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18 Cards in this Set
- Front
- Back
- 3rd side (hint)
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How can measuring the incidence of a disease help us?
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1. decide whether an epidemic is in progress 2. monitor effect of prevention programmes 3. identify potential hazard danger.
What type of diseases is incidence important for? |
'Diseases' of very short duration e.g. stroke. The focus is on events.
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What does the incidence of a disease not give us information about?
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the burden of disease. also important to know about the number of existing cases to know extent of need for particular health services.
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What is the best measure of the population at risk?
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multiplication of no. of people observed and the no. of years of observation. What is this called?
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person-time at risk/no. of person-years (p-y)
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what calculation gives the incidence rate?
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incidence rate = no. of new cases/no. of person-years (no. of persons at risk in a specified time interval).
What is this a measure of? |
individual risk - how many cases per year, per head of population
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what is the mortality rate?
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special case of incidence, where death is measured instead of disease onset.
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How would you calculate the (point) prevalence?
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no. of sufferers/no. at risk
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What affects prevalence of a disease?
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death, recovery, incidence
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What is the calculation for prevalence when incidence rate and rate of recovery & death are constant?
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P = I x L (approx. equal to)
I: incidence rate L: mean duration of disease |
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What is an incidence rate ratio (IRR) used for?
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compare incidence rates in 2 groups. rateA/rateB - if >1, what does this suggest?
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group A is at higher risk than group B
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if the mortality rate ratio comparing patients on a new treatment with those on existing treatment is <1, what does this mean?
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Suggests the new treatment is associated with a reduced risk of death.
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What is a confounding variable?
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an extraneous variable that correlates (positively or negatively) with both the dependent variable and the independent variable.
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What does indirect standardisation produce?
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a ratio of the observed events to the expected from some comparator in a single population
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what does direct standardisation produce?
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a rate which can be compared with other rates standardised in the same way.
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What is the standardised mortality ratio (SMR)?
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a summary figure describing the mortality experience of a local population compared with a standard reference population, which takes into account the confounding influences of age & sex.
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The standardised morbidity ratio is used for disease events rather than death.
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How do you calculate SMR?
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SMR = (observed deaths/expected deaths) x100
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What 4 bits of info do we need to measure disease?
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1 definition of a case
2 no. of cases (numerator) 3 size of at risk pop. (denominator) 4 time period |
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How would you calculate the ratio (relative risk) of disease?
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measure in exposed group/measure in unexposed group
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What are the 3 types of relative measures of exposure effect?
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rate, risk & odds ratio. When do they yield similar estimates of relative risk?
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When diseases are rare
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