14-21 lectures (progress test 2) Flashcards
what is epidemiology?
the study of the occurrence and distribution of health-related events, states or processes in specific populations
what is population health?
the health outcomes of a group of individuals including the distribution of such outcomes within a group
what does population health look at?
the big picture and the pattern of health impacts on a population
what does socioeconomic status show within population health?
as deprivation increases, so does the number of hospitalized people
what does the distribution of socioeconomic status show in NZ?
that the money rate affects the health of the Maori and Non-Maori
what are the 2 important patterns of health distribution in NZ?
ethnicity and socioeconomic
what is NZdep?
an area level of deprivation so the whole of NZ is divided into areas
each area has a different decile area and it includes everyone in NZ
what is absolute poverty?
an income level below which a minimum nutritionally adequate diet plus essential non-food requirements is not affordable
What is relative poverty?
the amount of income a person, family, or group needs to purchase a relative amount of basic necessities of life.
what identifies basic necessities?
they are identified relative to each society and economy
what is the trend between deprivation and health?
greater deprivation leads to poorer health
what are social determinants of health?
the conditions in which people are born, grow, live, work and age
what can population vary from?
a small group of people to a whole country
what can a public health model do?
-defines and measures a problem
-describes causes and consequences
-develops and evaluates interventions
-disseminates effective policy and practices
what are the 2 factors that are relative to the measure of occurrence?
prevalence
incidence
what is incidence sometimes referred to as?
cumulative incidence
what are the 2 segments that incidence is divided into?
incidence proportion
incidence rate
what is MEPTV?
Measure of occurrence
Exposure or outcome
Population
Time point
Value
what is prevalence?
the proportion of a population who have the disease at a point in time
its the existing cases within our desired population at a specific point of time
how do we calculate the prevalence?
the number of people with the disease at a given time
‘divided by’
the total number of people in the population at a given time
what do we report prevalence with?
MEPTV
what are 2 prevalence limitations?
difficult to assess the development of disease
Is influenced by the duration of the disease
what is incidence?
the occurrence of new cases of an outcome in a population in a specific period of follow-up
what is IP?
incidence proportion
what is IR?
incidence rate
what is the difference between IP and IR?
what we use as our denominator
what is incidence proportion?
the proportion of an outcome-free population that develops the outcome of interest in a specified time period
how do we calculate incidence proportion?
the number of people who develop the disease in a specified period
‘divided by’
number of people at risk of developing the disease at the start of the period
what do we need to consider in an incidence proportion?
if the people already have the condition as well as if the condition is something that they cannot develop
what are 2 limitations for incidence proportions?
-assumes a ‘closed’ population
-highly dependent on the time period
what is the incidence rate?
the rate at which new cases of the outcome of interest occurs in a population
how do we calculate the incidence rate?
number of people who develop the disease in a specified period
‘divided by’
number of person-years at risk of developing the disease
what are 3 reasons that someone might stop being at risk in an IR study?
-they become a case
-they are lost to follow-up
-follow-up time ends
how do we report IR?
we use MEPTV without the T
what are 2 limitations of the IR?
-person-time not available
-complex to calculate
what is the dumb down explanation of prevalence?
existing cases - distribution, burden
what is the dumbed-down explanation of IP?
new cases - risk
what is the dumbed-down explanation of IR?
new cases - speed
what do we need to consider when comparing populations?
-do the age structures differ?
-does the disease risk vary by age?
what is age standardisation?
the age structure differs and disease risk varies by age
what is descriptive epidemiology?
a person, place and time
also is observational
what is analytic epidemiology?
association (exposures and outcomes), causation, observational or intervention studies
what does a cross-sectional study measure?
exposures and/or outcomes at one point in time
what is a cross-sectional study used to describe?
prevalence, compare prevalence, generate hypothesis, plan
what is the GATE frame?
the population takes a sample and has exposure/comparison groups and is graphed into an outcome graph
what are some limitations of a cross-sectional study?
-it’s temporal sequencing
-measures prevalence not incidence
-not good for studying rare outcomes or exposures
-not good for assessing variable and transient exposures or outcomes
what do ecological studies do?
compare exposures and outcomes across groups not individuals
what do individual level studies do?
look at it on a single persons status
what do group level studies do?
look at groups of peoples status
what are ecological studies used for?
-compare between populations
-assess population-level factors
-consider hypothesis
what are some limitations for ecological studies?
-ecological fallacy
-cannot control for confounding
-cannot show causation
How can we describe the fundamental characteristics and logic of analytical studies?
either using PECOT or GATE frames
what is PECOT?
Population
Exposure
Comparison
Outcome
Time
where does the GATE frame start?
at the source which is a population sample
what is the source?
the population the sample is recruited from
what is the sample?
the population included in the study
what are measures of association used for?
to quantify data
what is RR stand for?
relative risk
what is relative risk?
how many times as likely is the exposed group to develop the outcome than the comparison group
how do we calculate the relative risk?
incidence exposed
‘divided by’
incidence comparison
what is risk difference?
the differences in incidences and this tells us how many extra/fewer cases of the outcome in the exposed group are attributable to the exposure
what does exposure not change?
the occurrence of the outcome
so there are no association between exposure and outcome
what is the null value?
when there is an equal occurrence in both groups so there is the same incidence of outcome
what are cohort studies?
a is individuals are defined on the basis of the presence or absence of exposure to a suspected risk factor
how do we get a cohort study?
-identify a source of the population
-recruit the sample that doesn’t have the desired outcome
-assess exposure to identify which groups participants belong in
-we follow up over time and observe whether they have developed the outcome
what type of model is a cohort study?
analytic epidemiology
what makes up the measures of occurance?
the incidence proportion and incidence rate
how to calculate the risk ratio?
IPe
‘divided by’
IPc
how to calculate the rate ratio?
IRe
‘divided by’
IRc
how to calculate the risk difference?
IRe - IRc
IPe - IPc
where does the exposed group come from in the cohort studies?
from the recruited sample
why do we have to not have the sample population does not already have the desired outcome?
because they cant later see if they develop the outcome if they already have it
where does the comparison group come from in the cohort studies?
from the general population
what do we need to make sure in cohort studies?
that participants have been correctly classified as either exposed or comparison group
why do we follow up people in cohort studies?
to see if they are still engaged and don’t become a loss of study
what are 4 strengths of cohort studies?
-determined temporal sequence between exposure and outcomes
-can examine multiple outcomes from an exposure
-can calculate incidence
-good for studying rare exposures
what are some limitations of cohort studies?
loss to follow up could lead to bias
the potential for missclassification of exposure/outcomes
they are not good for studying rare outcomes
they are also time consuming
can end up being very expensive
where do perspective cohort studies start?
at the exposure
strengths of historical studies?
less time consuming
less expensive
good for outcomes that take time to develop
where do historical cohort studies start?
at the outcomes
limitations of historical cohort studies?
they use existing data and we may not know about all the relative factors so it could lead to bias
what are 3 things that case-controlled studys give?
-overveiw of design
-measure of association
-important points
what are case controlled studys?
they identify people with outcomes and find people without outcomes.
they also compare exposures likelihood before hand (odds)
what are the 5 steps of case controlled studies?
-identify source population
-identify people with outcome (cases)
-sample population without outcome from the same population
-measure exposure prior to outcome in cases and controls
-compare odds of exposure to calculate measure of association (odds ratio)
how do we calculate odds of exposure in cases we used?
a/c
how do we calculate the odds of exposure in controls we use?
b/d
what does OR mean?
odds ratio
what does odds ration mean?
is people with outcome are x times as likely to have had the exposure than people without the outcome.
is OR and RR equal or not?
they are approximates
do controls have outcomes?
nope
what is case selection?
usually try to identify incident cases
what do case-control studies represent?
the exposure distribution of people without the outcome in a source population
they must be capable of becoming a case
what does RCTs mean?
randomised-controlled trials
what type of epidemiology are RCTs?
analytic
what does the R C T mean in an RCT?
Randomized-participants randomly allocated to groups
Controlled-there is a control (comparison) group
Trials-testing effect of treatments/interventions
why do we allocate people to random groups in RCTs?
to make the intervention and comparison group as similar as possible
this is called exchangability
what is a confounding factor?
something that is muddling up the effect we are seeing between the exposure and the outcome
it is a key threat to the validity
what does exchangeability allow us to do?
to only look at the intervention and nothing else that may effect the outcome
how do we eliminate confounding?
by randomizing
this applies to potential confounding factors (known) and unknown confounders
what do we need to be able to have a suitable RCT?
a reasonable amount of participants
what is randomisation?
the random allocation of participants either the intervention or controlled group
what is random selection?
where people from the source population are randomly selected to participate in the study
what is cluster randomisation?
this is where groups are randomized instead of individuals which is good if the intervention is better used among groups
what is intention-to-treat anylysis?
preserves the benefits of randomization
participants are analyzed in the groups that they are randomized into regardless of weather they stuck to that group
what is per-protocol?
which analyses to according to what they actually did so the benefits of randomization are lost and confounding is re-introduced
2 types of benefits within randomization?
intention-to-treat
per-protocol
what is blinding?
not knowing which participants are in the group and eliminating bias
whats a way that bias can occur in RCTs?
a loss to follow up and non-adherance
what are some strengths of RCTs?
randomisation
best way to test intervention
can calculate incidence
temporal sequence
what are limitations of RCTs?
not all exposures are appropriate to be randomly allocated
harm of intervention
what is another phrase for ‘harm of intervention’?
clinical equipoise
