Standardisation (mortality)

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Mortality rates

  • Deaths per year divided by estimate of people alive during that year.
  • Usually per 10,000
  • Crude mortality rate, vs eg
  • Cause-specific mortality rate
  • Age-adjusted standardised mortality rate
  • Age-/gender-/ethnicity-specific mortality rate

Crude mortality rate

  • Very easy to calculate
  • Deaths per 10,000 popn per year
  • Useful in crises as crude measure
  • >1/10,000 per year is an emergency
  • Rates of about 3 observed in Dafur

Standardisation

  • Standardisation is used to remove the effect of [an] unwanted variable[s] such as age and/or sex from a comparison between two populations.small numbers
  • Methods of comparing study population with wider population
  • Means of judging external validity
  • Direct standardisation is used whenever stratum-specific rates are available
  • Indirect standardisation is used when stratum-specific rates are unavailable or unstable because of

Direct standardisation

  • Calculate the age-specific rates for study population.
  • Take number of people in those age groups in standard population, and calculate the rate that would apply to that population, if the age-specific rates in the study population applied.
  • Gives a RATE.

Indirect standardisation

  • Take the number of deaths in the study population.
  • Take the age-specific rates for the standard population, and calculate the number of deaths that would be expected in the study population if the standard rates applied (by multiplying the standard rates by the number of people in age group in the study population)
  • Divide the actual rates by the expected rates, and multiply by 100.
  • Gives a RATIO.