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Introduction to Epidemiology.ppt
- 1. Introduction to the Fundamentals of Epidemiology
- 2. Question ?? What is different between Disease and Health?
- 3. What are disease and health? Dorland's Illustrated Medical Dictionary (28th ed.): Disease "any deviation from or interruption of the normal structure or function of any part, organ, or system (or combination thereof) of the body that is manifested by a characteristic set of symptoms and signs . . .". Health "a state of optimal physical, mental, and social well-being, and not merely the absence of disease and infirmity."
- 5. What is Epidemiology? Greek (English) epi (among) demos (people) logy (study)
- 6. Epidemiology Epidemiology is the study of the determinants, distribution, and frequency of disease Who gets disease and why Epidemiologists study sick and well people to determine the crucial difference between those who get disease and those who are spared
- 7. Epidemiology ... .... allows the distribution of health and ill- health in a population to be described in terms of WHAT is the problem and its frequency? WHO is affected? WHERE and WHEN does it occur? WHY does it occur in this particular population?
- 8. Example: John Snow John Snow, physician(1813-1858) Outbreaks of Cholera were common in London during the 19th century But what was causing the cholera? The popular theory at the time was that bad gases caused it (miasma theory)
- 9. What did he do? Analysis by place: he mapped the cases most were near Broad Street Anecdote: People had complained that the water smelt bad. Cases from further afield had water delivered by cart from Broad Street.
- 10. The early daysJohn Snow and the Broad Street Pub
- 11. The early daysJohn Snow and the Broad Street Pump
- 12. What did he do? Recorded deaths by water supplier Conclusion: Risk of infection is highest in people using water Southwark and Vauxhall water company .
- 13. Public health action He removed the handle from the Broad Street pump and the number of infections fell.
- 14. Epidemiology Is it a science? Or is it a method?
- 15. Is Epidemiology a Science? Science is a creative endeavor It relies on questioning, imagination, exploration It seeks out empirical evidence It tests ideas Study questions Hypotheses
- 16. Epidemiology Epidemiology weighs and balances Epidemiology contrasts and compares Epidemiologists use RATES events/population at risk
- 17. Epidemiology Numerator the number of people to whom something happened (i.e. they got sick, died, etc.) Denominator the population at risk -- all the people at risk for the event
- 18. What is Epidemiology? Some describe it as the study of epidemics What is an epidemic? An epidemic occurs when there are significantly more cases of the same disease than past experience would have predicted.
- 19. Uses of Epidemiology To study the cause (or etiology) of disease(s), or conditions, disorders, disabilities, etc. determine the primary agent responsible or ascertain causative factors determine the characteristics of the agent or causative factors define the mode of transmission determine contributing factors identify and determine geographic patterns
- 20. Uses of Epidemiology To determine, describe, and report on the natural course of disease, disability, injury, and death. To aid in the planning and development of health services and programs To provide administrative and planning data
- 21. Example: Use of Epidemiology In Sudan, the National Center for Health Statistics is a data source for information on health and disease http://www.fmoh.gov.sd/nchs Globally, the World Health Organization is a data source for information on health and disease http://www.who.int
- 22. Purpose of Epidemiology To provide a basis for developing disease control and prevention measures for groups at risk. This translates into developing measures to prevent or control disease.
- 23. Forms of Epidemiology Clinical Epidemiology Descriptive Epidemiology Predictive Epidemiology Etiologic Epidemiology Genetic Epidemiology Occupational Epidemiology Social Epidemiology Spatial Epidemiology Surveillance etc
- 24. Two Broad Types of Epidemiology Descriptive Epidemiology Examining the distribution of disease in a population, and observing the basic features of its distribution Analytic Epidemiology Testing a hypothesis about the cause of disease by studying how exposures relate to the disease
- 25. Descriptive epidemiology: applications studying the frequency and distribution of disease to generate hypotheses about causes (the academic focus) to inform local public health action (the service focus)
- 26. Descriptive Epidemiology is the Antecedent to Analytical Epidemiology Analytic epidemiology studies require information to . know where to look know what to control for develop viable hypotheses
- 27. Three essential characteristics of disease that we look for in descriptive studies are... Person Place Time
- 28. Person Age, gender, ethnicity Genetic predisposition Concurrent disease Diet, exercise, smoking Risk taking behavior SES, education, occupation
- 29. Place Geographic place presence or agents or vectors climate geology population density economic development nutritional practices medical practices
- 30. Time Calendar Time Time since an event Physiologic cycles Age (time since birth) Seasonality Temporal trends
- 31. Example You have been asked to investigate an event in which 2,220 people were exposed and 1,520 of them died. Your role as an epidemiologist is to ask questions about person, place and time.
- 32. How do we ask questions? Surveys -of survivors -of next-of-kin -of other related persons
- 33. with questions you learn that ... Person: Men, women and children were all exposed and at risk. The majority of people who died were wealthy and young men between 18-50 years (when compared to survivors). Place: All those exposed were within 1 block of one another, the climate was cold. Time: Mid April, people died within hours of the precipitating exposure.
- 34. Analytical epidemiology Descriptive epidemiology + Focus on cause and effect = analytical epidemiology
- 35. Three essential characteristics that are examined to study the cause(s) for disease in analytic epidemiology are... Host Agent Environment
- 37. The Epidemiologic Triangle Host Factors Personal traits behaviors genetic predisposition immunologic factors Agent Host Environment Influence the chance for disease or its severity
- 38. The Epidemiologic Triangle Agents Biological Physical Chemical Agent Host Environment Necessary for disease to occur
- 39. The Epidemiologic Triangle Environment External conditions Physical or biologic or social Agent Host Environment Contribute to the disease process
- 40. Epidemics arise when host, agent, and environmental factors are not in balance Due to new agent Due to change in existing agent (infectivity, pathogenicity, virulence) Due to change in number of susceptibles in the population Due to environmental changes that affect transmission of the agent or growth of the agent
- 41. Epidemiologic Activities are often framed under the mantle of descriptive and analytic epidemiology Descriptive epidemiology person, place & time Demographic distribution Geographic distribution Seasonal patterns etc. Frequency of disease patterns Useful for: Allocating resources Planning programs Hypotheses development
- 42. Epidemiologic Activities Analytic epidemiology built around the analysis of the relationship between two items Exposures Effects (disease) looking for determinants or possible causes of disease useful for: hypothesis testing
- 43. References Medical statistics at a glance Petrie and Sabin. Blackwell. Epidemiology in Medicine Charles Hennekins. Little, Brown and Company. Epidemiology for the uninitiated G.Rose and D.Barker. Health Knowledge website http://www.healthknowledge.org.uk