Module 2: Deciding on Interventions to Improve PopHlth Flashcards
Frame of Dahlgren and Whitehead (Rainbow) model
Triangle - Population
Rainbow - Understanding effects of SEP and other determinants
Rectangle - Identifying inequalities and inequities and why/how they should be reduced
Time arrows
PHF (public health framework)
Provides max benefit for largest number of people, and reduce inequities in the distribution of health and well-being
Define problem - cross-sectional studies
Identify risk and protective factors - cohort studies, case-controlled studies
Develop and test prevention strategies - RCTs, diagnostic test accuracy studies
Assure widespread adoption - evaluative studies
Causes of causes/determinants - for individuals
Any event, characteristic, or other definable entity, that brings about a change for better or worse in health
May vary at different life stages
Income, employment, education, housing and neighbour hoods, societal characteristics, autonomy, empowerment - social cohesion
Causes of causes/determinants - for populations
Concepts similar as for individuals, but nature of determinants is often different
Related to the context in which the pop exists - different populations exert different characteristics
Downstream vs upstream interventions
Downstream: operate at the micro (proximal) level
e.g. treatment systems, disease measurement
Upstream: operate at the macro (distal) level
e.g. government policies, international trade agreements
Proximal determinants
A determinant of health (downstream) that is proximate/near to the change in health status
Directly associated
e.g. lifestyle, nutrition
Distal determinants
A determinant of health (upstream) that is distant in time and/or place from change in health status
e.g. national, political, cultural factors
3 levels of influence
Level 1: The person
Age, sex, biology, behaviour risk factors, lifestyle
Downstream determinants
Level 2: The community
Local influences, e.g. home, workplace, neighbourhood
Social capital
Wider societal levels, e.g. education and healthcare system
Downstream determinants
Level 3: The environment
Cultural, social, political, physical and built environments
Upstream determinants
Social capital
The value of social networks that facilitates bonds between similar groups of people
Habitus
Learning behaviours by being exposed to the group in which you’re in
4 capitals
Natural, human, societal, financial/physical
All interlinked
Well-being outcomes - individuals
Better physical and mental health
Education outcomes
Labour market outcomes
Housing outcomes
Well-being outcomes - societal
Stronger economic performance
Better democratic functioning, safer communities
More inclusive societies
Structure determinants
Upstream
Social and physical environmental conditions that influence choices and opportunities available
Agency determinants
The capacity of an individual to act independently and make free choices
Empowerment
Individual health care - clinicians
Aim to treat disease - to restore health
Reactive form of treatment
Only interested in people who present to the healthcare
Find cause of symptoms in individual patients
Population healthcare
Concerned with health of groups of individuals, in the context of their environment
Identify and treat all appropriate patients in a population - population approach to clinical practice
Also interested in those who have the disease but don’t know they have it, and those who don’t have the disease (why don’t they have it?)
Social and physical environment of population
Important role of epidemiology
Seek cause of dis-ease
Why establish causal relationships?
Provide support for evidence-based practice
Epidemiology doesn’t determine the cause of a disease in a given individual, instead…
It determines the relationship between a given exposure and dis-ease outcome in populations
Most epidemiological studies are…
Non-experimental and conducted in ‘noisy’ environments in free-living populations, therefore establishing causal interferences should be done cautiously
Causes of low-life expectancy within an impoverished community
High prevalence of health-endangering behaviour (individual level)
Poor education, lack of healthcare (population level)
Cultural disintegration, poverty (societal level)
Why can’t causality be proven in human studies
Practical and ethical reasons
Bradford Hill criteria
Helps establish causality
‘Aid for thought’ - just a guideline, not a checklist
Temporality:
- cause comes before disease
- essential to establish a causal relation
- generally easier to establish from cohort studies
Strength of association:
- measured by size of relative risk
- the stronger the association, the more likely to be causal in absence of known biases
- RR > 2: moderate strong association
- RR > 5: strong association
Consistency of association:
- replication of findings by diff investigators, at diff times, in diff places with diff methods, i.e. multiple studies show similar results –> more likely to be causal
- however, lack of consistency doesn’t exclude a causal association since diff conditions may reduce impact of causal factor in certain studies
Biological gradient (dose-response):
- incremental change in disease rates in conjunction with corresponding changes in exposure
Biological plausibility of association:
- does association make sense biologically?
Specificity of association:
- a cause leads to a single effect or an effect has a single cause
- however, health issues have multiple, interacting causes, and many outcomes share causes
Reversibility:
- the demonstration that under controlled conditions, changing the exposure causes a change in outcome
- ideally assessed by RCT but often not possible
Causal phenomena - complexity
Causal phenomena are usually complex - and exposure - outcome relationships usually not 1:1
Causality is multi-factored
What is a ‘cause of disease’
An event, condition and/or characteristic which play an essential role in producing the disease
Causal pie - components
Sufficient cause (causal mechanism):
- the whole pie
- a minimum set of conditions without any one of which the disease wouldn’t occur
- not usually a single factor; often several
- a disease may have several sufficient causes
Component cause:
- a factor that contributes towards dis-ease causation, but is not sufficient to cause dis-ease on its own
Necessary cause:
- a factor/component cause that must be present if a specific dis-ease is to occur
Causal pie - environment
Every causal mechanism always has some environmental component cause(s)
Causal pie - blocking/removing component causes
Blocking/removing any component cause would result in prevention of some cases of disease
Causal pie - identifying components
Don’t need to identify every component cause to prevent some cases of disease
Knowledge of the complete pathway is not a pre-requisite for introducing preventative measures
Intervening disease
Use association and other factors to infer causation and intervene to prevent disease
Can intervene at any number of points in the pie
Why is need for prevention of disease growing
The need for prevention is growing as the limitations in curing disease become apparent and as the costs of medical care escalate
Types of pop health actions
Health promotion
Disease prevention
Health protection
All of which are split into population based (mass) strategies or high risk (individual) strategies
Population based (mass) strategy
Focuses on whole pop
Aims to reduce health risks/improve outcome of all individuals in pop
Useful for a common disease or widespread cause
High risk (individual) strategy
Focuses on individuals perceived to be a high risk
Intervention is well matched to individuals and their concerns
e.g. NZ needle exchange program –> helps prevent spread of HIV
Pop-based (mass) strategy - advantages and disadvantages
Radical - addresses underlying causes
Large potential benefit for whole pop
Behaviourally appropriate
Small benefit to individuals
Poor motivation of individuals
Whole pop is exposed to downside of strategy (less favourable benefit - risk ratio)
High-risk (individual) strategy - advantages and disadvantages
Appropriate to individuals
Individual (subject and physician) motivation
Cost-effective use of rss
Favourable benefit : risk ratio
Cost of screening; need to identify individuals
Temporary effect
Limited potential
Behaviourally inappropriate
Health promotion
Acts on determinants of well-being Health / well-being focus Empowers people to increase control over and improve their health Involves whole pop in every day contexts Pre-disease
Types of healthcare services
Primary - patient’s regular source of healthcare
Secondary - Specialist care
Tertiary - hospital based care, rehabilitation
Alma Ata 1978: Declaration for primary healthcare
Protect and promote health of all
Advocated a health promotion approach to primary care
1st time social determinants in health was recognised as key to achieving good health in populations
Pre-req for health:
- peace and safety from violence
- shelter
- education
- food
- income and economic support
- stable ecosystem and sustainable rss
- social justice and equity
Ottawa Charter for health promotion (WHO) 1986
‘Mobilise action for community development’
First time human rights was brought to health
Charter acknowledges that health is:
- a fundamental right for everyone
- requires both individual and collective responsibility
- opportunity to have good health should be equally available
- good health is an essential element of social and economic development
Ottawa Charter 1986 - 3 basic strategies
Enable - provide opportunities for all individuals to make health choices through access to info, life skills, and supportive environments (individual level strategy)
Advocate - create favourable political, economic, social, cultural and physical environments by advocating for health and focusing on achieving equity in health (system level strategy)
Mediate - bring together individuals, groups, and parties with opposing interests to work together and come to a compromise for promotion of health (strategy that joins up individuals, groups and systems)
Ottawa Charter 1986 - 5 priority action areas
Develop personal skills Strengthen community action Create supportive environments Reorient health services towards primary health care Build healthy public policy
Disease prevention
Disease focus
Looks at particular diseases and ways of preventing them, e.g. incidence, prevalence, risk factors, or impacts
Natural history of disease and prevention strategies
Biological onset –> Clinical diagnosis –> Recovery, death or disability
Primary (pre-disease) - limit occurrence of disease by controlling specific causes and risk factors
Secondary (post-disease) - reduce more serious consequences of disease
Tertiary (post-disease) - reduce progress of complications of established disease
Health protection
Predominantly environmental hazard focused
Risk/hazard assessment - environmental epidemiology, safe air and water
Occupational health and monitoring
Risk communication
Small risk vs high risk groups
A larger number of people at a small risk may give rise to more cases of disease than the small number who are at a high risk
Prevention paradox
A preventative measure which brings much benefit to the population offers little to each participating individual
Rationale for Maori health promotion
Maori health status/inequalities
Rights as indigenous peoples and treaty partners
‘Mainstream’ health promotion interventions generally less effective for Maori
Maori health is everyone’s responsibility
State of Maori Health - inequalities
Systemic inequalities in…
- health outcomes
- exposure to determinants of health
- health system responsiveness
- representation in health workforce
Ethnic inequalities in health can be reduced, eliminated, and prevented
What causes ethnic health inequalities
Ethnic inequalities in health are fundamentally driven by the unequal distribution of health risks and opportunities (social determinants)
Who has benefited most from health promotion
Dominant cultural populations benefit most; pakeha
Although there is an overall benefit, it only predominantly improves groups already with good health outcomes –> gap widens
What has been the impact of health promotion on Maori health and inequalities
Very little or inequalities have been widened
‘Conventional’ health promotion
Based on Western models
Universal formula
Often simply adapted for Maori
Doesn’t incorporate Maori values and realities
Superficial vs structural approach - ads focus on an educational approach, but misses the fundamental structural approaches, e.g. low income / less privileged communities
Tended to benefit non-Maori to a greater extent
Ottawa Charter - why isn’t it suitable for Maori populations
Has pre-requisites, e.g. peace, shelter, education, food
For Maori pop, must address the pre-reqs (access to basic determinants of health)
Te Pae Mahutonga
A Maori model of health promotion
Based on Southern Cross as a navigational aid
4 central stars (key tasks) and 2 pointers (pre-reqs)
Fundamental components of health promotion from a Maori world view, but might also apply to other NZers
Must address underlying determinants or won’t achieve sustainable change
Te Pae Mahutonga - model
Pre-requisities:
Te Mana Whakahaere (autonomy)
Ngā Manukura (leadership)
Key tasks: Mauriora (cultural identity) Waiora (physical environment) Toiora (healthy lifestyle) Te Oranga (participation in society)
Te Pae Mahutonga - key tasks
Mauriora: access to Te Ao Maori
- e.g. access to Te Reo, Maori language and customs, working together to revitalise traditional Maori practices
Waiora: environmental protection
- physical environments are a key determinant of health
- e.g. pollution, smoke free (indoor) environments like houses and maraes
Toiora: healthy lifestyles
- e.g. diets, smoking, exercise, culturally appropriate ways to help people stop smoking?
Te Oranga: participation in society
- social determinants, ensure we have rss to put above into action
- participation of Maori individually and collectively in political processes
- e.g. education, income, employment
Te Pae Manuhonga - pre-requisites
Te Mana whakahaere:
- enabling capacity for self governance (make decisions for themselves)
- community control and enabling political environment
Ngā Manukura:
- health professional and community leadership
- e.g. collaboration with leaders in communities
Liberation
Remove barriers –> benefits everyone
Maori representation in socio-economic groups
Maori are over-represented in lower socio-economic groups (decile 8, 9, 10) in terms of socio-economic deprivation, e.g. child poverty
Principles of Maori Health promotion
By Maori for Maori/everyone Self determination and control Valid models, frameworks, concepts Maori people, values, collectives Contemporary tools/methods Allows for diverse realities Focus on determinants of health Evidence-based
Screening in health
Involves identifying risk factors for disease or unrecognised disease by applying tests on a large scale to a population
Screening - breast cancer example
Primary: screening women for alcohol intake to prevent breast cancer (screening for risk factors)
Secondary: screening for breast cancer
Tertiary: screening for bone density following chemotherapy for breast cancer
Screening criteria
Suitable disease
Suitable test
Suitable treatment
Suitable screening programme
Objective screening initiative
To improve health outcome (morbidity, mortality and/or disability)
Screening - suitable disease
- An important health problem:
- Relatively common
- Relatively uncommon: early detection and intervention –> better outcome - Knowledge of natural history of disease (or relationship of risk factors to the condition):
- Detectable early (detectable risk factor / disease marker)
- Increased duration of pre-clinical phase
Pre-clinical phase
Period between early features of disease and clinical diagnosis
Screening - suitable test
Reliable - provides consistent results Safe Simple Affordable Acceptable Accuracy - the ability of a test to indicate which individuals have the disease and which do not - (sensitivity, specificity)
Accuracy of a screening test
The Gold standard (diagnostic test):
- in effect the ideal test
- requires clinician, preparation by patient, and must be monitored –> test can’t be applied to large pop groups
- e.g. Colon cancer (Colonoscopy)
Screening test:
- less expensive diagnostic test
- e.g. faecal occult blood test (colon cancer)
Screening - sensitivity
The likeliness of a positive test in those with the disease
The ability of the test to identify those who have the disease (a) from all individuals within the disease (a + c)
Screening - sensitivity equation
true positives/
all with disease
x 100
(expressed as %)
Screening - specificity
The likeliness of a negative test in those without the disease
The ability of the test to identify correctly those who don’t have the disease (d) from all individuals free from the disease (b+d)
Screening - specificity equation
true negatives/
all without disease
x 100
(expressed as %)
Screening - evaluating test accuracy
The sensitivity of a screening test is high if the proportion of true positives is high
The specificity is high if the proportion of true negatives is high
Sensitivity and specificity are a fixed characteristic of the test
Accuracy of a screening test in practice - predictive values
a + b (all people with +ve results)
c + d (all people with -ve results)
Positive predictive value (PPV)
Negative predictive value (NPV)
PPV and NPV are not fixed charactersistics of the test
Reflect both the test accuracy and prevalence of the disease
Positive predictive value (PPV)
The proportion who really have the disease of all people who test positive
The probability of having disease if the test is positive
true positives/
all who test positive
x 100
(expressed as %)
Negative predictive value (NPV)
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 is negative
true negatives/
all who test negative
x 100
(expressed as %)
Screening - suitable treatment
Evidence of early treatment leading to better outcomes
Effective, acceptable and accessible treatment
Evidence-based policies covering who should be offered treatment and the appropriate treatment to be offered
Screening - suitable screening programme
Benefits must outweigh harm
Adequate resourcing and agreed policy for testing, diagnosis, treatment and program management
Cost-effective
Health care system must be able to support all elements of screening pathway
Needs to reach all those who are likely to benefit from it
Lead time bias
If screening program is evaluated in terms of survival time, it may give a false impression of success
Length time bias
Screening identifies 2 patients with rapidly progressive disease and 5 patients with slowly progressive disease
Calculating mean survival from screened patients give an impression of longer average survival than occurs in population
Screening - suitable screening program: RCTs
RCT evidence that screening program will result in:
- reduced mortality
- increased survival time
- – lead time bias
- –length time bias
Eligible population for screening
Those who are likely to have the disease, but don’t have symptoms
Identified by observational studies, RR, and RD
Enter a screening test
Those who test positive –> Gold Standard test
Those who test positive in GS –> intervention/treatment
Those who test negative in GS –> re-screen (after specified time period)
Prevalence and false test results
If prevalence is moderate/low –> higher false positive test results
If prevalence is high –> higher false negative test results
Why are we more likely to pick up the slowly progressing disease during screening than fast progressing disease
Fast progressing may have already died, or may not have started at the time of screening
Why do we need to prioritise in health
Not enough money to fund all health problems
Where does NZ’s health dollar go
Most goes to services of curative and rehabilitative care - rss intensive
Prevention and public health services 7%
Establishing population health priorities
Evidence-based measures:
- descriptive
- explanatory
- evaluative
Community expectations and values
Human rights and social justice
Priorities - evidence-based measures - descriptive
Where are we now? Who is most/least affected?
Major risk factors of disease burden (excluding individual injury risk factors) in NZ
High body mass index Tobacco use High blood pressure High blood glucose Physical inactivity Alcohol
Priorities - evidence-based measures - trends
What are the trends over time? Where have we come from? Where are we going?
Are interventions that are already in place effective or not?
- if current intervention for disease x is effective, will continue with intervention –> money used to fund new intervention for disease y
Priorities - evidence-based measures - explanatory
What are the determinants? Risks? Why are we getting worse/better? Why are pop’s different?
Priorities - evidence-based measures - equity
Does the problem/risk factor disproportionately affect pop sub groups? Why?
Treaty of Waitangi
Epidemiological measures used in prioritisation
Age of death and premature mortality (Years of potential Life Lost to death - YLL)
Time lived with disability (Years Lived with a Disability - YLD)
Population Attributable Risk (PAR)
Risk difference (RD) and attributable risk (AR)
RD = AR = EGO - CGO
i. e. the amount of ‘extra’ disease attributable to a particular risk factor in the exposed group
- incidence in exposed pop (EGO)
Population Attributable Risk (PAR)
The amount of ‘extra’ disease attributable to a particular risk factor in a particular pop
If association is causal: this is the amount of disease (theoretically) we could prevent if we remove that particular risk factor from the pop
Population Attributable Risk (PAR) = ?
Incidence in total pop (PGO) - incidence in unexposed pop (CGO)
PGO = (a + b) / total pop
Priorities - evidence-based measures - evaluative
What can improve health outcomes (and in whom?)
How well can the problem be solved?
- target pop
- expected number in pop who will be reached
- evidence of effectiveness (based on known success rates)
- cost
Priorities - economic feasibility
Does it make economic sense to address the problem?
Are there economic consequences if not carried out?
Priorities - opportunity cost
The health benefits that could have been achieved had the money been spent on the next best alternative intervention or healthcare programme
Priorities - community expectations and value
Public attitudes Human rights and social justice Acceptability: - will the community and/or target pop accept the problem being addressed - competing interests What do communities want (expectations): - confidence in health system - access to necessary care - fair treatment - culturally appropriate - good information about their options
Priorities - community expectations
Access to necessary care
RD vs PAR
RD looks at exposed group –> higher risk prevention strategy
PAR looks at whole pop –> pop based prevention strategy
Prevalence and PAR
Higher prevalence –> higher PAR
