Lecture 1 Introduction of Epidemiology PDF

INTRODUCTION TO EPIDEMIOLOGY Dr. MAJDI M. SABAHELZAIN B.Pharm, MPH Learning Objectives  After studying this lesson you will be able to:  Define epidemiology  Name some of the key uses of epidemiology  Identify the core epidemiology functions  Describe research areas using epidemiolog...

INTRODUCTION TO EPIDEMIOLOGY Dr. MAJDI M. SABAHELZAIN B.Pharm, MPH Learning Objectives  After studying this lesson you will be able to:  Define epidemiology  Name some of the key uses of epidemiology  Identify the core epidemiology functions  Describe research areas using epidemiology  List the key features and uses of descriptive epidemiology  List the key features and uses of analytic epidemiology Overview  Epidemiology is the study of how disease is distributed in populations and the factors that influence or determine this distribution. Causes of death in USA in 1900 and 2009 THE OBJECTIVES OF EPIDEMIOLOGY  First, to identify the etiology or cause of a disease and the relevant risk factors.  Second, to determine the extent of disease found in the community.  Third, to study the natural history and prognosis of disease.  Fourth, to evaluate both existing and newly developed preventive and therapeutic measures and modes of health care delivery. Fifth, to provide the foundation for developing public policy relating to environmental problems, genetic issues, and other considerations regarding disease prevention and health promotion. Epidemiology and Prevention Two Approaches to Prevention: A Different View 1 The population-based approach, a preventive measure is widely applied to an entire population. 2 To target a high-risk group with the preventive measure. Definition of Epidemiology EPIDEMIOLOGY Definition of Epidemiology  The word epidemiology comes from the Greek words epi, meaning on or upon,  demos, meaning people, and  logos, meaning the study of.  In other words, the word epidemiology has its roots in the study of what befalls a population.  Many definitions have been proposed, but the following definition captures the underlying principles and public health spirit 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  Key terms in this definition reflect some of the important principles of epidemiology:  Study  Distribution frequency and pattern Determinants Health-related states or events Specified populations Application Distribution  Frequency of disease occurrence may vary from one population group to another.  Pattern means frequency by person, place and time.  Example: Hypertension more common among young black men than among young white men. Measures of Disease Frequency  Prevalence Proportion of people with a disease at any point of time or period of time.  Incidence The number of new cases in a defined population over a defined period of time. Examples of Determinants  Agents (Causes of diseases) Biologic agents--bacteria Chemical agents--carcinogens  Risk Factor Something that increases person’s chance of getting a disease. Risk Factor are often described as Modifiable ( E. g Envirmental exposures and behaviors) or Fixed  Protective Factor: Something that reduce the person’s chance of getting a disease. Eg: vegetable intake are protective against coronary heart Disease. Population  Epidemiology examines disease occurrence among population groups, not individuals.  The epidemiologic description indicates variation by age groups, time, geographic location, and other variables. Health related Events Health related Events  Epidemiology investigates many different kinds of health outcomes: Infectious diseases Chronic diseases Disability, injury, limitation of activity Mortality Active life expectancy Mental illness, suicide, drug addiction  Summary Epidemiology is the study (scientific, systematic, data- driven) of the distribution (frequency, pattern) and determinants (causes, risk factors) of health-related states and events (not just diseases) in specified populations (patient is community, individuals viewed collectively), and the application of (since epidemiology is a discipline within public health) this study to the control of health problems. USES of Epidemiology Uses  Assessing the community’s health  What are the actual and potential health problems in the  community?  Where are they occurring?  Which populations are at increased risk?  Which problems have declined over time?  Which ones are increasing or have the potential to increase?  How do these patterns relate to the level and distribution of public health services available?  Making individual decisions  When persons decide to:  e.g: quit smoking,  climb the stairs  eat a salad or  use a condom  1950s  1970s  1980s  Making individual decisions eg: Quit smoking, Climb stairs, eat salad instead of burger, Use Condoms. 1950s Cancer and Smoking 1970s Exercise and Diet = Heart Diseases 1980s HIV and Sexual behaviors  Completing the clinical picture Epidemiologists and Outbreaks eg: SARS coronavirus  Searching for causes # Causes, Risk Factors, Protective Factors (Fruits) # Causal Relationships Area for research in epidemiology  Clinical Epidemiology  Infectious disease epidemiolgy  Chronic Diseases Epidemiology  Pharmacoepidemiology  Nutritional Epidemiology  Injury and Accidents Epidemiology Core Epidemiologic Functions Core Epidemiologic Functions  Public health surveillance Surveillance is the ongoing, systematic collection, analysis, interpretation, and dissemination of health data to help guide public health decision making and action.  Notification eg: Reports about Mortality and Morbidity, Immunization Coverage Surveillance Cycle  Field investigation Surveillance (Collect Data) lead to Investigation (by Phone or Field) Objective= confirm eg: STIs= interviews to investigate other cases (Partners) eg: E.Coli= other sources of transmission Uses  Assessing the community’s health Public Health Officials responsiblefor Policy, implementation and evaluation ( Descriptive Data, Person, Time and Place) eg: SHHS  What are the actual and potential health problems in the  community?  Where are they occurring?  Which populations are at increased risk?  Which problems have declined over time?  Which ones are increasing or have the potential to  increase?  How do these patterns relate to the level and distribution of  public health services available?  Analytic studies # Surveillance and Field investigation ( Descriptive) # Causes and risk factors  Evaluation  Evaluation is the process of determining, as systematically and objectively as possible, the relevance, effectiveness, efficiency, and impact of activities with respect to established goals  Evalauions During all the operation process (Plan, Operation and impact)  eg: Immunization Program  Linkages Epidemiologist work with other in teamwork and sometimes Team Leaders (Outbreaks)  Policy development ‘‘ … and application of this study to control of health problem’’ Academic Epidemiologists vs Public Health Epidemiologists The Epidemiologic Approach The Epidemiologic Approach Counts cases or health events, and describes them in term 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 Descriptive Epidemiology Descriptive Epidemiology  The 5W’s of descriptive epidemiology: What = health issue of concern Who = person Where = place When = time Why/how = causes, risk factors, modes of transmission Time  Secular (long-term) trends  Seasonality  Day of week and time of day  Epidemic period Figure 1.5 Number of Intussusception Reports After the Rhesus Rotavirus Vaccine-tetravalent (RRV-TV) by Vaccination Date–United States, September 1998-December 1999 Cases of Salmonella Enteriditis in Chicago, February 13-21, by Date and Time of Symptom Onset  Place Urban/ Rural State, Regional or Global  Person “Person” attributes include age, sex, ethnicity/ race, and socioeconomic status. Figure 1.13a Pertussis by 5-Year Age Groups Figure 1.13b Pertussis by