L1- Measuring Disease Frequency Flashcards
Epidemiology
study of distribution and determinants of disease frequency in human populations and the application of this study to control diseases and factors that contribute to disease
ratio- general
dividing one quanity by another
example - % of woman that have oral cancer / % of men who have oral cancer
proportion - general
type of ration where numerator is subset of the denominator
example - N men who have oral cancer / N men in population
(numerator is also part of denominator)
rate - general
type of proportion where denominator includes a unit of time (1 day – several years)
prevalence - definition
the number of people in the population who have a disease by the total number of people in the population
*proportion of the population affected by the disease at a given time
example - # of people with a disease/ total # people in the populaiton
what does prevelance tell us and its value?
tells us HOW MUCH but not why or how
useful for assessing the burden of disease in a population
NOT accurate measure of disease RISK
NOT USEFUL for how it was caused
ranges from 0-1 and can be a %
Incidence
frequency of NEW cases during a SPAN OF TIME in people “at risk”
focus is on measuring the probability of DEVELOPING disease during a defined span of time
example - # new cases during specified time interval / total population “at risk”
proportion of the population newly affected by the disease during a given time period
Range > or equal to 0
more accurate than prevelance for exploring properties and determinants of disease
cumulative incidence
N of new cases of disease between date a and b / n in populatoin at risk at beginning of study period
relative risk
tells us how many times higher or lower the disease risk is among the exposed as compared to the unexposed group
gives info on strength of association
fixed population
membership is permanent and defined by and even
examples - atomic bomb survivors
millennials
dynamic population
membershipe is transient and defined by being in or out of state
- residents of the city of boston
- flu patient
point prevelance
proportion that has a disease ata specific point in time and the focus is on EXISTING disease - not development of new cases
what can the point be in point prevelance?
specific calander time or a a lifetime event like birth, death, at entry into military
period prevelance
poroprtion of a population that has disease during a given time period and the focus in on EXISTING disease during that peiod of time, not development of new cases - but includes cases at the beginning of period and ones that occured during
what does incidence focus on?
probability of DEVELOPING disease during a defined span of time
