Studied by 5 people
labubu <3
Define epidemiology
The study of how much dis-ease occurs in groups/populations and the factors that determine differences in dis-ease occurrence between two groups.
Define occurrence
The transition from a non-diseased state to a dis-eased state. Comparisons of dis-ease occurrence are typically called 'estimates of associations' - the term effect describes a causal relationship.
What is the benefits of measuring disease occurrence in a population
Can inform health service planners about the types of health services required for populations including health promotion and disease prevention. Measuring disease occurrence across different ethnic groups can help identify causes/predictors of disease occurrence.
Define population
Any group of people who share a specific common factor.
What do you need in order to calculate numerical variables and why?
Categorical value as you need to know how many people (and their data) to find an average
What is a correlation coefficient
The association between numerical exposures and numerical outcomes
Define incidence
The number of onsets of dis-ease out of the number of people in the study population occurring during a period of time.
Explain incidence
Most appropriate for dis-eases that have an easily observable onset. Require the disease out come to be a categorical variable, as we measure actual people/events rather than use numerical averages, allocation before outcome, longitudinal study
Explain incidence proportion
counts everyone who started in the study in the denominator and everyone who has disease onset during the study time period in numerator
Explain incidence rate
is a more exact measurement of incidence because rather than including everyone who started in the study in denominator, once a person has an event, they are removed - participants are counted in units of person-time
Define prevalence
counting the number of people with a dis-ease at one point in time and then dividing the number of people in the study group at that point in time
Explain prevalence
Used when the transition into a dis-ease is not as easily observable. Difference in prevalence between two points in time is a change in prevalence. With prevalence you have no idea what happened before taking this measurement, you just know that at this current time - this is the proportion you have therefore only make correlations and not causal relationships. Allocation and outcome happen at same time. Used with death always
What is more useful, incidence/prevalence and why?
Incidence is more useful as prevalence relies on death and cure rates, can have high rate of incidence but low prevalence if death/cure rate is high. Incidence doesn't rely on death/cure rates as just counting the number of onsets of dis-ease
Define period prevalence
The proportion of people who become dis-eased over a period of time, measured at one point in time, defining an onset is crucial, doesn't include the number of episodes an individual has had note that period prevalence has a backwards diagonal arrow and not the average horizontal arrow that prevalence has
How would you explain (in words) RR
"risk in one (specified) group is (e.g. 2 times higher) than in another (specified) group"
RR
Relative risk or ratio of occurrences, EGO/CGO no effect line is at RR=1
How would you explain (in words) RD
"the amount of extra disease attributable to a particular risk factor in the exposed group"
RD
Risk difference, difference in occurrence, attributable risk n.b. different from PAR, no effect value =0 ARI,ARR (absolute ......)
Recruitment error
Non-response recruitment error: Often only a small proportion of the population agrees to participate in a study. If the non-responders are different from the responders this can cause significant recruitment error
External Validity Error: When the study findings aren't representative of the wider population. In some studies it is not necessary to recruit participants who are representative to determine if a particular type of antibiotics works
Allocation error
Confounding error: If EG and CG differ in ways apart from the study 'exposure', and if these other differences also have an effect on the study outcome, then it's not possible to know whether the actual study exposure or the other factors caused EGO and CGO to differ (these other factors are called confounders). Reduced by stratified analysis.
Allocation measurement error: Inaccurate measures of exposures are usually known as measurement errors but as they can result in participants being allocated to the wrong EG or CG, we shall consider it a type of allocation error.
Adjustment: has a baseline measurement been done and adjustments been made if necessary?
Maintenance error
Contamination/switch groups: participants do not maintain their exposure and comparison groups status throughout the study - don't comply
Co intervention: are exposed to other factors that could influence the study outcome. Best way to reduce this is double blinding
Drop out of the study/loss to follow up
Compliance: always take their prescribed drug etc
Blind objective measurements
Outcome measurement error: Instrument error (e.g. sphygmomanometer adding 3mm/Hg to every reading) or deficiencies with measurement methods
Single/double/triple blinding improves outcome allocation when the measurement is not very objective (e.g. doctor judging a patient based on previous prejudice notions about that persons' cultures typical behavior, and so doesn't diagnose them with as much care and concern as the doctor feels they'll just end up back in hospital)
Use objective measurements where possible (e.g. blood tests instead of questionnaires
Analysis errors
Has a baseline measurement been done and adjustment been made?
Baseline measurement: gathering information about EG and CG, and seeing how similar the groups are to each other and to the whole population
Stratified analysis: adjusts for confounding caused by allocating more of one group of people to exposure group rather than comparison - disease is calculated for each strata
random sampling error
Every representative sample recruited will be slightly different from each other sample just by chance. Reduced by increasing the samples size.
random allocation error
the EG and CG in a RCT may differ by chance alone particularly if the trial is small. Reduced by a larger sample size
random measurement error
Our ability to measure biological factors in exactly the same way each time is poor. Caused by random allocation error
Explain a 95% CI
'there is about a 95% chance that the true value in the whole population lies within the 95% confidence interval'
Describe the relationship between sample size, random error and width of CI
Larger sample size, reduces random error, and therefore reduces width of the C.I.
When there is no overlap between the CIs of EGO and CGO....
it is reasonable to assume that EGO and CGO are reasonably different from each other, rather than due solely to random error. The C.I. for RR and RD will not cross the no effect line.'
When there is overlap between the CIs of EGO and CGO....
there is too much random error to determine if there is a real difference between EGO and CGO.
What does p<0.05 mean
Given the null hypothesis is true, the chance of getting the result purely by chance is less than 5% when p<0.05
Define systematic review
Recruiting a group of studies addressing the same question however a systematic review is only valid if the studies included in the review are also valid.
Define meta analysis
Combining the results of a number of systematic reviews to reach a final value. Creates a summary estimate of effect which if it does not cross no effect line then suggests there is likely to e.g. have a real treatment benefit.
Combining multiple similar studies in a meta analysis is the same as what
Same as conducting a big study
What are meta analysis mainly used for
meta analyses are used mainly to combine RCTs that individually have too much random error to demonstrate whether or not the intervention has a real effect.
Describe an RCT
Longitudinal study (incidence,) experimental study, equivalizes groups by random allocation
What is the main purpose of an RCT
Tests effects of interventions
What are the strengths and weaknesses of RCT
Strengths: Reduces confounding as equivalizes groups
Weaknesses: maintenence error, logistical and ethical limitations, costly
Describe a cohort study
Longitudinal study (incidence,) can have prevalence measures, observational study, allocation via measurement (based on previous exposures)
What is the main purpose of a cohort study
Measures the effects of exposures/risk factors
What are the strengths and weaknesses of a cohort study
Strengths: can view multiple outcomes at same time, no recall bias, reverse causality error, ethical
Weaknesses: bad for rare outcomes, confounding, maintenance error,
Describe a cross sectional study
Prevalence (Cross sectional,) observational study, allocation(exposure) and outcome are measured at the same time
What is the main purpose of a cross sectional study
To determine the burden of disease on a population at a given time
What are the strengths and weaknesses of a cross sectional study
Strengths: no maintenance error, cheap, repeatable
Weaknesses: bad for rare outcomes, correlations not causations, confounding, unreliability in answer
Describe an ecological study
Incidence/prevalence, observational/experimental
What is the main purpose of an ecological study
Establishes trends and causes
What are the strengths and weaknesses of ecological studies
Strengths: cheap, quick, good for rare outcomes
Weaknesses: confounding
What are the steps for age standardisation
Crude death rates, age specific death rates, age standardize
What is one assumption in age standardisation
Disease is defined in the same way in both populations
Define determinant of health
any event, characteristic or other definable entity, that bring about a change for the better or worse in health.
What is primary, secondary and tertiary care
Tertiary care: hospital based care e.g. rehabilitation
Secondary care: referred to by primary healthcare providers like specialist care e.g. neurologist, dermatologist
Primary care: patients regular/first source of health care e.g. GP setting, pharmacist, physiotherapist, community based
What is the Bradford Hill criteria used for
Used to determine causality - aid, don't need to fulfil all criteria to prove causality
List all of the Bradford Hill criteria
Temporality: the exposure must come before the dis-ease, essential to establish a causal relation
Strength of association: the stronger an association, the more likely it is to be causal in absence of known biases (selection, information and confounding) although a weak association does not rule out causality
Consistency: replication of findings but different investigators at different times, in different settings with different methods (multiple studies show similar results)
Biological gradient (dose-response): incremental change in disease rates in conjunction with corresponding changes in exposure
Biological plausibility of association: biologically, does association make sense?
Specificity of association (single weakest): a single cause leads to a single effect or an effect has a single cause - diseases have multiple interacting causes and many outcomes share causes
Reversibility: the demonstration that under controlled conditions changing the exposure causes a change in outcome << no exposure = no outcome
Define component, necessary and sufficient cause of rothmans causal pie
Component cause: one of many factors that contributes towards dis-ease causation, but is not sufficient to cause dis-ease on its own
Necessary cause: factor that must be present if a specific dis-ease is to occur
Sufficient cause: factor that will inevitably produce a specific dis-ease - adequately cause dis-ease on its own
Explain level one of the Dahlgren and Whitehead mode
Individual lifestyle factors
Non-modifiable (innermost circle)
Habitus - the lifestyle, values, dispositions and expectations of particular social groups learned though everyday activities. Ability to change behaviors may vary by social groups.
Genes are important but so too is the influence of the environment. Single gene disorders=rare among the population, polygenic inheritance=influences likelihood of offspring developing a disease
The choices you make as an individual impact on the likelihood that you will have a good/bad health
Define habitus
the lifestyle, values, dispositions and expectations of particular social groups learned though everyday activities. Ability to change behaviors may vary by social groups.
Explain level two of the Dahlgren and Whitehead mode
Level TWO: Social and Community, and Living and working conditions
Modifiable - families and friends play a significant role in developing normative behaviours and attitudes and behaviours of people living and working in the local community influence the sense of what is normal and acceptable
Social Capital - Networks of relationships in society that allow it to function effectively. i.e. not WHAT you know, but WHO you know. Provides an inclusive environment for people from diverse backgrounds
Explain level three of the Dahlgren and Whitehead model
Level THREE: Socioeconomic, cultural and environmental conditions and Living and working conditions
Physical - water quality, clean air
Built - Design of communities: buildings, roads, light rail
Cultural - Knowledge, beliefs and values accepted by a group of people
Biological - (Re-)emerging toxins affecting populations
Ecosystem - biodiversity, climate change, the ecological footprint
Political - Approaches to improving population health
Define upstream and downstream interventions
Upstream: operate at the macro level, such as government politics and international trade agreements
Downstream: operate at the micro level, such as treatment systems, and disease management
Define agency
the capacity of an individual to act independently and make free choices. More downstream.
Define structure
social, physical and environmental conditions/patterns that influence a person's choices and opportunities available. More upstream.
Define micro, meso and macro level
Micro level - individual
Meso - family, living, work
Macro - national/global
Define proximal determinants
a determinant of health that is proximate or near to the change in health status. 'Near' refers to any determinant that is readily and directly associated with the change in health status
Define distal determinants
Distal determinants: a determinant of health that is either distant in time and/or place from the change in health status, also referred to as 'upstream factors' e.g. national, political and legal factors
What group of people have benefitted the most from health promotion programmes in NZ
Dominant cultural populations e.g. non Maori
Describe Te Pae Mahutonga
A set of guidelines for Maori specific health promotion that is divided into 4 key tasks (Mauriora, Waiora, Toiora and Te Oragna) and 2 key prerequisites (Nga Manukura and Te Mana Whakahaere.) Is not specific to Maori Health so can be used in mainstream promotion as well.
Describe Mauriora
A sense of cultural identity and access to the Maori world (Te Ao Maori - access to Marae, Te Reo, Maori ecological resources.) Improving their sense of cultural identity increases empowerment that Ottawa Charter dictates.
Describe Waiora and Toiora
Waiora: environmental protection to allow preservation of spiritual connection the individuals have with nature. Physical environments are a key determinant of health so they made sure they have clean air, water, smoke free environments, safe bed sharing
Toiora: healthy lifestyle e.g. don't smoke, advocating breast feeding, safe sex, diet
Describe Te Oranga
Participating and engaging in society, individually and collectively (social determinants of health - ensuring they have the resources in place to enable them to have access to good health) and increasing their ability, capacity and willingness to access good health services available which is determined by SEP.
Describe Nga Manukura
effective leadership (health and community leadership) in the community in terms of cultural and professionals and working with these leaders in collaboration to provide the maximum possible effect
Describe Te Mana Whakahaere
autonomy, capacity for self governance and community control and enabling political environment - enabled communities to engage with themselves
What are the problems with conventional western health promotion
Based on Western models of healthcare - different cultural dynamics
relies on universal formula for health - does not consider the differing values and beliefs held by Maori people therefore less relevant
Often simply adapted for Maori and therefore doesn't incorporate Maori values and realities into design of health promotions
What are examples that shows Maori health inequities
Life expectancy at birth for Maori is less than non Maori, distribution of almost all illness is greater in Maori populations, Maori are disproportionally deprived (NZDep 2013,) living deciles of Maori are usually worse than non Maori. Ethnic inequalities in health are fundamentally driven by the unequal distribution of health risks and opportunities (social determinants) - Maori are over represented in child poverty and in other measures of socioeconomic deprivation
What focus does prevention, promotion and protection have
Disease prevention: disease and risk factor focused
Health promotion: wellbeing focused
Health protection: environmental hazard focused
Describe the 3 levels prevention can exist in
Primary prevention: reduces exposure of RF and aims to prevent the disease from occurring in first place. Is defined as any intervention that lowers incidence. Secondary prevention: preventing the more serious consequences of the disease that individuals already have from getting worse, palliative care.
Tertiary prevention: reduce the progress of complications of established disease, limiting disease progression or providing better rehabilitation to enhance quality of life in the longer term.
What can primary prevention be split into
High risk and population strategies
Explain the 3 basic strategies for health promotion
ENABLE: to provide opportunities for all individuals to make healthy choices through access to information, life skills and supportive environments (INDIVIDUAL LEVEL STRATEGY)
ADVOCATE: to create favourable political, economic, social, cultural and physical environments by promoting/advocating for health and focusing on achieving equity in health (SYSTEMS LEVEL STRATEGY)
MEDIATE: to facilitate/bring together individuals, groups and parties with opposing interests to work together/come to a compromise for the promotion of health (STRATEGY THAT JOINS INDIVIDUALS, GROUPS AND SYSTEMS)
Describe what the Alma Atta is and explain it
Alma Atta 1978 is prerequisites for good health, advocated a health promotional approach to primary care, protect and promote the health of all (SPESFIE)
S-shelter
P-peace and safety from violence in community
E-good education
S-social justice (peace and safety - feel safe)
F-food
I-income and economic support (supporting the people that actually need it)
E-stable ecosystem and sustainable resources
Describe what the Ottawa Charter is and explain the 5 priority action areas using SCEPH
Ottawa Charter is guidelines on how to make promotional strategies
S-develop personal skills - improving health education, make informed decisions e.g. awareness campaigns
C-strengthen community action - empower groups to make their own decisions e.g. self help groups
E-create supportive environments - maintaining natural resources e.g. water and sanitation programmes
P-build healthy public health policies - pre charter has GP focus, charter changed primary health care model and included health promotion in model e.g. taxation on alcohol and cigarettes
H-re orientate health services towards primary level healthcare - promoted the need for health for all policies e.g. not just in health sector but in road environment e.g. health education services
What does the Ottawa Charter acknowledge
Health is a fundamental right for everybody (human right lens,) that is requires both individual and collective responsibility, the opportunity to have good health should be equally available and good health is an essential element of social and economic development.
Explain screening
Involves identifying unrecognized diseases/risk factors for disease by applying tests to the entire population on a large scale (primary or secondary level of prevention and it can be on a population/HR level basis.) Purpose is to take someone that doesn't know if they have disease and dividing an already asymptomatic population into those who are likely/unlikely to have disease
What determines the reliability of the "likely/unlikely" in screening
Sensitivity and specificity
Explain the levels of screening
Primary level screening: screening for risk factors that increases likelihood of being susceptible to disease e.g. CVD risk factor screen - use biomarkers to asses cholesterol levels, screening for alcohol intake in women to prevent breast cancer
Secondary level screening: screening for early features of disease - once disease is already present, allows them to direct treatment before initiation of more serious complications e.g. lung cancer, breast cancer
Tertiary level screening: screening for complications for diagnosed disease e.g. screening for bone density following chemotherapy for breast cancer
HR screening: works with HR groups e.g. sex workers as HR group for HIV
Population based screening: broad group/everyone in population being targeted e.g. breast cancer screening for females within a certain age grou
How do you decide what to screen for?
Is the disease suitable
Is there a suitable test
Is it a suitable program
Is the treatment suitable
Define sensitivity and explain the equation for it
of the people who really do have the disease, how many did you/your test say yes for? Were you sensitive enough to catch everyone? How accurate it is when picking up people who have the disease
Sensitivity eq: TP/(TP+FN) x 100
Define specificity and explain it
of the people who didn't have the disease, how many people did you/your test say didn't? A high specificity means the test will not unnecessarily tell you that you have a certain disease therefore trustworthy
Specificity eq: TN/(TN+FP) x 100
What does PPV and NPV rely on and what do they reflect
The prevalence of the population in which you are applying the test to. Reflects the accuracy and prevalence of the disease
What is the equation for PPV and NPV
PPV eq: TP/(all who test positive) x 100 - the proportion who really have the disease of all people who test positive, the probability of having disease if test is positive
NPV eg: TN/(all who test negative) x 100 - the proportion who are actually free of the disease of all people who test negative, the probability of not having the disease if the test if negative
Explain relationship between prevalence, PPV and test
Higher prevalence = higher PPV = test worked better
Describe lead time bias
Survival as measured from the time of diagnosis may be increased, not because patients live longer, but because screening lengthens the time that they know they have disease - Lead time bias definition: If screening is used, there is an apparent increase in life expectancy - Hence if the screening programme is evaluated in terms of survival time, this may give a false impression of succes
Describe length time bias
Survival time appears longer because screening tends to detect slowly progressing disease and may miss rapidly progressive disease that becomes symptomatic between screening rounds.
Screening identifies 2 patients with rapidly progressive disease and 5 patients with slowly progressive disease
Calculating mean survival from screened patients gives an impression of longer average survival than occurs in the population
Define PAR
Is the amount of extra disease attributable to a particular risk factors in a particular population. If the risk factor is causal, this is the total risk that can be eliminated from a particular population by getting rid of the specific risk factor
In ethnicity coding, what level is the least and most specific
Level 1-least specific
Level 4-most specific
When is it inappropriate to prioritise certain ethnicities over others
During recording
Does reporting have to be done at level 4
NONONO
When an individual responds having multiple ethnicities, what are the ways to record his ethnicities
Total Response Output
Prioritised Output
Sole/combination Output
Describe prioritised output
Each respondent is allocated to a single ethnic group using a priority system
This system is to ensure that where some need exists to assign people to a single ethnic group, ethnic group of policy importance, or of small size, they are not swamped by the NZ European ethnic group.
Frequently used in MoH and health and disability sector for funding calculation, monitoring changes in the ethnic composition of service utilisation and so on. Although, MoH has started to include Total Outputs as one of its ethnicity outputs these days
Explain the pros and cons of prioritised output
Pros
Produces data that are easy to work
Sum of ethnic group population is the total NZ population
Help to collect data on ethnic groups of policy importance, small size so that they are not swamped by the NZ European ethnic group
Cons
Placing people in specific ethnic groups through prioritisation process may simplify but cause biases to the resulting statistics
Over represents some groups at the expense of others.
Maori > Pacific Islander > MELAA (Middle-Eastern, Latin American and African) > NZ European
Maori > Pacific Islander > Asian > Other > NZ/European
Goes against principle of self-identification
What is the order of prioritisation
Maori, pacific, Asian, MELAA, other ethnicities, European
Describe total response output
Individuals who indicate more than one ethnic group are counted more than once, the sum of the ethnic group populations will exceed the total population of NZ
Census uses Total Response Output
Also recommended by Statistics NZ
ONLY COUNT EACH ETHNICITY ONCE IF ASKING AT LEVEL 1. (e.g. someone's total response is recorded as German, Fijian and Samoan -----> NZ/European and Pacific Islander <b>(NOT NZ/European, Pacific Islander, Pacific Islander)</b>)
Note
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