progress test ( lectures 14-22) Flashcards
what is population health?
the health outcomes of a group of individuals including the distribution of such outcomes wihthin the group.
how is health distributed in NZ?
there are two important patterns
-ethinicity
-socioeconomic status
how is socioeconomic status measured?
takes into consideration factors such as occupation, income and education.
measured through deprivation the NZDep scales
how is NZDep measured?
area based measurement of deprivation, areas of 100-200 people (suburbs). given a decile score based on your deprivation. 10= most deprived, 1= least
what determines health?
general socioeconomic, cultural and envrionmental conditions
living and working conditons
social and community influences
individual lifestyle factors
age,sex and hereditary factors
what is a DALY and what does it measure?
a integrated measure of health loss. it is the sum of years of life lost and years lived with disability . One DALY represents the loss of one year of life lived in full health.
why has the DALY rate decreased by the total number of DALYS increased?
the rate has increased due to a reduction in early deaths, have the ability to keep people living longer.
The total number of DALY’s is increasing because of nz growing and aging population which sees an increase in years of poor health and disability,
demographic transition vs epidemiological transition
demographic= changes in population death and birth rates over time, growth and change in population over time
epidemiological= changes in population disease patterns over time non & communicable diseases
How has demographic transition changed over time
birthrate= decreased, more babies are surviving so people are having less
deathrate= decreased, people are living longer with less diseased better healthcare etc
total population= increased, the median age of the population is also increasing.
how has epidemiological transition changed with time?
communicable disease has decreased due to better hygiene, nutrition etc .
non communicable disease= increased
what is disease prevalence and why do we measure it
the proportion of a population who have the disease at a point in time
helps to show the burden of disease and where resources may need to be allocated within a population
how to calculate prevalence
number of people with the disease at a given point of time/ the total number of people in the population at that point in time.
what are the limitations of prevalance?
difficult to asses the development of the disease
the duration of the disease influences its prevalence (eg longer disease higher prevalence)
how to calculate incidence proportion
number of people who develop the disease in a specified period/ number of people at risk of developing the disease at the start of the period
how to calculate incidence rate?
number of people who develop the disease in a specified period/ number of person years at risk of developing the disease
when is it important to enforce age standardisation
when age structures differ and the disease risk varyies by age
what is a cross-sectional study and what can it measure?
measures exposures and/or outcomes at one point in time
eg census
it measures the prevalence
what are 4 limitations of cross sectional studies
1) cannot determine temporal sequencing- dont know whether the exposure or the outcome came first (chicken and the egg)
2) measures prevalence not incidence
3) not good for studying rare outcomes or exposures- may find very few of what you are looking for therefore not an accurate representation
4) not good for assesing variable and transient exposures or outcomes
what are some benefits of a cross sectional study
you can assess multiple exposures and outcomes
can be less expensive
relatively quick
depending on your question, good when you have stable exposures and outcomes and it can generate a hypothesis
what is an ecological study and how do you typically identify one?
You compare exposures and outcomes across groups not individuals.
usually compare countries or larger areas.
what are 2 limitations of ecological studies?
1) ecological fallacy- you cant desrcibe individual charactaristics within the group, everything catagorised on the group as a whole.
2)cant control for confounding- when there are other factors which could impact the relationship.
what are some benefits of ecological studies?
data is often routinely collected for the populations so it may be relatively easy to do and inexpensive.
what does PECOT stand for
Population
Exposure
Comparison
Outcome
Time
source vs sample population
source is the population that you are recruiting from for the study
sample is the people from the population who are actually in the study
what is a cohort study?
individuals are defined on the basis of presence or absence of exposure to a suspected risk factor
measures exposures and outcomes. see whether people are exposed to a risk factor, follow them up over time and see if they develop what you are interested in
what is vital for collecting your sample population in a cohort study
the sample population must not already have the outcome of interest.
what can you calculate from cohort studies?
incidence proportion/rate
relative risk
risk difference
what are three things you have to consider carefully for cohort studies?
1) ideally have a random selection independent of exposure status
2) can you be sure that the sample population does not already have the outcome
3) have particpants been correctly classified into exposed or comparison group.
4) follow up time, have they changed exposure status over time, has everyone been followed up over the entire study, how long do particpants need to be followed up (how long would the exposure take to develop)
what are the 4 strengths of cohort studies?
- can determine a temporal sequence between exposure and outcome
- can examine multiple outcomes from an exposure
- can calculate incidence
- good for rare exposures
what are some limitations for cohort studies?
- loss to follow up, can lead to bias
-potential for misclassfification of exposures and outcomes - not good for rare outcomes
-time consuming and expensive
how does a historical cohort study differ from a typical cohort study?
A historical study starts at the outcome.
you see who ends up with the outcome then trace back to look at whether they were exposed or not.
observational vs intervention studies
observational studies we dont go in and change things we just observe them, and dont change their exposure status.
intervention we may give exposures etc to certain groups
what is a case control study and what does it measure?
you identify people with the outcome, then you find people without the outcome and you compare their exposure likelihood leading up to that.
This allows you to calculate odds.
what is the main logic of case-control studies?
Is the exposure associated with the outcome?
what do odds ratios tell us ?
how many times as likely cases are to have the exposure compared to the controls
strengths of case control studies
can asses multiple exposure, can determine temporal sequencing, can look at rare outcomes and transient exposures, quick and inexpensive
limitations of case control studies
can only study one outcome, difficult to select people into the appropriate control group, potential selection and recall bias
what is a randomised control trial and what does it measure
testing effects of treatments/ interventions on participants randomly allocated to groups. you always have a comparison/ control group. looking to see whether the intervention increases or decreases the risk of the outcome. You can measure incidence
what is concealment of allocation and why is it important
the way that individuals are allocated needs to be concealed and unpredictable , because this ensures there isnt any bias.
what are three potential sources of bias?
- blinding
- loss to follow up (death, people moving away)
-non adhearance (people not doing what theyre supposed to in terms of getting the intervention etc)
what are three ways you can protect randomisation
- large numbers in the study
-concealment of allocation
-intention to treat analysis
what does NEAC stand for and what are they
National ethics advisory committee, the new zealand ethics committee that has established different principles to ensure that acceptable research is being carried out.
beneficence vs non-malefiecence
beneficence is the duty we have to help people where as non maleficence is the duty we have to not intentionally harm people.
what is the basic idea of clinical equipoise
the idea that the participant should not suffer any substantial disadvantage from being in the study
