Lecture 1 Introduction to Epidemiology.pptx

quick introduction to epidemiology

1. Introduction to epidemiology Richards Nkhata chiza. B.Sc. Bchm, Bphy, Dip: SLT, PgDip TM, Cert: GHSC-PSM, Cert: MCM, Cert: Dhis2, Cert: EDS. Master of science Epidemiology & Biostatics Candidate.

2. Objectives At the end of the lecture, students should be able to: – Define epidemiology – State the two assumptions of epidemiology – List three critical issues in epidemiology – Describe the branches of epidemiology – Describe the epidemiological approach – Describe Functions of epidemiology – Explain why epidemiology is called the basic science for Public Health Practice

3. 1. Definition What is Epidemiology? Epidemiology Epi’ - upon ‘Demos’ - population ‘ Logus ’ – study

4. Definition Study of the distribution and determinants of disease frequency in human populations ( Rothman et al, 2008 ) Study of the occurrence, distribution and determinants of health-related states in specified populations Study of the distribution and determinants of health-related states or events in specified populations, and the application of this study to the control of disease and other health problems ( WHO )

5. Definition Study of the occurrence and distribution and determinants of disease and health-related states or events in specified populations, and the application of this study to the control of disease and other health problems ( WHO )

6. Definition….. Study of the occurrence of disease in human population Study of the distribution and determinants of disease frequency in human populations in order to reduce the frequency of disease

7. Definition…… "Epidemiology is a set of methods as well as an approach for judging the significance of data Epidemiology is also knowledge that is accumulated over the years about the characteristics and determinants of specific diseases or health conditions .

8. 2. Epidemiological assumptions Epidemiology is based on 2 fundamental assumptions: Disease does not occur at random SOME PEOPLE ARE MORE LIKELY TO GET THE DISEASE THAN OTHERS Comparison of groups in the population can identify underlying causes of the occurrence of disease

9. DISEASE DOES NOT OCCUR AT RANDOM SOME PEOPLE ARE MORE LIKELY TO GET THE DISEASE THAN OTHERS

10. Comparison of groups in the population

11. 3. Three Critical Issues in Epidemiology 1. Producing evidence – research (systematic reviews) 2. Making evidence available 3. Using evidence Evidence will accelerate uptake of results by authorities?? Not always the case

12. Branches of Epidemiology Field Epidemiology Clinical Epidemiology Reproductive Epidemiology Genetic/ Molecular epidemiology Environmental Epidemiology Disease Epidemiology Communicable disease Epidemiology Non communicable disease epidemiology

13. 4. epidemiological approaches/stages Epidemiological stages Descriptive Analytical Interventional Nine important questions to ask

14. Outcome (Diarrhoea) Total Exposure Yes No Exposed (No taking contaminated water) 40 60 100 Not exposed ( contaminated water) 70 30 100 Total 110 90 200

15. 2 X 2 Contingency Table Outcome (Diarrhoea) Total Exposure Yes No Exposed (Contaminated water) 70 (A) 30 (B) 100 (A+B) Not exposed (no contaminated water) 40 © 60 (D) 100 (C+D) Total 110 (A+C) 90 (B+D) 200

16. Odds Ratio (OD) Odds of being exposed if one has the disease=A/C Odds of being exposed if one has no disease=B/D OR= A/C (/B/D) OR=AC X D/B OR=AD/BC OR=70X60 (30X40) OR.3.5

17. Epidemiological approach Descriptive stage Analytical stage Application stage Prevention of disease

18. Descriptive stage: Describe the problem

19. Case d efination : Identification and Magnitude Identification: What are the main health problems in the area? Magnitude: How many cases or health events are there?

20. Describe (Distribution) Distribution Time: when do the cases occur? Place: where do they occur? Person: who is affected? End result: hypothesis generation

21. Analytical stage Why does the problem occur Identification of possible causes

22. Apply and evaluate What kind of measures were taken to deal with the problem What results were achieved What else could be done?

23. Practice of Public Health Two main functions of epidemiology: Assessment Response

24. A. Assess Burden /magnitude of disease (priority setting) Trends of disease Risk factors (time, place, person)

25. RESPONSE 4. Policy development /laws / regulations recommendations 5. Interventions – provision and evaluation of health care services (promotive, preventive, curative) 6. Research

26. 4: Explain why epidemiology is considered a as basic science of public health

27. Broadening epidemiological concept in 20th century Originally: knowledge base for Public Health Care –identifying causes/risk factors. Expansion: From infectious diseases non-infectious disease 2. From public health clinical practice

28. Epidemiology vs Clinical Care: How to decide? CLINICIAN What disease has this patients and how can I treat him best? EPIDEMIOLOGIST Why is this patient having this disease, at this time at this place? How can I prevent others from having the same disease .

29. Strategies in clinical epidemiology similar Observation of events – symptom, sign, illness, diagnostic procedure, treatment in groups of individuals Comparison of rates in the event among the groups Inferences regarding the basis for any difference seen

30. Epidemiology as a basic science of Public health Epidemiology often called “the cornerstone” of public health It is the study of the distribution and determinants of diseases, health conditions, or events among populations and the application of that study to control health problems By applying the epidemiological concepts and principles, public health problems and issues One will understand the practice of epidemiology as it relates to real life Appreciation of public health programs and policies

31. Functions of epidemiology Core Functions of Epidemiology Public Health Surveillance Field investigation (outbreak investigation) Analytical studies, systematic reviews (design, conducting, analysis, interpretation, communication of findings) Evaluation: designing, managing and evaluation of interventions and programmes Linkages: evidence for Clinical decision making, Disease Prevention and Control, collaboration Policy development

32. Exposure Disease Total Yes NO Exposure 60 A 35 B 95 No exposure 40 C 65 D 105 100 A+C 100 B+D 200

33. Public Health Surveillance Description: Surveillance information flows from public and health care providers such as Clinicians Laboratories Hospitals Health departments Feedback flows from health departments back to public and health care providers

34. Functions of Epidemiology Decision Patient's Values Patients condition Clinical expertise Judgment Proficiency Source: JA Muir Grey: Evidence-based health care, 2001 Patients baseline risk

35. Due to advance in scientific knowledge more emphasis is now based on Evidence Decision Best available evidence Patient's Values Patients condition Clinical expertise Judgment Proficiency Source: JA Muir Grey: Evidence-based health care, 2001 Patients baseline risk

36. Process Observation of unusual event What is going? Investigation: Is the observed association real?

37. How to practice epidemiology Describe disease in populations Compare persons with disease and without disease

38. Continuous process: Reviewing evidence in the light of new evidence Decision Best available evidence Values Resources New evidence of good quality Revised decision

39. Evidence Values Resources Evidence Values Resources Generating evidence and knowledge facilitates shift from Opinion-based decision-making to Evidence-Based Decision-making (EBD)

40. Hierarchy: Studies for building up evidence of observed association associated with increasing knowledge of the disease Increasing knowledge on the disease

41. Summary: Scope of evidence-based health care 1. Producing evidence – research – systematic reviews 2. Making evidence available 3. Using evidence

42. END OF PRESENTATION “SHUKRAN ; LAK BARAK; ALLAH-FIK