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BASIC PRINCIPLES OF EPIDEMIOLOGY

Epidemiology is the study of the determinants, occurrence, and distribution of health and disease in a defined population. Infection is the replication of organisms in host tissue, which may cause disease. A carrier is an individual with no overt disease who harbors infectious organisms. Dissemination is the spread of the organism in the environment.

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BASIC PRINCIPLES OF EPIDEMIOLOGY

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  1. An Introduction to the Basic Principles of Epidemiology Professor Dr. AB Rajar, MBBS, Dip-Diab, MPH, Ph.D.CPHE Director of Research and Innovative Center [IBN-E-SINA UNIVERSITY] Professor Dr AB Rajar

  2. LEARNING OBJECTIVES • At the end of this lecture, the students of the 4th year MBBS will be able to understand: • Introduction. • Modern epidemiology • Definitions and their components. • Aims of epidemiology • Uses of epidemiology • Scope of epidemiology. • Basic Measurements in Epidemiology • Tools of measurements Professor Dr AB Rajar

  3. EPIDEMIOLOGY Professor Dr AB Rajar

  4. INTRODUCTION • Epidemiology is the basic science of Preventive and Social Medicine. • Epidemiology is the scientific discipline of public health to study diseases in the communityto acquire knowledge for the health care of society including: • Prevention • Control • Treatment Professor Dr AB Rajar

  5. INTRODUCTION Professor Dr AB Rajar

  6. MODERN EPIDEMIOLOGY Professor Dr AB Rajar

  7. DEFINITION 1 2 3 • "The study of the distribution and determinantsof health-related statesor eventsin specified populations, and the application of this study to the preventionand controlof health problems ". 4 5 6 Professor Dr AB Rajar

  8. COMPONENTS OF DEFINITION. • Study: • Systematic collection, analysis, and interpretation of data. • Including observation, hypothesis testing, analytical research, and experiments. 1 Professor Dr AB Rajar

  9. COMPONENTS OF DEFINITION. • Distribution: • Refer to the analysis of an event by person, place & time Epidemiology studies the distribution of diseases it answers the question: • Who, where, and when? • Who? Where? When. 2 Professor Dr AB Rajar

  10. COMPONENTS OF DEFINITION. Epidemiology is concerned with the frequency and pattern of health events in a population. • A-Frequency: • refers not only to the number of cases but also to the relationship between the number of cases and the size of the population • B-Pattern: • Refers to the occurrence of health-related events by time, place, and person. 2 Professor Dr AB Rajar

  11. COMPONENTS OF DEFINITION. • Time patterns may be: • annual, • seasonal, • weekly, • or daily. • Place patterns include: • geographic variation, • urban/rural differences, • and location of work sites or schools. • Personal characteristics such as age, sex, marital status, and socioeconomic status, as well as behaviors and environmental exposures. Professor Dr AB Rajar

  12. COMPONENTS OF DEFINITION. • Determinant: • It is any factor that influences health as chemical, physical, social, biological, economic, genetic, or behavioral. • Epidemiology is also used to search for determinants, which are the causes and other factors that influence the occurrence of disease and other health-related events. 3 Professor Dr AB Rajar

  13. COMPONENTS OF DEFINITION. • To search for these determinants, epidemiologists use analytic epidemiology or epidemiologic studies to provide the "Why?" and "How?" of such events. Why? How? Professor Dr AB Rajar

  14. COMPONENTS OF DEFINITION. • Health-related state or event : • It is defined as anything that affects the well-being of a population. • As: disease, cause of death, behaviors, etc. 4 Professor Dr AB Rajar

  15. COMPONENTS OF DEFINITION. • Specified populations : • Although epidemiologists and direct healthcare providers (clinicians) are both concerned with the occurrence and control of disease, they differ greatly in how they view "the patient." • The clinician is concerned about the health of an individual. • The epidemiologist is concerned about the collective health of the people in a community or population. 5 Professor Dr AB Rajar

  16. COMPONENTS OF DEFINITION. • Application of this study to the control: • Epidemiological studies have direct and practical applications for the prevention of diseases & promotion of health Epidemiology is a science and practice Epidemiology is an applied science. 6 Professor Dr AB Rajar

  17. BASIC CONCEPT • Risk: The probability of having a bad outcome. • Risk factors: A condition, physical characteristic, or behavior that increases the probability that a currently healthy individual will develop a particular disease. " Professor Dr AB Rajar

  18. BASIC CONCEPT • Modifiable risk factors: • A risk factor that can be reduced or controlled by intervention, thereby reducing the probability of disease. • As : (Physical inactivity, Tobacco use, AIcohoI use, Unhealthy diets). • Non-modifiable risk factors: • A risk factor that cannot be reduced or controlled by intervention, for example, Age, Gender, Race, or Family history (genetics). Professor Dr AB Rajar

  19. ULTIMATE AIM OF EPIDEMIOLOGY • To eliminate or reduce the health problems of the community. • To promote the health and well-being of society as a whole. Professor Dr AB Rajar

  20. AIMS & OBJECTIVES OF EPIDEMIOLOGY • To describe the distribution and magnitudeof health and disease problems in the human population. • To identify etiological factors (risk factors) in the pathogenesis of the disease. • To provide data essential to the planning, implementation, and evaluation of services for the prevention, control, and treatment of disease and setting priorities among those services. Professor Dr AB Rajar

  21. SCOPE OF EPIDEMIOLOGY Professor Dr AB Rajar

  22. CAUSATION OF THE DISEASE. • Most diseases are caused by interaction between genetic and environmentalfactors. (Diabetes) • Personal behaviors affect this interplay. • Epidemiology is used to study their influence and the effects of preventive interventions through health promotion. Professor Dr AB Rajar

  23. 1-CAUSATION OF THE DISEASE. Professor Dr AB Rajar

  24. 2-NATURAL HISTORY OF THE DISEASE • Epidemiology is also concerned with the course and outcome(natural history) of diseases in individuals and groups. Professor Dr AB Rajar

  25. 2-Natural History of the Disease Professor Dr AB Rajar

  26. 3-HEALTH STATUS OF THE POPULATION • Epidemiology is often used to describe the health status of the population. • Knowledge of the disease burden in populations is essential for health authorities. • To use limited resourcesto the best possible effect by identifying priority health programs for prevention and care. Professor Dr AB Rajar

  27. 3- THE HEALTH STATUS OF THE POPULATION Professor Dr AB Rajar

  28. 4. EVALUATION OF THE INTERVENTIONS • To evaluate the effectiveness and efficiency of health services. • This means determining things such as — • Impact of Contraceptive use on Population Control. • The efficiency of sanitation measures to control diarrheal diseases and • The impact of reducing lead additives in petrol. Professor Dr AB Rajar

  29. 4-EVALUATION OF INTERVENTIONS Professor Dr AB Rajar

  30. CLINICAL EPIDEMIOLOGY • Applying epidemiological principles and methods to problems encountered in the practice of medicinehas led to the development of- Professor Dr AB Rajar

  31. APPLICATIONS OF EPIDEMIOLOGY IN PUBLIC HEALTH • Preventingdisease and promoting health. • Community health assessment (Community Diagnosis) and priority setting. • Improving diagnosis. treatment and prognosisof clinical diseases. • Evaluating health interventions and programs. Professor Dr AB Rajar

  32. EPIDEMIOLOGY AND PUBLIC HEALTH • Public health, refers to collective actions to improve population health. • Epidemiology, one of the toolsfor improving public health, is used in several ways. Professor Dr AB Rajar

  33. EPIDEMIOLOGY & CLINICAL MEDICINE • 1. In Clinical Medicine the unit of studyis a 'case', but in Epidemiology the unit of study is a 'defined population ' or 'population at risk'. • Physician is concerned with the disease in the individual patient, whereas Epidemiologist is concerned with the disease pattern in the entire population. • So, Epidemiology is concerned with both the Sick & Healthy. Professor Dr AB Rajar

  34. EPIDEMIOLOGY & CLINICAL MEDICINE • 2 In Clinical Medicine, the physician seeks to diagnose for which he derives a prognosis and prescribes specific treatment. • The Epidemiologist is confronted with the relevant data derived from the particular epidemiological study. (Community Diagnosis) • He seeks to identify the source of infection, mode of transmission, and an etiological factor to determine future trends, prevention and control measures. Professor Dr AB Rajar

  35. EPIDEMIOLOGY & CLINICAL MEDICINE • 3. In Clinical Medicine patient comes to the Doctor. • Epidemiologist, goes to the community to find out the disease pattern and suspected causal factors in the question. Professor Dr AB Rajar

  36. EPIDEMIOLOGICAL APPROACH. Professor Dr AB Rajar

  37. 1. ASKING QUESTIONS Related to Health Events Related to Health Action What can be done to reduce the problem? How can be prevented in the future? What action should be taken by the community? What resources are required? How are activities to be organized? What difficulties may arise? • What is the event? (Problem) • What is magnitude? • Where did happen? • When did happen? • Who is affected? • Why did it happen? Epidemiology is "a means of learning by asking questions and getting answers that lead to further questions." Professor Dr AB Rajar

  38. These questions can be referred to as: Professor Dr AB Rajar

  39. 2. MAKING COMPARISONS • To find out the differences in the AGENT, HOST, and ENVIRONMENT conditions between the two groups. • Weighs. balances and contrastsgive clues to ETIOLOGICAL HYPOTHESIS. Professor Dr AB Rajar

  40. Professor Dr AB Rajar

  41. DEFINING HEALTH AND DISEASE. • Definition • “Health is a state of complete physical, mental, and social well-being and not merely the absence of disease or infirmity " (WHO in 1948) Professor Dr AB Rajar

  42. DEFINING HEALTH AND DISEASE. • This definition — criticized because of the difficulty in defining and measuring well-being — remains an ideal. • The World Health Assembly resolved in 1977 that all people should attain: • level of health permitting them to lead socially and economically productive lives by the year 2000. (Health for All by 2000) Professor Dr AB Rajar

  43. DEFINING HEALTH AND DISEASE. • Practical definitions of health and disease are needed in epidemiology, which concentrates on aspects of health that are easily measurable and amenable to improvement. • Definitions of health states used by epidemiologists tend to be simple, for example, • "disease present" or "disease absent' Professor Dr AB Rajar

  44. DEFINING HEALTH AND DISEASE. • There is often no clear distinction between normal and abnormal. • Especially, for normally distributed continuous variables that may be associated with several diseases. • • Examples: • Cut of point for Blood Pressure- HTN. • Cut of point of Hemoglobin- Anemia. • Normal Range of Blood Cholesterol. Professor Dr AB Rajar

  45. Professor Dr AB Rajar

  46. Professor Dr AB Rajar

  47. INCIDENCE AND PREVALENCE • These are fundamentally different ways of measuring disease frequency. • The incidence of disease represents the rate of occurrence of new casesarising in a given period in a specified population, while • Prevalence is the number of existing cases (old+ new) in a defined population at a given point in time. Professor Dr AB Rajar

  48. INCIDENCE • "Number of new cases occurring in a defined population during the specified period of time" • Incidence= Number of new cases during a given period / Population at risk x 1000. Professor Dr AB Rajar

  49. SPECIAL INCIDENCES Professor Dr AB Rajar

  50. PREVALENCE • Prevalence is the total no of existing cases ( old + new) in a defined population at a particular point in time or specified period. • Prevalence = Total no of cases at a given point in time / Estimated population at time x 100 Professor Dr AB Rajar

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