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14 Cards in this Set
- Front
- Back
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Attack Rate
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# ppl at risk in whom a certain illness develops / total number of people at risk
* useful for comparing the risk of disease in groups with different exposures |
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Incidence
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# new cases of disease occurring in the pop'n during a specified period of time / # people at risk of developing the disease during that periodof time
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Cumulative Incidence
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# new cases of disease in pop'n at risk during a specified period of time / # people at risk for developing the disease at BEGINNING of time period
* estimates the risk of a new outcome in a given time period * proportion |
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Incidence Density
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* # new cases of disease in pop'n at risk during a specified period of time / person-years at risk for disease
* person-years: sum of the different times that each individual was at risk * rate |
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Prevalence
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# cases WITH DISEASE in a pop'n at a specific time / total pop'n at that time
* snapshot of presence of disease (existing + new cases) in a pop'n at a given time * measures the burden of disease in a community * not a measure of risk |
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Point Prevalence
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prevalence of a disease at a point in time
ex. "Do you currently have asthma?" |
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Period Prevalence
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prevalence of a disease during a certain period
every person in the numerator had the disease at some time during the period specified - not concerned with when disease developed or how long it persisted ex. "Have you had asthma during the last 5 years?" |
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Relationship between Incidence and Prevalence
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Prevalence = Incidence x Duration
* duration is determined by death or treatment |
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Increasing and Decreasing Prevalence
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Increase:
- addition of new cases (incidence) - new measure that enhances survival or better detects the disease Decrease: - cures & deaths (reduce # of diseased ppl in pop'n) |
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Examples of Prevalence = Incidence * Duration
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1) rapid cure or death
- prevalence ≈ incidence - short duration 2) chronic disease (diabetes) - ↑ prevalence - long duration & low incidence 3) Acute, short duration disease (strep throat) - ↑ prevalence and ↓ incidence |
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Annual Mortality Rate
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total # deaths from all causes in one year / # persons in the pop'n at midyear
* anyone in the denominator must be able to enter the numerator - denominator include those who have the disease and those who don't have it but are at risk * be mindful that popn's can differ in regard to many characteristics that affect mortality |
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Specific Rate
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placing a restriction on both the numerator and the denominator
Ex. age-specifc mortality rate # deaths from all causes in one year in children younger than 10 years old / # children in the pop'n younger than 10 years old at midyear Ex. cause-specific rate # deaths from lung cancer in one year / # persons in the pop'n at midyear |
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Case-Fatality Rate
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# individuals dying during a specified period of time after disease onset or diagnosis / # individuals with the specified disease
denominator limited to those who already have the disease * what PERCENTAGE of people diagnosed with a certain disease die within a certain time after diagnosis * measure of the severity of the disease |
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Proportionate Mortality
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# deaths from disease X in the U.S. in 1999 / total # deaths in the U.S. in 1999
* what PROPORTION from all deaths was caused by disease X * does not tell us the risk of dying from a disease |
