Lecture 2 Flashcards
(20 cards)
What is a case definition?
A set of criteria is used to decide whether someone has a particular disease or other health condition. Different case definitions can give VERY different pictures
When is the Attack Rate commonly used
Used for acute, infectious diseases that occur in well-defined outbreaks over a short period of time (e.g, foodborne illness outbreaks, influenza outbreaks)
What would chronic diseases typically be measured with?
Usually measured with prevelance (# of cases in a population @ a given time) and Incidence (new cases over a time in a population (how is this growing or decreasing over time))
What does prevalence tell us?
Tells us what proportion of a pop has the disease at a specific point in time. Usually reported as a %.
Prevalence = # of ppl with disease @ given point in time / Total # of ppl in pop @ same time
What does Incidence tell us?
Measures new cases of the disease over time in the population that is AT RISK. Shown as the infection rate that reflects the # of new cases per year.
What does the epidemiologist bathtub help us understand?
The picture helps us understand how quickly people recover (evaporation), die (the drain), get sick (the tap), and are sick /prevalence/ (the tub)
Direct Standardization, what is it & how is it used
DS involves calculating the overall rate that you would have expected to find in each of the populations(e.g countries) had they all had the same age structure as a ‘standard’ population.
Must know 1 the age-specific rates in your study populations, and 2 the age distribution of a standard pop
What are the ADV and DISADV of Direct Standardisation?
Good for comparing large populations where age-specific rates are reliable, less good for small pops.
All rates are standardized to the same age distribution allowing direct comparison between different populations
What is is period prevelance?
Measures the proportion of the population that HAD disease @ a certain point in time. Complex because measures combined prevalence (everyone who had disease @ the start period) & Incidence (all new cases during period)
What is the Incidence?
How quickly ppl are developing new cases (only new cases)
Incidence Rate measures what?
A true rate because it include a measure of time eg, per year
IR = #ppl who develop disease in year/ average # ppl in pop in same year
p~IRxD is what
Prevalence= Incident rate x average Duration of disease
What is the Incident proportion
Tells us the population of ‘at risk’ of developing the disease who actually became ill & developed disease during time period. Also the probability of average risk that an individual will develop the disease during time period.
How is a standardized mortality Ratio acquired?
SMR is calculated by dividing # of deaths/ expected #
What is the proportional mortality ratio
Measure the relative importance of a particular cause of death. PMR looks like an SMR but is used when insufficient information to calculate an SMR
What is the case fatality ratio
CRF -> proportion of ppl given a disease or condition who die from it within a period of time. If a disease occurs or takes a long time to kill (cancer) survival rate is more appropriate.
Survival Rate
Conditions such as cancer, and mortality is exposed in SR. Proportion of patients still alive after a # of years after disease
Life expectancy is what
Mortality-based measure that accounts for the timing of death.
How is Life expectancy calcualted?
Using a “Life Table”. Total # years of expected life for entire cohort added up; life expectancy @ birth is total divided by 100,000
What are the potential years of life lost?
Measures life but to what is being lost. Sometimes described as a health gap measure. PYLL is taken from the expected age value or predefined age
