –What about an OTC fluoride mouthrinse? –What about drinking fluoridated drinking water? –What about chlorhexidene rinses to prevent root caries? Does mouthwash use increase the risk of oral cancer? Does periodontal disease increase the risk of heart disease?

Past Achievements: Epidemiology & Oral Health Water fluoridation and dental caries Fluoridated toothpaste and dental caries in children Smoking and oral cancer

Past Achievements: Epidemiology & Oral Health Water fluoridation and dental caries Fluoridated toothpaste and dental caries in children Smoking and oral cancer

Past Achievements: Epidemiology & Oral Health Water fluoridation and dental caries Fluoridated toothpaste and dental caries in children Smoking and oral cancer

Epidemiologic Terms 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

Epidemiologic Terms Validity Generalizability Reliability

Statistical vs. Clinical Significance Statistical significance –Relates to the probability that chance is responsible of an observed difference –P-value or confidence interval –Sample size is important –Says nothing about Magnitude of difference Clinical relevance Quality of the study Clinical significance –Relates to whether the findings are important from a clinical standpoint

Independent vs. Dependent Variables Independent Variable: Exposure of Interest E  D Dependent Variable: Outcome of Interest E  D

Levels of Prevention Primary prevention –prevent the disease Secondary prevention –catch the disease early –prompt treatment Tertiary Prevention –limit disability

Generalized Relationship Between Stage of Disease / Ease of Detection / Ease of Cure Stage of Disease LowHigh Ease of CureEase of Detection Difficult Easy

Scope of Epidemiology Infectious disease epidemiology Chronic disease epidemiology Occupational epidemiology Clinical epidemiology Molecular epidemiology

Laboratory/Animal Model vs. Epidemiologic Research

Process of Epidemiologic Reasoning Suspicion of an E  D relationship Hypothesis formation Test E  D hypothesis Rule out alternative explanations –chance –bias –confounding

Criteria for Assessing Causality Strength of the association Dose-response relationship Temporal sequence Biologic credibility Consistency of findings across studies

Criteria for Assessing Cause-Effect Relationship Strength of the Association Is there a strong E – D relationship? (e.g., smoking and lung cancer) –Less likely due to uncontrolled confounding –Measures of association: OR, RR, RD But, doesn’t imply that a small association can’t be judged as cause and effect

Criteria for Assessing Cause-Effect Relationship Dose-Response Relationship Does risk increase with increased exposure? But, may be a threshold effect

Relative Risk of Lung Cancer by Level of Cigarette Smoking, Chinese Men Smoking Yrs Relative to lifelong nonsmokers

Temporal sequence Does the exposure precede the disease? Criteria for Assessing Cause-Effect Relationship

Biologic credibility Is there a known biologic basis for the relationship? (e.g., tobacco and lung cancer) But, depends on current state of knowledge Criteria for Assessing Cause-Effect Relationship

Consistency of findings across studies Do multiple studies report similar findings regarding the E – D relationship? (e.g., tobacco and lung cancer) Studies can differ by –investigator –methodology –study population Temporal sequence Criteria for Assessing Cause-Effect Relationship