INTRODUCTION TO EPIDEMIOLOGY.ppt

INTRODUCTION TO EPIDEMIOLOGY DR E.O. AMU DEPT OF COMMUNITY MEDICINE EKSU, ADO-EKITI OUTLINE Learning objectives Definition of Epidemiology Key issues in the definition Historical Perspectives General Principles Uses of epidemiology Epidemiologic approach Learning Objectives  After this...

INTRODUCTION TO EPIDEMIOLOGY DR E.O. AMU DEPT OF COMMUNITY MEDICINE EKSU, ADO-EKITI OUTLINE Learning objectives Definition of Epidemiology Key issues in the definition Historical Perspectives General Principles Uses of epidemiology Epidemiologic approach Learning Objectives  After this lecture, you will be able to:  Define epidemiology  Identify the key words in the definition  Summarize the historical evolution of epidemiology  Name some of the key uses of epidemiology  Identify the core epidemiology functions Definition of Epidemiology  Epidemiology is 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.  This is the most encompassing definition Key issues in the Definition of Epidemiology  A Study  It is the basic science of public health  It is a quantitative scientific discipline  It is data-driven: collection, analysis, and interpretation of data.  It relies on a working knowledge of probability, statistics, and sound research methods.  It is a method of causal reasoning: developing and testing hypotheses.  It provides the foundation for directing practical and appropriate public health action based on this science and causal reasoning.  Distribution  Concerned with the frequency and pattern of health events in a population:  Frequency: no of health events in relation to the size of the population. Allows for comparison across different populations.  Pattern refers to the occurrence of health-related events by time, place, and person.  Time: annual, seasonal, weekly, daily, hourly, weekday versus weekend  Place: urban/rural, temperate/tropical home/school/workplace  Person: age, sex, marital status, and socioeconomic status  Determinants  Factors that bring about a change or make a difference in a person’s heath  Answers the questions “Why” and “How”  Consist of both causal and preventive factors  Individual: race, genetic make-up, diet, habits, immune status  Environmental: presence of disease causing agents, vectors, poor living conditions, political instability etc Objectives of epidemiology  Study the natural course of disease from onset to resolution  Determine the extent of disease in a population  Identify patterns and trends in disease occurrence  Identify the causes of disease  Evaluate the effectiveness of measures that treat and prevent disease Health related events  Any condition that has to do with people’s health  Not just communicable diseases  Diseases, disabilities, injury, contraceptive use etc Specified Population and Disease Control  Specified population Refers to a group of people with a common characteristic e.g. residence, gender, age, race, work place etc  Disease control This is accomplished through epidemiologic research and surveillance Historical Perspectives Hippocrates  Circa 400 B.C.  Attempted to explain disease occurrence from a rational rather than a supernatural viewpoint.  Wrote the essay “Airs, Waters, and Places”  Suggested that environmental and host factors influence the development of disease  John Graunt 1662  London haberdasher and councilman  Published a landmark analysis of mortality data in 1662.  First to quantify patterns of birth, death, and disease occurrence  Noted: disparities between males and females, high infant mortality urban/rural differences seasonal variations James Lind 1747  A surgeon on a ship  Debunked the idea that scurvy was hereditary or infectious in nature  Used experimental epidemiology to establish the causation of scurvy  Found that provision of citrus fruits in the diet protected against the disease James Lind 1747  A surgeon on a ship  Debunked the idea that scurvy was hereditary or infectious in nature  Used experimental epidemiology to establish the causation of scurvy  Found that provision of citrus fruits in the diet protected against the disease  William Farr 1800  Built upon Graunt’s work  Systematically collected and analyzed Britain’s mortality statistics.  Developed many of the basic practices used today in vital statistics and disease classification.  Collected, assembled and evaluated vital statistics data  Reported to responsible health authorities and the general public.  Considered the father of modern vital statistics and surveillance John Snow 1854  An anesthesiologist  Conducted studies of cholera outbreaks in London 20 years before the development of the microscope  Discovered the cause of cholera and how to prevent its recurrence.  Work illustrates the classic sequence from descriptive epidemiology to hypothesis generation to hypothesis testing (analytic epidemiology) to application.  Referred to as “father of field epidemiology.” 19th and 20th centuries  Mid-late1800s: investigation of acute infectious disease occurrence.  1930s and 1940s: extension to non infectious diseases.  World War II and thereafter: explosion in the development of research methods Application to the entire range of health-related outcomes, behaviors, knowledge and attitudes. Doll and Hill Study: linked lung cancer to smoking Framingham Study: studied cardiovascular disease and the risk factors  1960s – 1970s: eradicated naturally occurring smallpox worldwide  I980s: epidemiology extended to the studies of injuries and violence.  1990s : molecular and genetic epidemiology New infectious disease epidemiology HIV, SARS, Ebola, Lassa, Legionella, SARS Uses/Application of Epidemiology  Assessing the community’s health (Community diagnosis/assessment)  Making individual decisions  Completing the clinical picture Identifying enough other cases to characterize the spectrum and course of new illnesses. (Clinicians & epidemiologist work together to achieve this)  Searching for causes/causal factors that influence one’s risk of disease  Policy making  Evaluation of effectiveness of health programmes/interventions Epidemiologic Approach  Epidemiology relies on a systematic approach. 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  Compares these rates over time or for different groups of people. Note: before counting can be done there must be a proper case definition Searching for causes explained  A main pre-occupation of epidemiology  Enables appropriate public health action.  Though difficult to prove a causal relationship, provides enough information to support effective action. Examples Removal of the handle from the Broad St. pump – cessation of cholera 1854 withdrawal rotavirus Vaccine in 1999 – linked with increased risk of intussusception Identification of risk factors for Legionnaires pneumonia among persons attending the American Legion Convention in Philadelphia in 1976. Bacillus was identified 6 months after References  CDC textbook of Epidemiologic Principles  Epidemiology in Public Health by Ann Aschengrau and George R Seage III  History of Epidemiology by Rodolfo Sarracci