Introduction to Epidemiology PDF

Principles of Epidemiology and FHSC 282 Biostatistics 1  Punctuality Students are expected to be on time for class Attendance Rules and Students are required to attend class...

Principles of Epidemiology and FHSC 282 Biostatistics 1  Punctuality Students are expected to be on time for class Attendance Rules and Students are required to attend class Participation is also accounted for Regulations Plagiarism No plagiarism is allowed (Zero tolerance) If caught cheating, the student will be reported to the disciplinary committee 2  Exercises Different practice sessions will take place through out the course Some of the solutions will be posted on Moodle, the rest will be done and corrected in class Rules and Calculators It is the students’ responsibility to bring his/her own Regulations calculator to class. cont’d Syllabus THE SYLLABUS IS UPLOADED ON MOODLE FOR ALL CAMPUSES PLEASE REFER TO THE SYLLABUS TO KNOW THE DATES AND TIMES OF YOUR QUIZZES AND EXAMS, AS WELL AS THE GRADING SCHEME 3 Rules and Regulations Cont’d Communication All communication between the instructor and the student is done through the balamand email The student is responsible for activating and checking his email frequently Books All books pertaining to the course are on reserve in the library, you are highly encouraged to consult them Some exercises and their solutions are available in the book, please refer to them while studying 4  By the end of this lecture, students will learn about: Etymology Learning History of Epidemiology objectives Definition of Epidemiology Objectives of Epidemiology Achievements of Epidemiology 5 Etymology Epidemiology Epi Demos Logos Upon, among People Study The study of what is upon the people 6  Public health is a set of collective actions that aim to improve populations health… Epidemiology as a public Epidemiology is a health quantitative discipline discipline… of public health 7  MOST PEOPLE DON’T KNOW WHAT EPIDEMIOLOGY IS, ALTHOUGH IT USUALLY MAKES THE HEADLINES 8 Epidemiologic research addresses many contemporary health-related problems For example Risks associated with smoking Prevention of youth violence Factors associated with obesity and substance abuse Recent epidemics (e.g. Ebola virus hemorrhagic fever, Zika virus disease) 9  Clinical Medicine Epidemiology Individuals Populations Diagnosis and Prevention and Treatment Control What’s the link What is wrong with What are the leading between this patient? causes of death or medicine & What treatment is disability in this population? epidemiology? appropriate? What can be done to reduce / prevent them? 10  In the practice of medicine, a doctor looks at the patient’s history and health issues They are so Epidemiology on the other hand, when it is applied, it looks at health problems encountered in the different yet clinical setting interlinked… The interplay of both disciplines have led to the development of what is now known as clinical epidemiology Epidemiology serves as a strong support to preventive and clinical 11 medicine  The study of: ▪ distribution ▪ and determinants of health-related states or events (including disease) in specified Definition of populations, “Epidemiology” ▪ and the application of this study ▪ to the control of diseases and other health problems. 12 The study of: distribution and determinants of health-related states or events (including disease) in specified populations, and the application of this study to the control of diseases and other health problems. Epidemiology is a quantitative discipline, often referred to as the basic science of public health. It relies on concepts of probability and biostatistics. 13 The study of: distribution and determinants of health-related states or events (including disease) in specified populations, and the application of this study to the control of diseases and other health problems. Where? Who, When? Descriptive epidemiology: Describes patterns and frequency of health outcomes in the population. Patterns: occurrence by characteristics of time, place, person. “When, Where, Who?” Frequency: number, rate or risk of health outcome in the population 14 The study of: distribution and determinants of health-related states or events (including disease) in specified populations, and the application of this study to the control of diseases and other health problems. What? Why? How? Analytical epidemiology Factors or variables that influence the occurrence of diseases or health events. 15 The study of: distribution and determinants of health-related states or events (including disease) in specified populations, and the application of this study to the control of diseases and other health problems. Epidemiology is concerned with the collective health, whereas clinicians are concerned with individuals’ health. The scope of epidemiology extended from epidemics of communicable diseases, to non communicable diseases (Injuries, birth defect, mental health, maternal and child health,…) 16 Epidemiological triad Traditional triangle based on the communicable disease model Agent is the cause of the disease, Host is the organism (human/animal) that harbors the disease, Environment is the external conditions that cause or allow disease transmission More advanced models are proposed to consider the non-communicable diseases 17 The study of: distribution and determinants of health-related states or events (including disease) in specified populations, and the application of this study to the control of diseases and other health problems. Epidemiology provides foundation for public health actions, guides public health activities. Three levels of control: Primary, secondary, tertiary 18  Levels of prevention: I- Primary: prevention of a disease before it occurs. Example: health promotion, health education programs, immunization Levels of control II-Secondary: during early phase of diseases, includes activities that limit disease progression or impairment/disability III-Tertiary: at later stages of disease by providing rehabilitations to limit or block progression of disability 19 Population Distribution Determinants focus Control of Outcomes Quantification health problems Key Characteristics of Epidemiology 20  History of Epidemiology 21 Evil eye…witchcraft Terrifying occurrences 22 History of Epidemiology Fifth century B.C.: Hippocrates suggested that the development of a human disease might be related to the external and personal environment of an individual. Explaining disease occurrence from a rational point of view instead of a supernatural one 23 History of Epidemiology London, 17th century: John Graunt ▪ Published the analysis of weekly counts of births and deaths in London ▪ Quantified patterns of outcomes in the population (noting birth, death occurrence, male-female disparities, high infant mortality, urban-rural differences, and seasonal variations) Graunt highlighted the need for routinely collected data in providing information about human illnesses 24 History of Epidemiology London, 19th century: William Farr ▪ Founder of routinely collection of data (refer to surveillance system in lec 2) ▪ Used a categorization system for the causes of death antecedent of the modern “International classification of diseases” (refer to lec 2) ▪ Examined possible linkage between mortality rates and population density (defined as number of persons per square mile) 25 History of Epidemiology Broad Street, London, had a major cholera outbreak in 1849. Two different water companies supplied water from the Thames River to houses in the same area. In 1852, the Lambeth Company relocated its sources of water to a less polluted portion of the river. Snow noted that during a later cholera outbreak in 1854, those residents served by the Lambeth Company had fewer cases of cholera than residents served by the other water company (Southwark and Vauxhall Company). 26 He then used a “spot map” to mark the distribution of households with cholera deaths with respect to water pump locations. 27 Snow gathered information on where persons with cholera had obtained their water. Consumption of water from the Broad Street pump was the one common factor among the cholera cases. The handle of the pump was later removed Simple preventive public health measure to control the outbreak 28  Snow had noted that districts DEATHS with the highest mortalities had DEATHS WATER NUMBER OF FROM water supplied by two PER 10.000 SUPPLY HOUSES CHOLERA companies HOUSES 1853-1854 Southwark & 40,046 1,263 31,5 Snow collected data on the Vauxhall water supply company and the occurrence of cholera death Lambeth 26,107 98 3,7 from around 300.000 houses Both 256,423 1,422 5,9 companies 29  Application of epidemiologic methods Used mapping (spot maps of cases) John Snow’s Contribution Used data tables to describe infectious disease outbreaks s Recommended a public health measure to prevent disease 30  Describe health Identify priority Determine status of health burden of populations programs diseases Epidemiology Confirm and Guide health Evaluate public investigate authorities, health allows us to: outbreaks direct resources interventions Evaluate Identify disease medical determinants treatments 31 Uses of epidemiology Confirm outbreak by reviewing historical data Conduct specimen and data collection to investigate outbreak and find etiology Identify mode of transmission, human/animal reservoir Develop guidelines for prevention programs 32  To identify etiology of diseases Conduct epidemiological studies to explore the association between exposure factors and health outcomes Identify risk factors and protective factors Evaluate associations and causality Uses of To evaluate medical treatments epidemiolog Evaluate new drugs/treatments y Evaluate different dosages of same drug Assess new programs for screening and early detection 33  Achievements of Epidemiology 34 Achievements of Epidemiology: Smallpox eradication In the late 18th century, 400.000 people died from smallpox each year and 1/3 of survivors became blind. “Variolation” resulted in deaths, infection of other individuals with smallpox, or development of other infections. 35 Achievements of Epidemiology: Smallpox eradication Edward Jenner (1749-1823): Vaccine development: He took material from lesions on the arm of a dairy maid who had an active case of cowpox and injected it into the arm of an 8-years-old boy. The boy was later inoculated with smallpox but did not develop the disease Jenner concluded that the vaccine was effective and vaccinated other kids, including his own son Painting of the first vaccination, “vacca” 36 Achievements of Epidemiology: Smallpox eradication The results of the first vaccination and what followed saved millions of people around the world from deaths and disability due to smallpox. During efforts conducted in 20 years, 350 million new cases had been prevented. In 1980, the World Health Organization certified eradication of smallpox. 37 Other examples of epidemiology applications: Methyl mercury poisoning In April 1956, an epidemic of an unknown disease of the central nervous system were noticed. By October 1956, 40 patients had been discovered, 14 of whom had died. First cases were thought to be infectious meningitis. Mercury compounds were released with water from a factory in Minamata, from 1932 till 1968. 38  Survey of affected and unaffected people: victims were mainly fishers, or whose main diet consisted of fish. Other examples of Minamata disease: first documented environmental epidemiology disease applications: As of March 2001, 2265 victims has been officially recognized, of whom 1784 had died. Methyl mercury poisoning Over 10,000 had received financial compensation. http://www.soshisha.org/english/10tishiki_e/10chisiki_3_e.pdf 39  HOW HEALTH PROBLEMS CHANGE OVER TIME 1839: Cholera was the major 2013: Cuba fights to contain cholera cause of death in England after a century without the disease NBC News, 19 Jan 2013 40 How health problems change over time Example from Lebanon Distribution of measles cases by week of rash, Lebanon, 2003-2006, and 2013, up to 1st January 2014 41 ‫ وزارة اﻟﺻﺣﺔ اﻟﻌﺎﻣﺔ‬/ ‫اﻟﺟﻣﮭورﯾﺔ اﻟﻠﺑﻧﺎﻧﯾﺔ‬ Determine burden of diseases 42 http://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736%2812%2961766-8.pdf  A shift in the pattern of morbidity and mortality from: EPIDEMIOLOGIC Infectious to non-infectious diseases (chronic and degenerative diseases) TRANSITION: Resurgence of infectious diseases CHANGING PATTERN OF Along with the demographic transition, and countries DISEASES development: Changing lifestyle Nutrition Improved sanitation Globalization Improved access to health services Increasing awareness 43  Epidemiological transition 44  Epidemiologic transition: Changing pattern of diseases Chief causes of death in the US, 1900 Chief causes of death in the US, 2005 Ran Cause of death % of total Ran Cause of death % of total k mortality k mortality 1 Pneumonia and 1 Heart disease 26.3% 13.1% influenza 2 Cancer 23.0% 2 Tuberculosis 12.6% 3 Cerebrovascular 5.8% 3 Diarrhea, enteritis and disease ulceration of the 9.2% 4 Chronic lower intestines 5.4% respiratory disease 4 Heart disease 8.9% 5 Accidents 4.8% 5 Intracranial lesions of 6 Diabetes 6.9% 3.1% vascular origin 7 Alzheimer disease 2.9% 6 Nephritis 5.7% 8 Pneumonia and 7 Accidents 4.7% 2.5% influenza 8 Cancer 4.1% 45  One world..one health What are the areas of research in epidemiology? 46 Implications of Epidemiologic transition : Modern Epidemiology Sub-disciplines Modern epidemiology has branched into different sub-disciplines: Outcome-oriented epidemiology Chronic disease epidemiology Cardiovascular disease epidemiology Cancer epidemiology Diabetes epidemiology Infectious disease epidemiology AIDS epidemiology Injury epidemiology Exposure-oriented epidemiology Environmental epidemiology Occupational epidemiology Nutritional epidemiology Genetic epidemiology 47  Epidemiology is a quantitative discipline of public health that provides the basic foundation for any public health decision Key notes Epidemiology: Determining health status of population and guiding control activities Descriptive epidemiology: describe diseases patterns and frequency Analytical epidemiology: looks for diseases determinants using statistical concepts Need to have routinely collected information on health: William Farr founder of routine collection of data John Snow: father of field epidemiology and outbreak investigation Epidemiological transition with the demographic transition Statistical skills are needed while applying epidemiology 48