Public Health Flashcards
Advantages case control study
- Good for rare outcomes
- Quicker than cohort or intervention
- Can investigate multiple exposures
Disadvantages case control study
- Difficulty finding controls to match with cases
- Prone to selection and information bias
Case control study
- Compares 2 groups of people
- Groups with and without the disease are selected and their past exposures are identified- a retrospective study
cohort study
- Longitudinal study
- Follows participants over period of time
- a sample is taken from the study population (those at risk of outcome) and split into subgroups, one being exposed and the other not being exposed. Incidence of the disease amongst the sub groups is later compared.
Advantages cohort study
- Can follow up a group with a rare exposure
- Good for common and multiple outcomes
- Less risk of selection and recall bias
Disadvantages cohort study
- Takes long time
- Loss to follow up
- Large sample size needed
Cross sectional studies
Looks at data at a single point in time
- exposure and outcome are measured simultaneously in a given population at a particular point in time
Advantafes cross sectional
- Quick and cheap
- Provide data on prevalence at single point in time
- Large sample size
- Good for surveillance and PH planning
Disadvantages cross secional
- Risk of reverse causality
- Cannot measure incidence
- Risk recall bias and non-response
RCT
- Subjects are randomly assigned to groups
- a sample from the population is split into two groups, one group is given treatment and the other is the control group.
Advantages RCT
- Low risk of bias and confounding
- Can infer causality
RCT disadvantages
- Time consuming
- Expensive
- Specific inclusion/exclusion criteria may mean study population different from typical patients
Selection bias
Systemic error in
- Selection of study participants
- Allocation of participants to different study groups
- Non response
- Loss to follow up
Information bias
- Measurement
- Observer
- Recall
- Reporting
Publication bias
- Not all trial results are published
Confoudning
- Estimate between an exposure and an outcome is distorted because of the association of the exposure with another factor that is also independently associated with the outcome
Reverse causality
- Association between an exposure and an outcome could be due to the outcome causing the eposure rather than the exposure causing the outcome
Sensitivity
a/(a+c)
a = +ve screening test and have disease TP
c = negative screening test and have disease FN
= those with the disease who are correctly identified
Specificity
d/(b+d)
d = negative test and dont have disease TN
b = positive screening test and dont have disease FP
- proportion of people without the disease who are correctly excluded by the screening test
PPV
a/(a+b)
a= +ve test and have TP
b = +ve test and dont FP
= proportion of people with +ve test who have the disease
NPV
d/(d+c)
d = -ve test and dont have TN
c = -ve test and do have FN
= Proportion with a -ve test who do not have disease
NHS criteria for screening test
The condition
- Important
- Epid understood
- Primary prevention implemented
- Mutation
Screening
- ongoing
- Cost balanced in relation to spending as a whole
Test
- Safe test
- Test values known and cut off defined
- Acceptable to population
- Further ix agreed
Treatment
- Effective treatment/intervention
- What and who to offer to
- Outcomes optimised
Lead time bias
When screening identifies an outcome earlier than it would otherwise have been identified this results in an apparent increase in survival time even if screening has no effect on outcome
Length time bias
- Differences in the length of time taken for a condition to progress to severe effects, that may affect the apparent efficacy of a screening method
Health needs assessment - epidemiological approach
- Disease incidence and prevalence
- Morbidity and mortality
- Life expectancy
- Services available
- Sources of data
advantages - Uses existing data and provides data on disease
- Can evaluate over time
disadvantages - Quality of data variable
- May not be data required
HNA - corporate approach
- Ask local population what health needs are
- Focus groups, interviwes…
- Wide variety of stakeholders
advantages - Based on population needs
- Wide range of views
disadvantages - Difficult to distinguish need rom demand
- Vested interest
- Political agendas
HNA - comparative approach
- Compare health or healthcare provision of 1 pop to another
- Spatial or social
Advantages - Quicj and cheap if data available
Disadvantages - Difficult to find comparable populaiton
The 3 domains of public health
- Health improvement
- Health protection
- Health service quality
Indivisual level interventions
- e.g. childhood immunisations
Ecological level interventions
- e.g. clean air act
- General interventions and not specifically delivered at the individual level
Community level
- Similar to ecological level interventions but delivered al local/community level
- e.g. playground for local community
Horizontal equity
- Equal treatment for equal need
Vertical equity
- Unequal treatment for unequal need
Health needs assessment
- Systemic method for reviewing the health issues facing a population
- Leads to agreed priorities and resource allocation that will improve health and reduce inequalities
Framework for health service evaluation
- Structure = what is there
- Process = what is done
- Outcome = morbidity, mortality, QOL
Classification of health outcomes
- Mortality
- Morbidity
- QOL
- Patient satisfaction
Maxwell’s dimensions of quality
- Acceptability
- Accessibility
- Appropriateness
- Effectiveness
- Efficiency
- Equity
Qualitive methodology
- Observation
- Interviews
- Focus group
- Review of documents
Incidence
- New cases
- Denominator
- Time
Prevalence
- Existing cases
- Denominator
- Point in time
Attributable risk
- Rate of disease in the exposed that may be attributed to the exposure
Relative risk
- Ratio of risk of disease in the exposed to the risk in the unexposed
Primary prevention
- Prevent a disease from occurring by reducing exposire or risk factors
- Lifestlye
- Vaccines
Secondary prevention
- Detect early disease to alter course
- Treatment with aspiring to prevent recurrence of MI
Tertiary prevention
- Minimise disability
- Stroke rehab
what 3 factors determine an individuals health behaviour
- Attitude
- Behaviour
- Subjective norms and percieved behavioural control
Wilson and junger criteria for screening
Condition
- must have latent stage
- natural history is understood
Test
- Suitable
- Acceptable
- Interval determined
Treatment
- Acceptable
- Facilities available
Other
- Cost effective
- Risk outweighs benefits
- Agreed policy on who to treat
Health behaviours 3
- Health behaviour - behaviour aimed at preventing disease
- Illness behaviour - behaviour aimed to seek remedy
- Sick role behaviour - any activity aimed at getting well
externality theory of obesity
Normal weight people respond to internal homeostatic cues
Overweight individuals respond to external cues, time of day, sensory food cues
Weaknesses- theory is too generalised
restraint theory
Dieters stop eating at their cognitive diet boundary, before they reach satiety
Overtime dieters get a larder range between hunger and satiety
If dieters exceed the diet boundary they will continue to eat until satiety (which is higher than a normal eater) leading to weight gain
Weaknesses- suggests a rigid diet plan
Domestic abuse risk
Standard risk: Does not suggest imminent serious harm 🡪 signpost
Moderate risk: Potential for serious harm but unlikely unless there is a change in circumstances 🡪 signpost
High risk: Imminent risk of serious harm 🡪 MARAC/IDVAS
Health belief
- Beleive susceptible
- Believe disease has serious consequences
- Believe that taking action reduces susceptibility
- Believe that benefit outweighs cost
Theory of planned behaviour
- Intention is the most important aspect
- Determined by attitude, social pressure and percieved behaviour control
Social norms
- Re-align perceptions of norms with reality
- Used in adolescents
Transtheoretical model
- Pre contemplation
- Contemplation
- Preparation
- Action
- Maintenance
felt need
individual perceptions of variation from normal health
expressed need
individuals seeking help to overcome variation from normal health
normative need
professionals define interventions/approach for expressed need
comparative need
relative to a reference or peer group
transition points in life
- becoming a parent
- becoming unemployed
- bereavement
- leaving school
