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Population Health for Health Professionals. Module 2 Epidemiology The Basic Science of Public Health.

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Presentation on theme: "Population Health for Health Professionals. Module 2 Epidemiology The Basic Science of Public Health."— Presentation transcript:

1 Population Health for Health Professionals

2 Module 2 Epidemiology The Basic Science of Public Health

3 OBJECTIVES l epidemiology and role as foundation for public health l common measures of disease frequency l strengths and weaknesses of study designs l applications of epidemiologic method

4 Part I Key Terms and Measures

5 Epidemiology l Study of distribution of determinants and antecedents of health and disease in human populations l Application of results to control of health problems

6 From Hippocrates to John Graunt l Fifth century BCE, Hippocrates pointed to the need to understand the environment and the risks it posed to understand the experience of disease l 1662, John Graunt analyzed weekly reports of births and deaths in London, quantifying patterns of disease in the population

7 From William Farr to John Snow l 200 years later, Dr. William Farr was made responsible for medical statistics in the Office of the Registrar General for England and Wales l A mere 20 years later, John Snow completed his study of cholera

8 Modern Experiences l Evaluation of risk factors for chronic diseases using case controls l Long term population studies using cohorts l Design of clinical trials to evaluate interventions

9 Three Essential Components l Disease distribution l Disease determinants l Disease frequency s Expected level s Endemic s Sporadic s Epidemic s Pandemic

10 Epidemiologic Studies l Descriptive l Analytic

11 Descriptive Studies l Frequency of occurrence of particular condition l Patterns of occurrence according to person, place and time

12 Analytic Studies l Observational studies s case-control studies s cohort studies u prospective u retrospective l Experimental studies

13 Case Control Study Key Basis for selection of group for study = present = absent ExposureDisease ? ?

14 Key Basis for selection of group for study = present= absent Prospective Cohort Study ? ? ExposureDisease

15 Retrospective Cohort Study Key Basis of selection of group for study = present = absent ? ? ExposureDisease

16 Analytic Studies l Observational studies l Experimental studies s Intervention studies s Clinical trials

17 Basic Presentation of Results All rates and ratios discussed can be calculated from this.

18 Smoking and Carcinoma of the Lung

19 Interpreting Results: Measurement Errors l Bias s information s selection l Confounding s extraneous factors l Effect modification s statistical interaction

20 Interpreting Results: Cause- Effect Relationship l Strength of the association l Consistency l Temporality l Plausibility l Biological gradient

21 Measures of Disease Frequency l Prevalence l Incidence

22 Prevalence l Prevalence= number of existing cases divided by total population s Visual examination survey 310 X 100 = 12.5% 2477

23 Types of Prevalence Measures

24 Incidence l Incidence = number of new cases in a given period of time divided by the total population at risk s Bacteremia among contraceptive users u 27/483 X 100 = 5.6%

25 Types of Incidence Measures

26 Rates Commonly Used in Epidemiology l Crude l Category specific l Age adjusted

27 Module Author Fran C. Wheeler, Ph.D School of Public Health University of South Carolina


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