Introduction To Epidemiology

Introduction to Epidemiology Dr. Bashier Eltayeb Ahmed MBBS, MCM 1  The term “epidemiology” is derived from the Greek word (meaning epidemic). epi: upon demos: people logos: thought The study (thinking) of what happens to people...

Introduction to Epidemiology Dr. Bashier Eltayeb Ahmed MBBS, MCM 1  The term “epidemiology” is derived from the Greek word (meaning epidemic). epi: upon demos: people logos: thought The study (thinking) of what happens to people 2  Definition of Epidemiology: Anderson (1930): The science of disease occurrence Mac Mahon et al (1970): The study of the distribution and determinants of disease prevalence in man 3  Definition of Epidemiology “The study of the distribution & determinants of health-related states or events in a specified population, and the application of this study to the control of health problems” Dictionary of Epidemiology (Last 1988) 4  Definition of Epidemiology: Epidemiology is the science of applied, practice oriented research, intended to advance the general knowledge base for community and clinical medicine (Adapted from Miettinen OS, 2007) 5  Definition of Epidemiology Epidemiology: “The 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 health problems”. (Last 1988) 2/13/2023 6  Definition of Epidemiology: Study includes: surveillance, observation, hypothesis testing, analytic research and experiments. Distribution refers to analysis of: times, persons, places and classes of people affected. 7  Definition of Epidemiology: Determinants include factors that influence health: biological, chemical, physical, social, cultural, economic, genetic and behavioural. Health-related states and events refer to: diseases, causes of death, behaviours such as use of tobacco, positive health states, reactions to preventive regimes and provision and use of health services. 8  Definition of Epidemiology: Specified populations include those with identifiable characteristics, such as occupational groups. Application to prevention and control the aims of public health—to promote, protect, and restore health. 9  Definition of Epidemiology Distribution is concerned with:  Pattern & frequency of health events in a population Pattern refers to: the occurrence of health- related events by time, place and person characteristics. Frequency refers to measurement of frequency of health-related events(disease disability or death) and summarizing this information in the form of rates and ratios. Descriptive Epidemiology 2/13/2023 10  Definition of Epidemiology Determinants Epidemiological methods are used as tools to search for causes & other factors that influence the occurrence of health related Analytic Epidemiology 2/13/2023 11  Definition of Epidemiology Health-related states or events include: - communicable diseases - non-communicable diseases - injuries, birth defects - maternal-child health - occupational & environmental health - behaviors related to health (exercise, seat-belt use etc.) 2/13/2023 12 Definition of Epidemiology can be further elaborated as follows  Three inter-related components 1. Frequency Quantify existence or occurrence of disease Prerequisite to investigate patterns of disease occurrence 2. Distribution Descriptive epidemiology (person, place and time) Formulate hypotheses for causal and preventive factors 14  Three inter-related components 3. Determinants Derived from the above two Allows testing hypotheses 15  Aims of Epidemiology: 1.to describe patterns of health and disease within populations 2.to interpret these differences 3.to apply our results to public health practice, and 4.to evaluate the effect of health-related interventions  Ultimate Aims of Epidemiology: 1. To eliminate or reduce the health problems of community. 2. To promote the health and well-being of society as a whole.  Scopes of Epidemiology 1. Causation of the disease. 2. Natural history of the disease. 3. Health status of the population. 4. Evaluation of Interventions.  Historical background 2/13/2023 19  THE ROOTS OF EPIDEMIOLOGY DEVELOPMENT 1915 – till to date GROWTH 1600-1905 ORIGIN (HIPPOCRATIC TIMES ) 463 BC  ORIGIN 2400 YEARS AGO HIPPOCRATES planted the seed & the tree of epidemiology has taken its roots in 463 BC Described the distribution of diseases by season, age, climate and personal behavior William Farr – Father of Vital Statistics Collected & analysed Britain’s morbidity & mortality statistics. Examined effects of marital status, occupation, etc on morbidity & mortality statistics John Snow- Father of Modern Epidemiology Identified mode of transmission Incubation times Cause & effect Clinical observations of cholera  Doll & Hill (1947) Studied effect of smoking among a cohort of English doctors Well designed epidemiological study Demonstrated cause (smoking) and effect (lung cancer) The process of development IT HAS GROWN FROM PURE OBSERVATIONS FROM HIPPOCRATES TO &ADVICES COUNTING OF CASES WILLIAM FARR &ANALYSIS NATURAL Studies BY JOHN SNOW Well designed epidemiological BY DOLL & HILL & OTHER study EPIDEMIOLOGISTS IN THE LAST TWO CENTURIES  SCOPE OF EPIDEMIOLOGY The scope have widened & changed over time Started of as a study of epidemics Till mid 19th century epidemiology was only a study of epidemics Then it became study of infectious diseases, later extended to study of non-infectious diseases Now has become a discipline that is beyond study of a diseases.  IMPORTANCE OF EPIDEMIOLOGY CLINICAL MEDICINE – Its knowledge is important to the clinician in making diagnosis, treatment and prognosis – Clinician requires background clinical epidemiological information about a ds i.e incidence rates, sex and age distribution…all these info points to the likely diagnosis while at the same time excluding unlikely diagnosis  IMPORTANCE OF EPIDEMIOLOGY PUBLIC HEALTH Epidemiology is the cornerstone of Public Health It contributed to eradication and control of communicable diseases & to prevention of non communicable diseases Achievements : control of infectious diseases –smallpox and childhood infection by mass immunization, effective screening for breast and cervical cancer  Applications of epidemiology in public health 1. Preventing disease and promoting health. 2. Community health assessment (Community Diagnosis) and priority setting. 3. Improving diagnosis, treatment and prognosis of clinical diseases. 4. Evaluating health interventions and programs.  Epidemiological approach: 1) Asking questions. 2) Making Comparisons.  1. Asking questions Asking questions and getting answers leading to further questions:- 1- Related to health events. 2- Related to health action  1. Asking questions Related to Health Events 1. What is the event? (Problem) 2. What is magnitude? 3. Where did happen? 4. When did happen? 5. Who are affected? 6. Why did it happen?  1. Asking questions Related to Health Action 1. What can be done to reduce the problem? 2. How can be prevented in future? 3. What action should be taken by community? 4. What resources required? 5. How activities to be organized? 6. What difficulties may arise?  2.Making Comparisons: Basic approach in epidemiology is making comparison and draw inferences. E.g. making comparison between two groups one having the disease and the other not having the disease. Or making comparison between individuals. Compare study group to contrast group. The Epidemiologic approach In very simple terms, the epidemiologist: Counts cases or health events, and describes them in terms of time, place, and person; Divides the number of cases by an appropriate denominator to calculate rates; and Compares these rates over time or for different groups of people.