deck_159697 Flashcards
What are the two different interpreations of the question “how much disease is there,” and why are they useful to know?
a) the number of new cases that occurred -focuses on NEW EVENTS-useful when monitoring pandemicsb)The number of people affected by the disease-counts PEOPLE with EXISTING DISEASE-describes burden of disease-useful as a measure of need for services
Define incidence, providing the associated equation
IncidenceMeasuring rate of new casesEx. 300 heart attacks in 50,000 dye workers over 1.5 yearsIncidence rate = new events/person x time (years) = events per persons per year
Define prevalence and why is not considered a rate?
Prevalence Measuring existing casesPrevalence is a proportion NOT a rateDenominator is PERSONS not PERSONS per time
What is the realtionship between prevalence and incidence?
Prevalence = Incidence x Length of Disease
What is systematic variation in rates of disease?
The differing levels of non-random risk which exist between different groups of people
How is Systematic variation helpful in understanding aeitology of disease?
Compare levels of exposure in two groups of people and identify causal factor for a disease. Having identified causal factor, possible to prevent exposure and thus decrease incidence
How can you compare incidence rates between different groups, and why is it useful
Compare incidence rates via Incidence Rate Ratio (IRR) RateB(exposed)/RateA(unexposed)If incidence rate in group B higher than rate in group A, implies difference exposure was associated with the difference in rates of disease
How can systematic variation be used to determine efficacy of treatment?
Incident Rate Ratio usedExposure is treatment A (old treatment) or B (new treatment) Mortality rate ratio = RateB/RateA
What is rate a measure of?
Absolute risk
What is ratio a measure of?
Relative risk
Why could systematic variation be considered a nuisance?
Confounding factors such as age and sex, which are non modifiable and strong determinants of health, are variants but not particularly useful as cannot be changed.
Why is a confounding factor a nuisance?
Confounding factors can explain ALL or Part of an apparent association between an exposure and a disease
How would you deal with confounding by age?
Could use age specific rate raitos – For instance, use age bands (20-24, 25-29)Narrow age bands, little confounding due to age occurs, so rate ratios more like to be valid
What would be the issue when using age bands?
results are difficult in interpret as too many answers (one from each age band)
What is Standardised Mortality Rate?
Indirect SMR is a summary figure comparing OBSERVED levels of mortality with EXPECTED levels of mortality if a standard reference populations age-sex specific rates were applied to the study populations age-sex groups
