Population health Flashcards
What is the definition of public health?
“The science and art of preventing disease, prolonging life and promoting, protecting and improving health through the organised efforts of society
What is the definition of population health?
The health outcomes of a group of individuals, including the distribution of such outcomes within the group.
What is primary health care? What does it include?
Universally accessible, scientifically sound, first level care provided by a suitably trained workforce. Gives priority to those most in need, maximises community and individual self-reliance and participation. Collaborates with other sectors.
e.g. GP’s
It includes: care of the sick, health promo and illness prevention, advocacy, and communtiy development.
What is global health?
The health of populations in a global context which trascends the perspectives and concerns of individual nations.
e.g. eradicating smallpox.
What is Planetary health?
The health of humanity embedded in the context of human systems; ecosystems, political, economic, and social that shape the future of humanity and the Earth’s natural systems which define the safe environmental limits withing which humanity can flourish
“Far-reaching changes to the structure and fx of Earth’s natural systems represent a growing threat to human health… By unsustainably exploiting nature’s resources, human civilisation has flourished but now risks substantial health effects from the degradation of nature’s life support systems in the future.”
What is Ecohealth?
Conceptualisation and understanding health in its wider environmental or ecosystem context, within a globalising world.
Includes our ecology; our skin gut saliva, our own ecosystems.
Particuarly inportant in Indigenous culture; “Country’s health is our health”.
What is Onehealth?
“Worldwide strategy for expanding interdisciplinary collaborations and communications in all aspects of health care for humans, animals and the environment.”
Something between Ecohealth and Global health; particuarly focusing on emerging infectious diseases.
What is the aim of intention to treat analysis in a clinical trial?
Reduce selection bias
Primary prevention reduces ____
reduces the likelihood of the development of a disease
Secondary prevention _____
prevents or minimises the progress of a disease
Tertiary prevention reduces _____
reduces progression of damage already done
How is rate of a disease development calculated?
(new cases) / (total person time of follow up)
Primary, secondary or tertiary prevention reduces the likelihood of the development of a disease?
Primary prevention
Primary, secondary or tertiary prevention reduces progression of damage already done
Tertiary prevention
How is relative risk calculated?
What does it tell you?
(Risk exposed) / (Risk unexposed)
Re/Ru
indicates the relative magnitude of change in risk/rate of outcome, associated with exposure
Primary, secondary or tertiary prevention prevents or minimises the progress of a disease?
Secondary prevention
What is the aim of blinding in a clinical trial?
Reduce information/observor bias
How is attributable risk percentage calculated?
What does it tell you?
AR% = (Re - Ru)/Re x 100
Proportion of incident disease among exposed people that is due to exposure
What is the aim of randomisation in a clinical trial?
Reduce influence of confounding variables
How is risk calculated?
(Number of new cases in a defined period) / (population at risk)
How is attributable risk calculated?
What does it tell you?
(Risk exposed) - (risk unexposed)
Ru-Re
indicates the absolute magnitude of change in risk/rate of outcome, associated with exposure
What is the “downside”(conservative measure) of intention to treat analysis in a clinical trial?
Underestimates treatment effect
How is population attributable risk percentage calculated?
What does it tell you?
100 x (Rt-Ru)/Rt
Proportion of incident disease among whole population that is due to exposure.
Rt= risk in the whole population which includes both exposed and unexposed.
How is population attributable risk calculated?
(Rate in whole population) - (Ru)
Rt-Ru
What are the 3 essentail features of a clinical trial?
Randomisation
Blinding (aka masking)
Intention-to-treat analysis
What are the 9 Bradford Hill Criteria for causality?
temporal relationship
strength
dose-response relationship
consistency
plausibility
exclude alternatives
experimental evidence
specificity
coherence
How is NNT calculated?
1 / (absolute rate/risk reduction)
1/ARR
How is sensitivity calculated?
True positive
True pos + False Neg
e.g. number of pregnant ladies who peed on the stick and got a positive results, over TP + FN
How is positive predictive value calculated?
True positive
True pos + False Pos
How is specificity calculated?
True negative
True neg + False pos
Specificity of a test is the proportion of healthy patients known not to have the disease, who will test negative for it. Mathematically, this can also be written as: A positive result in a test with high specificity is useful for ruling in disease.
How is negative predictive value calculated?
True negative
True neg + False Neg
What are the axes of a receiver operating characteristic curve?
y = sensitivity
x = 1 - specificity
What is the main purpose of a meta-analysis?
What are the other 3 purposes?
To increase power
• Resolve uncertainty
• Improve estimates of effect size (precision)
• Answer other questions
What should you consider when wondering if a study is relevant to your patient?
PICOT
Population
Intervention
Comparator
Outcome
Time
What are the 4 elements of autonomy in medical ethics?
Freedom to make your own decisions. No coercion No manipulation No deceit
What percentage of travellers visiting a developing country will develop a health problem?
50%
What is the most common cuase of death in travellers?
Cardiovascular disease
Define beneficence in a medical ethics context
Promote health and well-being
What are the 5 ethical principles?
Non-maleficence Beneficence Autonomy Justice Dignity (never be a jerk doctor)
What is the most common serious medical condition in travellers?
Malaria
Define non-maleficence is a medical ethics contect
Do no harm, or minimise harm
Which ethical principle is informed consent most important for?
Autonomy
Define respect for dignity in a medical ethics context
All people are of equal moral worth
What is the most effective public health measure to decrease tobacco usage?
Increasing taxation
How is population atributable risk percentage calculated?
What does it tell you?
100 x (Rt-Ru)/Rt
Proportion of incident disease among whole population that is due to exposure.
Define incidence
Number of new cases of a disease within a specified time period
Define prevalence
Number of exisitng cases of disease at a particular point in time.
It depends on both incidence and duration of disease
Chronic diseases have greater ______ than ______, but diseases with poor survival would have higher_______ than ______.
Chronic diseases have greater prevalence than incidence, but diseases with poor survival would have higher incidence than prevalence.
What is a systematic review?
Lit review paper which analyses multiple papers surrounding single research question.
These studies include RCTs, as well as cohort and observational studies. RCTs are the highest level of evidence.
Inclusion criteria (sub-population, sample size, methodology)- uses consort checklist
“A literature review focused on a single question which identifies, appraises, selects and synthesises high-quality evidence relevant to that question. It is considered the highest level of evidence.”
What is a meta-analysis?
The statistical component of a systematic review (of the many research papers) which includes weighted averages of the papers’ findings. Increases power and confidence of findings (more samples), and decreases uncertainty
May be able to find secondary outcomes.
What does the solid, vertical line represent?
Line of no effect; placebo=txt therefore no difference between the interventions on outcome.
What do the squares-and-lines and diamonds represent?
squares= weighting of the study
lines= confidence interval
diamonds= pool of effect; combined result of the studies
last diamond= overall pooled effect
What is the difference between a type 1 and type 2 error?
T1= false positive
T2= false negative
What is Public Health?
Science and art of preventing disease and improving health through the organised efforts of society
What is Population Health
The health outcomes of a group of individuals, including the distributions of outcomes within the group
What are the three types of prevention?
Primary Prevention- Reduce likelihood of developing diseaseSecondary Prevention- Prevents or minimises progress of diseaseTertiary Prevention- Reduces Progression of damage already done
What is Epidemiology?
Study of Distribution and Determinants of Disease
What is Incidence?
Number of new cases of a disease within a specified time period. Expressed as a rateLongitudinal studies neededPoor Survival will have a higher incidence than prevalence
What is Prevalence?
Number of existent cases of disease at a particular point of time. Expressed as a proportion
What is the prevalence if Incidence and Duration are constant over time?
P=ID
What is Risk?
Probability of disease occurring in a disease free population during a specified time periodRisk= Number new cases/ Population at risk
What is Rate?
Probability of disease occurring in a disease free population during the sum of individual follow up periodsRate = New cases in a defined period total person time / Total person-time of follow up
What is absolute risk/rate
isolated measure of risk/rate (specific)Eg. 5 strokes/10,000 men per year
Formula for Relative Risk?
RR= Re/Ru (exposed/unexposed)Indicates relative magnitude of exposure
Formula for Attributable Risk?
AR= Re-RuIndicates the absolute of change in risk/rate of outcome
What are the features of a cross sectional study?
Sample of population selected at one point in timeEach subject only contributes data once (no follow up)Mostly descriptive outputs
What are the advantages and disadvantages of cross sectional studies?
Relatively cheap and easyneed for representative sampleexplore associations among variables, but no explicit data on temporal relationshipweak evidence of causality
What does the attributable risk percentage represent?
percentage of incident disease among exposed people that was due to the exposureAR/Re x100
How is data collected in cross sectional studies?
Questionnaires, examinations, investigations. Prevalence mainly looked at
What is a case control study?
Comparison of previous exposure status between cases and controls. Looks at the effect of an exposure on an outcome of interst.
What is the purpose of matching during a case control study?
Reduce confound variables having a bias.
What are the advantages and disadvantages of case control studies?
gives explicit knowledge about temporal relationship between exposure and outcome (exposure came before outcome)Useful for studying rare outcomes.
What are cohort studies? Does it use OR or RR?
Longitudinal studies done with follow up of subjects to collect incidence data. Compares outcomes between those exposed and not exposed to a risk factor and relative risks are derived
What are the advantages and disadvantages of cohort studies?
Advantages: explicit and detailed knowledge about temporal relationship b/w exposure and outcome.-Can include multiple exposures and outcomes-cohorts can be established as part of routine clinical careDisadvantages-Difficult for rare outcomes-More difficult and expensive
Why is retrospective cohort study still considered a longitudinal study?
Study is begun at a time where a cohort has already been established and data is available about an exposure in the past
What is Bias?
An Unintentional error due to a systematic difference between or among groups which leads to under or over-estimaion of true results.
What are the two main types of bias?
Selection and Information (measurement)
What is selection bias?
systematic difference in characteristics of people selected for study and those not selected. eg. selecting only people that can speak english. Systematic diff. within groups also lead to selection bias-eg. recruiting cases within hospital but controls outside.
How is selection bias minimised?
careful recruitment (rep. sample of population, and cases and controls from same source)Maximise responseMinimise subjects lost to follow-up
What is information bias?
Systematic difference in how information is collected. Arises when variability in methods of collecting data.
What is recall bias?
Type of information bias where cases are more likely to recall presence of exposure due to already established prejudice about association b/w the risk factor and the outcome.
How is information bias minimised?
Uniform collection methods of information between or among groups being compared.
What is confounding variables? What are two examples?
Influences relationship between exporsure and outcome. A third variable that indepenently affects the outcome, and is related to the exposure. Age and sex are examples.
How is confounding minmised?
Design and execution stages: match by confounder or restriction (eg only select males)Analysis: Stratification and multivariate analyses
How does randomisation help to deal with confounding?
Makes treatment groups identical in all aspects other than the intervention in order to reduce the effect of confounders.
What is intention to treat analysis and what is it used for?
Helps deal with selection bias. People lost to follow up (eg cross over: people started on place start taking drug, or people assigned to drug stop taking it) is a source of selection bias if it is significant. Intention to treat assumes subjects remained in their randomised group, regardless of what the did in real life. Intetnion to treat always under estimates any treatment effect (ie conservative). Cross over introduces overlap in treatment between groups, but ITT ignores this effect, a positive ITT therefore give more confidence.
What is Hazard?
Continuously updated, instantaneous rate which is measured in longitudinal studies with close follow up.HR is Similar to OR and RR, except it does not reflect a time unit of the study.
What is the survival analysis?
During follow, explicitly captures of outcome and their time of occurrence. Survival analysis measure ‘time to event’
What is a Hazard ratio of 0.5?
at any given point in time within the period of followup, the probability of outcome in the intervention group is half of that of the control group.
What is the number needed to treat and how is it calculated?
NNT= number of people needed to undergo the intervention in order to prevent outcome in one. It is a marker of efficiency of the intervention. NNT= 1/(absolute risk or rate reduction)
How do internal and external validity differ?
Internal refers to how well a trial deals with limitations such as bias confounding. External validity refers to the applicatbility of the trial results.
What does PICOT stand for?
P= populationI= InterventionC= Comparator/controlO= OutcomeT= Timing
What is internal validity?
Extent to which the results are valid (accurate, robust etc.) Dependant on study design, data collection and analyses.
What is Stratified Randomisation?
Randomisation by levels of key confounders= eg dividing groups into male and female then randomising from there.
What is the p-value?
Probability that the observed result arose from chance.
What does the width of the 95% confidence interval measure?
Precision of result.
How is external validity assessed?
Determining the degree of concordance between RCT and the clinical setting in terms of PICOT
How do you calculate Odds Ratio
(odds of outcome among exposed)/(Odds of outcome among unexposed)OR= AD/BC
What is the difference between phase 1 and 2 in clinical trials?
Phase 2 targets a larger, unhealthy population with placebo (safety and efficacy) whereas phase 1 is just to a small healthy group (safety and side effects).Test whether it works in phase 2.
What is clinical trial phase three?
Drug given to large group of people, measure effectiveness, monitor side effectsCompare to commonly used treatmentsCollect information that allows the drug to be used safely (Can sometimes be released at 3)
What is Phase IV for clinical trials?
After drug has been marketed. Long term effectiveness and any side effects with long term use. Can be an observation study (ie. seeing performance in other countries before trialling in own)
Which studies contribute the most weight in a meta-analysis?
Larger studies, studies with low CI
What are likelihood ratios?
likehood that a given test result would be expected in a pt with the disease compared to pt w/o the disease
LR of positive test= sensitivity/ (1-specificity)
LR of negative test= (1-senstivity)/specificity
What are the biases involved in screening programs? Explain them.
- Selection bias: the healthy are more likely to be screened
- Lead-time bias: seems to be more effective due to earlier detection, not actual prolonged survival
- Length-time bias: diseases which have a slower progression will be selected for as there is more time to detect the disease (aggressive diseases would cause death a lot earlier)
Odds ratio is most often used in ________ studies
case-control
Relative risk is often used in ______ and ______ studies
Clinical trials and cohort
_______ study - suited to studying causes of rare disease.
Case-control
Sensitivity vs specificity?
Test sensitivity is the ability of a test to correctly identify those with the disease (true positive rate), whereas test specificity is the ability of the test to correctly identify those without the disease (true negative rate).
