Module 1: What is Epidemiology?Epidemiology: The study of the distribution of health outcomes, risk factors and exposures in population. Public health: Promote the health of the population through organized community efforts 2 aspects of public health where epidemiology is used: 1. Prevention 2. InterventionEpidemiology: - the study of the distribution and determinants of the disease or health outcomes in specified populations, and the application of this study to the control of the health problems Epidemiology is used: - to develop, target, and evaluate prevention strategies 3 Levels of Public Health Prevention: 1) Primary Level: - occurs before the person gets the health outcome (or disease), ex. Vaccines 2) Secondary Level: - occurs after health outcome or (disease), but before symptom , ex. Checking for suspicious skin growths 3) Tertiary Level: - already has symptoms of the disease (or health outcomes),ex. Dietary advice to manage diabetes Epidemiology also used- to evaluate interventions in the populations 2 Levels of Public Health Interventions: 1) Individual Level: - refers to changing individual behavior or risk factors, ex. Educating individuals on the benefits of quitting smoking2) Structural Level: - promotes health by altering structural context, ex. Taxation of tobacco products Public Health is: Preventing illness and disability and prolonging life Promoting physical and mental health and efficiency Community efforts for sanitation of the environment Prevention of disease and injuries Education of the individual Organization of services for the diagnosis and treatment of disease Promoting a standard of living adequate for the maintenance of health

Understanding how behavior effects health promotion and disease prevention is important.

Person, Place, Time and Population Perspective

1) Descriptive epidemiology: Person Place Time Descriptive epidemiology: Frequency Distribution Of disease or risk factors in populations. Descriptive epidemiology: Evaluate trends Health status New diseases Evaluate public health programs Identify problems

2) Analytic Epidemiology: Risk factors Preventive factors What are the underlying causes of this pattern of disease? -use of comparison groupMeasures of Disease Frequency Epidemiologists study: Diseases in the population Health outcomes (diseases, illnesses, conditions, disorders, symptoms, behaviors, risk factors, injuries). Prevalence: Malaria infects 10% of the worlds population;

Prevalent vs. Incident Cases

Incident cases: - NEW cases of disease Prevalent cases: -ALL cases of disease (existing and new cases of disease)

2 types of Prevalence Measurements: 1) Point prevalence (May 1, 2012) Do you have asthma?2) Period Prevalence (Summer 2012) Have you had asthma during the past 3 yrs?Risks:Rates: Why use rates as a measure? Flexible Exact Capture reality of changing population Can study repeated events Odds: Will occur: will not occur Formula: p/(1-p) Ex: If the probability of an event is 0.20, then the odds are: 0.20/(1-0.20)= 0.25 or 1:4 0.33/(1-0.33)= 0.49

Experimental and Non-Experimental Study Designs: Experimental: ex - randomized control trials, clinical case cross-over. Investigator randomly assigns exposure. Observational /Non-Experimental: ex- case control, cohort, ecologic, cross-sectional. Observational, does not assign exposure. Experimental Study Designs: a) Randomized Control Trials: RTC Randomization helps to reduce or prevent bias. b) Cross over Clinical Trial Subjects switch from one treatment to the other.c) Blinding

Non-Experimental Study Designs:a) Cohort Study Design: Cohort- a group of persons sharing a common characteristic. Risk or Rate- common measure of disease occurrence in cohort study. 2 types of Cohort studies: 1) Retrospective and 2) Prospective

b) Case Control Study Design: Efficient method to study rare diseases Key steps: 1) Define and select cases, 2) Define and select controls, 3) Compare exposure prevalence Odds of exposure for cases : Odds for exposure for control

c) Cross-sectional Study Designs: Exposure and outcome are assessed at the same time Measure used to describe the occurrence is prevalence

d) Ecological Studies: Group level data

Measures of Association Measure of occurrence: Prevalence Risk Rate Odds Measure of occurrence: Compare measures of disease occurrence in two different groups, the exposed group and the unexposed group.Odds Ratio: