midterm 2 equations/calculations Flashcards
prevalence
cases / total population
cumulative incidence
new cases in a specific period of time / # of people at risk at the beginning of the period
incidence rate
of new cases during a given time / # of person time (years,months,days) contributed when people were at risk
incidence rate can also be known as..
force of morbidity or mortality, incidence density
point prevalance
the proportion of people in a population with the disease at a given point in time (ex July 8 2004)
period prevalence
the proportion of individuals in a population with the disease at any time during a specified period (ex during 2004)
use of prevalence
how many people are affected?
estimate probability an individual will have the disease during a point in time
project health care and other policy needs and issues
estimate costs associated with a particular disease
prevalence cannot tell us..
how long someone has had the disease
cause of disease
cumulative incidence should exclude… because..
people who already have the disease, people who cannot develop the disease
to avoid underestimating risk
uses of cumulative incidence..
estimate probability (avg risk) that a person will develop the disease during a specific time period
research on causes, prevention, and treatment of a disease
incidence rates shows us..
true rates - incidence rate can go up or down
denominator represents the window of time people were at risk at developing the disease, not the number of people at risk at the beginning
reported in unit of time (.. per 100 person days, … per 100 person years)
use of incidence rates
research on causes, prevention, and treatment of disease
crude mortality rates
of new deaths / average population during the year
infant mortality rates
of deaths in children up to 1 year in a specific year / # of live births in the same year
standardized incidence or mortality ratios
of deaths / # of expected standard population
proportional mortality rate
proportion of deaths from a specific cause / proportion expected for standard population
case fatality rate
of dead from disease in specific period / total number of cases
how to establish causation
temporality - exposure must come first
strength of association - strong effect?
biological plausibility - what is the likely biological mechanism?
consistency - found across a range of studies?
dose response - level and duration of exposure
sufficient cause
factor that will inevitably produce disease
component cause
factor that contributes toward disease causation but not sufficient enough to cause disease on its own
necessary cause
any agent that is required for the development of a given disease
what is considered an exposure?
infectious agents
behaviours
intrinsic characteristics of individuals
social or environmental factors
observational studies
the researcher does not intervene in any ways: measurement of occurrence of disease or health outcome, comparing patterns of expose and disease outcomes, identifying risk factors associated with heath/disease
experimental studies
investigator tries to change something and measure the effect on the disease outcome - clinical trials, preventive trials
descriptive studies
research that describes the occurrence of disease and/or exposure
remember: PERSON PLACE TIME
ask: WHO WHAT WHEN WHERE WHY
analytic studies
primary purpose is to evaluate the association between the exposure or characteristic and the development of a particular disease
WHY? HOW STRONG?
ecological studies
compare the prevalence of exposures and disease occurrence in populations
cross sectional studies
study group chosen to represent a subgroup of society/cross section of the population
case control study
choose individuals with disease or outcome of interest and a comparison group without disease
prospective cohort studies
follow up studies: follow people over time to see what happens
compare rates of occurrence of disease in people with out without a particular exposure
epidemiology (where is the word derived from? what does it mean)
epi - among
demos - the people
logia - study
= the study of what is upon the people
epidemiology dictionary definition
the study of the distribution and determinants of health-related states in specified populations, and the application of this study to control health problems
applications of epidemiology
identifying the cause of a new syndrome
assessing risk of exposure
determine whether treatment “x” is effective
identifying health service use needs and trends
identifying practical prevention strategies
endemic
cases are continually occurring in the population
epidemic
outbreak of a disease in a localized group of people - spread by: vectors, carriers, sudden intro of a new pathogen; more cases than usually expected
pandemic
epidemics that have spread beyond their local region and are affecting people in various/all parts of the world
how many people fell ill from TB? (2016)
10.4 million people
how many people died from TB? (2016)
1.8 million people including 400,000 with HIV and TB
sensitivity
how well does the test classify people with disease as diseased? a/(a+c)
specificity
how well does the test classify people without the disease as none diseased? d/(b+d)
applications of epidemiology
identifying the cause of a new syndrome
assessing risk of exposure
determining whether treatment “x” is effective
identifying health service needs and trends
identifying practical preventions strategies
ottawa health promotion strategies
build healthy public policy
create supportive environments
strengthen community action
develop personal skills
reorient health systems
bradford hill criteria
temporality - exposure must come first
strength of association - strong effect?
biological plausibility - what is biological mechanism
consistency - is it found across a range of studies
dose response - level and duration of exposure
