Week 11 : Basic Concepts and Principles of Epidemiology

• Epidemiology - study of factors that determine the occurence and distribution of disease in a population
• Epi - upon
• Demos - population
• Logos - study
• Epidemiologists - deal with data from group of patients or even entire population
• Classical Epidemiology

  • studies the distribution and determinants of disease in populations and the community origina of health problems
  • interested in discovering risk factor that might be altered in a population to prevent or delay disease, injury, and death
• Clinical Epidemiology

  • application of principles of epidemiology to clinical medicine
  • clinical epidemiologists often study patients in health-care settings rather than in the community at large
• Etiology - cause or origin of a disease or abnormal condition
• Natural History - way a disease progresses in the absence of medical or public health intervention
• Predisease - before the disease process begins

  Primary Prevention - preventing the disease process from starting
• Latent - disease process has already begun but is still asymptomatic

  Secondary Prevention - screening for the disease and providing appropriate treatment that may prevent progression to symptomatic disease
• Symptomatic - disease manifestations are evident

  Tertiary Prevention - disease manifestations are evident intervention may slow, arrest, or reverse the progression of disease
• Agent

  • what of the triangle
  • whatever causes the disease

  four categories ;

  • biologic agents
  • chemical agents
  • physical agents
  • social and psychologic stressors
• Host

  • who of the triangle
  • the person or organism harboring the disease
  • resistance is influenced by; genotype, nutritional status, body mass index, immune system and behaviour
• Environment

  • where of the triangle
  • external factors that causes or allow disease transmission
• Vectors

  • how of the triangle
  • serves as vehicles to transmit disease
  • include insects, arachnids, and mammals
  • to be an effective transmitter of disease, the vector must have a specific relationship to the agent, the environment, and the host
• BEINGs Model - serve as mnemonic device for the major categories of risk factors for disease

  • Biologic factors and Behavioral factors
  • Environmental factors
  • Immunologic factors
  • Nutritional factors
  • Genetic factors
  • Services, Social factors, and Spiritual factors
• Vaccination

  • herd immunity/population immunity - protects the immunized individual, but also prevents that person from transmitting the disease to others
  • indirect protection - from an infectious disease that happens when a population is immune either through vaccination or immunity developed through previous infection
• Solution of Public Health Problems

  • vaccination
  • improved sanitation
  • vector control
  • erection of large river dams
• Epidemiological Principles and methods are applied in

  • clinical research
  • disease prevention
  • health promotion
  • health protection
  • health services research
• ultimate aim of epidemiology aims and objectives of epidemiology

  • to eliminate or reduce the health problems of community
  • to promote the health and well-being of society as a whole
• Distribution

  • time, place, person
  • pattern - hypothesis for causative/risk factor = etiological hypothesis
  • descriptive epidemiology
• Determinants

  • causes, risk factors, mode of transmission
  • how and why of disease
  • identifying the causes and risk factors for diseases
  • testing the hypothesis - biostatistics
  • analytical epidemiology
• Scope of Epidemiology

  • causation of the disease
  • natural history of the disease
  • health status of the population
  • evaluation of interventions
• Applications of Epidemiology in Public Health

  • preventing the diseasw and promoting health
  • community health assessment (community diagnosis) and priority setting
  • improving diagnosis, treatment, and prognosis of clinical diseases
  • evaluating health interventions and programs
• Public Health - refers to collective actions to improve population health
• Epidemiology - one of the tools for improving public health, is used in several ways
• Epidemiology

  • unit of study - defined population or population at risk
  • concerned with the disease pattern in entire population
  • concerned with both sick and healthy

  Clinical Medicine

  • unit of study - case
  • physician is concerned with the disease in the individual patient
• Epidemiology

  • epidemiologist is confronted with the relevant data derived from the particular epidemiological study (community diagnosis)
  • seek to identify the source of infection, mode of transmission, and an etiological factor to determine the future trends, prevention, and control measure

  Clinical Medicine

  • physician seeks to diagnosis for which he derives prognosis and prescribes specific treatment
• Epidemiology

  • epidemiologists goes to the community to find out the disease pattern and suspected causal factors in the question

  Clinical Medicine

  • patient comes to the doctor
• Epidemiological Approach

  • asking questions
  • making comparisons
• 5 W’s

  • case definition - what
  • person - who
  • place - where
  • time - when
  • causes - why
• Making Comparisons

  • find out the differences in the agents, host, and environment conditions between two groups
  • weighs, balances, and contrasts give clues to etiological hypothesis