week 5 lecture 1: epidemiology 1

• what is epidemiology?

  the study of the incidence, distribution, and control of diseases
• what is epidemiology sometimes referred to as?

  the 'pathology of populations'
• what is prevalence?

  an epidemiological measure of how commonly a disease or condition occurs in a population
• prevalence measures how much of some disease or condition there is in a population at a particular point in time
• prevalence is calculated by dividing the number of people with a particular disease by the number of individuals examined
• in what format is prevalence normally given?

  decimal
• what is incidence?

  a measure of the rate of occurrence of new cases of a disease
• how is incidence calculated?

  by dividing the number of new cases in a specified time period by the size of the population (under consideration) who are initially disease-free
• incidence is normally considered in terms of 'per 100,000 people'
• what is a risk factor?

  a measurable factor which, when applied to an appropriate, statistically defined group of people, leads to an increase in the presentation of a disease in that population
• give an example of a risk factor

  smoking, for lung cancer
• give 4 components of measuring disease frequency

  1. deciding what constitutes a case of disease in a study
  2. defining the period of time of risk of disease
  3. obtaining permission to study people
  4. relating cases to population and time at risk
• what is an endemic?

  a constantly present disease/condition in a given ecology
• what is an epidemic?

  a sudden widespread outbreak of disease
• what were Graunt's epidemiological observations?

  1. excess of male births
  2. high infant mortality
  3. seasonal variations of mortality
• define infant mortality rate

  deaths of infants under one year of age, per 1,000 live births
• what kind of indicator is infant mortality rate?

  widely used and sensitive indicator of socio-economically related health of populations
• how does infant mortality rate change over time?

  it decreases as the population grows
• infant mortality rate varies between countries, but is used as an index of a country's development stage
• infant mortality rate is a useful measure in developed countries
• what are the 2 'broad' types of epidemiology?

  1. descriptive
  2. analytic
• what does descriptive epidemiology do?

  examine the distribution of a disease in a population, and observing the basic features of its distribution in terms of time, place, and person
• what is the typical study design associated with descriptive epidemiology?

  community health survey
• what is a synonym for a descriptive study?

  cross-sectional study
• what is a case-series study?

  a qualitative study that tracks subjects with a similar diagnosis, similar known exposure, or undergoing similar treatment
• what is a case-series study also known as?

  a clinical study
• what are 2 advantages of case-series studies?

  1. quicker
  2. cheaper
• what can be applied to a case-series study (advantageous)?

  retrospective
• what is a disadvantage of a clinical study?

  it does not give any indication of the absolute risk of a factor
• who determined the link between contamination and disease in Broad Street, London, and when?

  John Snow in 1854
• what did John Snow trace in 1854?

  he traced a source of cholera to a contaminated hand pump in Broad Street
• how did John Snow locate the hand pump responsible for the cholera outbreak?

  using a spot map
• cholera was not accepted as having an oral-faecal route, so government officials reattached the hand pump after the major outbreak had dissipated
• what is a cross-sectional study?

  a descriptive method where one set of data is collected at the same time as other data
• what do cross-sectional studies allow for?

  trends to be investigated, and correlations to be made
• what is the aim of analytic epidemiology?

  to test a specific hypothesis about the relationship of a disease to a putative cause, by conducting an epidemiological study relating the exposure of interest to the disease of interest
• what are 2 typical study designs used in analytic epidemiology?

  1. cohorts
  2. case-control studies
• what does putative mean?

  supposed
• what is a cohort?

  a group of people with a shared characteristic
• give an example of a historical cohort study

  study performed on the children of tubercular and non-tubercular patients; this happened in Germany in 1913