Week 12 : Introduction to Epidemiology Demography

• Epidemiology - scientific method of problem solving
• Epidemiology - disease detectives
• Epi - among
• Demos - people
• Logos - study
• Epidemiology Study on ;

  • how people get sick and die
  • who gets sick and dies
  • how to avoid getting sick
  • who gets the disease and why
• Epidemiology - studies conducted among human populations
• Epidemiologists Study on ;

  • both sick and well people
  • crucial difference (difference of sick and without)
  • with the disease
  • disease-free
• Epidemiologic Terms ;

  • Distribution - who has the problem?

  • Determinants - what influences the problem? (contributor)
• Epidemiologic Terms;

  Risk Factors - what characteristics are associated with the disease?

  • non-modifiable (not changeable) e.g. age, sex
  • modifiable (changeable) e.g. behavior
• Uses of Epidemiology ;

  • disease occurence
  • disease cause
  • factor increasing risk of disease
  • disease extent in a population (magnitude, effects)
  • natural history of disease
  • disease characteristics
  • preventive measures and policy decisions
• Issues that Epidemiology Adresses ;

  • disease
  • mortality
  • hospitalization
  • disability
  • quality of life
  • health status
• What does Epidemiology do?

  • weighs and balances
  • contrasts and compares
  • use rates : number of events/population at risk
• Epidemiology Rates

  • events (numerator) - number of people to whom something happened (i.e. they got sick, died, etc.)
  • population at risk (denominator) - all the people at risk for the event
• Epidemic

  • environment, host, agent, time
• Causes of Epidemic

  • new agent
  • change in existing agent infectivity (how the agent penetrate/replicate in the environment), pathogenicity (ability to cause a disease), virulence (property of agent)
  • change in number of susceptible (population) - who are the people affected
  • environmental changes affecting transmissions or growth of agent (e.g. crowded environment)
• Epidemiologic Triangle

  • Agent
  • Environment
  • Individual as a function of time
• Epidemiologic Triangle (Traditional)

  • Environment
  • Host
  • Time
  • Agent
• Epidemiologic Triangle (Modern)

  • Causative Factors
  • Groups of Populations
  • Time
  • Risk Factors
• Agent

  • infectious - microbes (bacteria, viruses)
  • non-infectious - risk factors (smoking, high BP, exposure to chemicals/radiation)
• Agent

  • primary agent responsible or ascertain causative factors
  • characteristics of the agent or causative factors
  • mode of transmission (ingestion, airborne, inhalation)
  • contributing factors
  • geographic patterns
• Host

  • organisms (humans, animals) exposed to harbor a disease
• Factors affecting susceptibility to disease

  • age, gender
  • race/ethnicity
  • occupation
  • immune status
  • behaviors
• Environment

  • external to the host
• Characteristics that may cause disease;

  • weather (seasonal disease)
  • population density
  • geography
  • season of the year
  • genetic effects/family history
• Time

  • duration when a person is sick, before death, or recovery
• Time

  • Incubation Period - time from infection to symptom development (infectious agent)
  • Latency Period - time from exposure to symptom development (chronic disease e.g. cancer - non-communicable)
• Mission of Epidemiology ;

  • break the triangle, completely preventing disease or control spread
  • understand what causes disease
  • determine groups likely to get disease
  • determine geographical factors conducive to disease spread
• Demography

  • mathematical & statistical study
  • size, composition, & spatial distribution
  • human populations
  • changes over time
  • 5 processes (fertility, mortality, migration, marriage, social mobility)
• Uses of Demography

  • planning, priority setting, and fund allocation
  • growth (decline) and dispersal of population in the past
  • causal relationship between population trends and social organization
  • future developments and consequences
• Describing Population Composition

  Sex Composition

  • sex ratio
  • sex structure
• Describing Population Composition

  Age Composition

  • median age
  • dependency ratio
• Describing Population Composition

  Age and Sex Composition

  • population pyramid
• Sex Composition : Sex Ratio - compares the number of males to the number of females
• Sex Composition : Sex Ratio Formula

  Sex Ratio = number of males/number of females x 100
• Sex Composition : Sex Structure - compares the sex ratio across different categories/levels of another characteristic
• Age Composition : Median Age - value which cuts-off the upper 50% and lower 50% of the ages of the population

  • used to gauge whether the population is young or old
• Age Composition : Age-Dependency Ratio - represents the number of dependents that need to be supported bu every 100 persons in the economically-active groups
• Age Dependency Ratio Formula

  Age Dependency Ratio = population 0-14 years + population >65 years / population 15-64 years old x 100
• Age & Sex Composition : Population Pyramid - a graphical presentation of the age and sex composition of the population

  • describes demographic trends of the population in the past