Public health

• Epidemiology


  The study among people of health problems, illnesses, diseases, of epidemics, risk factors, relationships of above and other factors, relationship with time and with dose, effectiveness of interventions
• Public health


  The science and art of preventing disease, prolonging life and promoting health through the organized efforts and informed choices of society, organizations, public and private, communities and individuals
• Concepts of epidemiology


  • Observational studies
  • Interventional studies
• Concepts in basic epidemiology

  • Concepts of population, time, exposure to factors (risk and protective and others), illness, diseases, health problems, health related issues
  • Existence in populations of factors that affect health-risk factors, correlates
  • Risk factors: biological, environmental, social, behavioural, economic, personal characteristics such as personality, attitudes, values
• Epidemiology


  The study of the distribution, determinants and frequency of health problems in populations
• Epidemiology


  The study of the distribution and determinants of disease frequency in man
• Epidemiological approach


  1. Asking questions

  2. Making comparisons
• The 5W's of descriptive epidemiology

  • What? - health issue of concern: case definition
  • Who? - person
  • Where? - place
  • When? - time
  • Why/how? - causes, risk factors, modes of transmission
• Changes can occur over a long period of time - secular trends
• Dengue fever is related to rainfall patterns
• Person


  • Age
  • Sex
  • Ethnic variability
  • Socio economic status
• Risk factor


  An attribute or an exposure that is significantly associated with development of a disease
• For many diseases, the 'agent' is still unidentified, for example in coronary heart disease, cancer, peptic ulcer, mental illness
• Examples of risk factors


  • Smoking
  • Hypertension
  • Elevation of serum lipids
  • Obesity
  • Lack of exercise
  • Stress
  • Family history
  • Alcohol
  • Chemicals
  • Ionizing radiation (x-ray, gamma rays)
  • Certain viruses
  • Environmental pollution
• High risk groups


  Groups of people who are at a higher risk of developing a disease or a behavior because of presence of certain characteristics or factors
• Uses of epidemiology


  • Study the 'causes' or determinants
  • Apply principles and methods epidemiology in epidemiological study designs (observational, analytical, experimental or interventional)
  • Studying health problems in any setting (schools, hospitals, work places, estates, communities)
  • Investigating disease: new outbreaks, epidemics
  • Surveillance
  • Identifying risk factors
  • Evaluation of effectiveness of interventions (vaccines, drugs, educational programmes, food fortifications etc.)
• Epidemiology


  The study of the distribution and determinants of health related states and events in populations and the application of this study to control of health problems
• Last JM: A Dictionary of Epidemiology 4th Ed. 2001
• Distribution


  • Includes frequency and pattern
  • Frequency: the number of health events (e.g. number of cases of diabetes in a population), also the relationship of that number to the size of the population
  • Pattern: the occurrence of health-related events by time, place, and person
• Time patterns


  • annual
  • seasonal
  • weekly
  • daily
  • hourly
  • weekday versus weekend
• Place patterns


  • geographic variation
  • urban/rural differences
  • location of work sites or schools
• Personal characteristics


  • demographic factors (age, sex, marital status, and socioeconomic status)
  • behaviors
  • environmental exposures
• Determinants


  Causes and other factors that influence the occurrence of disease and other health-related events
• Illness does not occur randomly in a population, but happens only when the right accumulation of risk factors or determinants exists in an individual
• Two broad types of epidemiology


  • Examining the distribution of a disease in a population, and observing the basic features of its distribution in terms of time, place, and person
  • Testing a specific hypothesis about the relationship of a disease to a putative cause, by conducting an epidemiologic study that relates the exposure of interest to the disease of interest
• Analytic epidemiology


  Typical study designs: cohort, case-control
• Research


  A process of systematic inquiry that entails collection of data; documentation of critical information; and analysis and interpretation of that data/information, in accordance with suitable methodologies set by specific professional fields and academic disciplines
• Study design


  A specific plan or protocol for conducting the study, which allows the investigator to translate the conceptual hypothesis into an operational one
• Epidemiological studies


  • Experimental
  • Observational
• Experimental studies


  • Randomized Controlled Trials
  • Quasi Experimental
• Observational studies


  • Descriptive
  • Analytical
• Descriptive study designs


  • Case series
  • Case reports
  • Ecological studies
  • Cross sectional
• Descriptive studies describe occurrence of outcome
• Analytic studies describe association between exposure and outcome
• Basic question in analytic epidemiology

  Are exposure and disease linked?
• Steps in conducting a descriptive study


  • Defining the population
  • Defining disease under study
  • Describing the disease
  • Measurement of disease
  • Compare
  • Formulate hypothesis
• Cross-sectional (prevalence) studies


  A cross-sectional study provides information about a health condition / disease that exists at a given time/during a given period
• Cross-sectional studies cannot specify a direction
• Case study


  A detailed description of disease occurrence in a single person. Unusual features of the case may suggest a new hypothesis about the causes or mechanisms of disease
• Case series


  Clinical case-series: usually a coherent and consecutive set of cases of a disease (or similar problem) which derive from either the practice of one or more health care professionals or a defined health care setting, e.g. a hospital or family practice