Epidemiology basic concepts,scope,uses, consideration, components ,history and field of epidemiology.
- 2. 12/27/2023 2 Introduction • The term epidemiology is derived from the Greek word epidemic. – Epi means-Among, upon, – Demos means study population or people and – Logos means scientific study. • So – it is the scientific study of the disease pattern in human population. – In broad sense, it is the study of effects of multiple factors on human health. – It is multidisciplinary subject involving those of the physician, Biologists, Public Health experts, Health educators etc.
- 3. 12/27/2023 3 Definitions • The science of infective diseases, their prime causes, propagation and prevention. (Stallbrass 1931.) • The science of the mass phenomena of infectious diseases or the natural history of infectious diseases. (Frost 1927)
- 4. 12/27/2023 4 Definitions • The study of the disease, any diseases, as a mass phenomenon. (Greenwood 1935) • The study of condition known or reasonably supposed to influence the prevalence of disease. (Lumsden 1936) • Epidemiology as, study of the distribution and determinants of diseases frequency in man. (Mac Mohan and Pugh)
- 5. 12/27/2023 5 The widely accepted definition of epidemiology is, • "The study of the distribution and determinants of health related states or events in specified population and the application of the study to control of health problems“ (J.M. Last 1988)
- 6. 12/27/2023 6 Basic Tenets of epidemiology • Target of a study in epidemiology is human Population as Geographical area, Age, Sex, Ethnicity, Race etc.: the most common population in epidemiology is the population in a given area or country at a given time. Since the structure of population varies at each time such variations also have to be taken in to consideration during data analysis. • All findings must relate to the defined population. Enumeration is not enough in epidemiology, the population at risk of developing that diseases need to be enumerated as well.
- 7. 12/27/2023 7 Basic Tenets of epidemiology • Conclusions are based on comparisons: comparing the rates of diseases frequency among the exposed and unexposed is an important epidemiological method. • Description of events by time, place and person. Getting answer for when, where and who are affected is very important in epidemiology to formulate hypothesis about its causation. Other important aspects are what, why and how of the events.
- 8. 12/27/2023 8 Aims of Epidemiology According to the International Epidemiological Association (IEA) Epidemiology has three main aims. – To describe and analyze diseases occurrence and distribution in human populations; – To identify etiological factors in the pathogenesis of diseases; – To provide the data essential to the planning, implementation and evaluation of services for the prevention, control and treatment of diseases and to the setting up of priorities among those services.
- 9. 12/27/2023 9 The ultimate aims of epidemiology can be concluded in to two followings points. • To eliminate or reduce the health problem or its consequences and • To promote the health and wellbeing of society as a whole.
- 10. Scope of Epidemiology Originally, Epidemiology was concerned with investigation & management of epidemics of communicable diseases Lately, Epidemiology was extended to endemic communicable diseases and non- communicable infectious diseases 12/27/2023 10
- 11. 12/27/2023 11 Uses of epidemiology • Investigation of causation of disease. Genetic Factors Good Health Ill Health Environmental Factors
- 12. 12/27/2023 12 Uses of epidemiology • Study of the natural history and prognosis of diseases. Good health Sub clinical Changes Clinical Diseases Death Recovery
- 13. 12/27/2023 13 Uses of epidemiology • Description of the health status of the populations. It includes proportion with ill Health, change over time, change with age etc. • Evaluation of the interventions. • Planning health services, Public policy and programs.
- 14. 12/27/2023 14 And, Recently • epidemiologists have become involved in evaluation the effectiveness and efficacy of health services, by determining the appropriate length of stay in hospital for specific conditions, the value of treating High blood pressure, the efficiency of sanitation measures to control diarrhoeal diseases, the impact on public health of reducing lead activities in petrol etc.
- 15. 12/27/2023 15 Components of epidemiology Disease frequency: - • The core characteristics of epidemiology are to measure the frequency of diseases, disability or death in a specified population. it is always as the rate, ratio and proportion. • Much of the subject of epidemiology subject matter of measurement of diseases and health related events falls in the domain of biostatistics, which is a basic tool of epidemiology. This helps to development of strategies for prevention or control of health related problems.
- 16. 12/27/2023 16 Components of epidemiology Distribution of diseases: - • Health events occur in pattern in community and this pattern varies from community to community. • Also health events or diseases condition affect population at various age groups, different sexes, different subgroups of population. • Distributions of events are based on time, place, and person. We can analyze whether any increases or decreases occur for a particular condition. Epidemiology addresses itself to a study of these variations or patterns, which may suggest or lead to measure to control or prevent the diseases. An important outcome of this study is formulation of etiological hypothesis.
- 17. 12/27/2023 17 Components of epidemiology Determinants of diseases;- • Epidemiology helps in identifying the causative agent or the risk/predisposing factors of diseases . • This is one of the real uses of epidemiology. Understanding the factors leading to any programs for the control of those diseases.
- 18. 12/27/2023 18 History of epidemiology • The history of epidemiology has its origin in the idea, goes back to (400BC) Hippocrates through John Graunt (1662), William Farr, John Snow and others that environmental factors can influences the occurrences of diseases in stead of supernatural viewpoint of diseases. • John Graunt analysis and published the mortality data in 1662.He was the first quantify pattern of death, birth and diseases occurances. He is said to be the first to employ quantitative methods in describing populations vital statistics & has been referred to as the colombus of statistics. • No one built upon Graunt’s work until 1800’s.when William Farr began to systematically collect and analyst the Britain’s mortality statistics. Farr considered as the father of vital statistics and diseases classifications.
- 19. 12/27/2023 19 History of epidemiology • Meanwhile John Snow was conducting the series of investigations in London that later earned him the title father of field epidemiology. Snow conducted his classical study in 1854 when an epidemic of cholera developed in the golden square of London. During the time of microscope development, snow conducted studies of cholera outbreak both to discover the causes of diseases and prevent its recurrences. • During that time two men (Farr and snow) had major disagreement about the cause of cholera. Farr adhere to what was the called miasmatic theory of diseases, according to this theory which was commonly held at a time diseases was transmitted by a miasma or cloud that clung low on the earth surface.
- 20. 12/27/2023 20 History of epidemiology • However Snow did not agree he believed that cholera is transmitted through contaminated water. He began his investigation by determining where in this area person with cholera lived and worked. He then used this information to map for distribution of diseases. Snow believed that water was the source of infection for cholera. He marked the location and searches the relationship between cases and water sources. He found that cholera was transmitted though contaminated water. This was the major achievement in epidemiology.
- 21. 12/27/2023 21 History of epidemiology • In the 1900s epidemiologists extend their methods to noninfectious diseases and studied effect of behaviors and life style in human health. There are some important achievements in epidemiology they are; – John Snow and cholera epidemic in London in 1848-1854. – Framingham heart study started in 1950 in Massachusetts, USA and still continuing to identify the factors leading to the development of the coronary heart diseases. – Smoking and lung cancer by Doll and Hill in 1964. – Polio Salk vaccine field trial in 1954 to study the protective efficacy of vaccine in a million school children. – Methyl Mercury poisoning 1950s In Minamata
- 22. 12/27/2023 22 Field of epidemiology Epidemiology covers the various types of field in different types of activities. It is applied in every field as agricultural, economics, statistics etc. They are as • Clinical epidemiology • Geographical epidemiology • Social epidemiology • Statistical epidemiology • Descriptive epidemiology • Analytical epidemiology • Experimental epidemiology • Infectious diseases epidemiology etc.
- 23. 12/27/2023 23 Comparison between Clinical medicine and Epidemiology S. N. Area Epidemiology Clinical Medicine 1 Unit of study Population ( Defined or at risk) Cases or case 2 objectives To identify the source, Mode of transmission, etiological factors, To cure the patient. 3 Examination Group of people or community Individual case 4 Concern with Sick and healthy Sick 5 Diagnosis By survey, research Individual test done. 6 Where to go? Experts goes to community Patient goes to hospital 7 Area concern Mainly concern to preventive and promotive through intervention Mainly in curative field 8 Concept Bio-statistical Bio-medical 9 Presentation of result By tables, charts and diagrams By laboratory and others reports 10 Time Long process Short time sometimes long time 11 outcome Planning, implementation and health promotion Cured or disability or death