Public health Flashcards
What are the 3 concerns of public health?
Inequalities in health
Wider determinants of health
Prevention
What are the 3 domains of public health
Health improvement
Health protection
Service improvement
How can health interventions be applied?
Delivered at an individual level (i.e. vaccinations to prevent an individual from getting ill)
Delivered at a community level (i.e. opening a new outdoor play area in a particular town)
Delivered at a population level (i.e. putting iodine in salt to prevent iodine deficiency)
What needs to be done/performed before a health intervention is made?
Health needs assessment
What is a health needs assessment?
A systematic method for reviewing the health issues facing a population
Leading to agreed priorities and resource allocation that will improve health and reduce inequalities
What are the three approaoches of health needs assessment?
- Epidemiological (considers the burden of illness in terms of the incidence, prevalence, and mortality of a disease or health condition. This approach also draws on estimates of clinical and cost effectiveness from systematic reviews of well-designed studies)
- Comparative (Compares the services received by a population (or subgroup) with others)
- Corporate (the systematic collection of the knowledge and views of local health professionals and users of health services on health-care services and needs)
What is a health care need?
The ability to benefit from a health care intervention
What are the four sociological approaches to need?
Felt need – individual perceptions of variation from normal health
Expressed need – individual seeks help to overcome variation in normal health (demand)
Normative need – professional defines intervention appropriate for the expressed need
Comparative need - comparison between severity, range of interventions and cost
What is primary prevention? example?
Preventing a disease before it has happened eg DRINKAWARE, change4life
Vaccinations. Counseling to change high-risk behavior.
What is secondary prevention? example?
Catching a disease in its pre-clinical or early clinical phase eg screening
What is tertiary prevention? example?
preventing complications of a disease eg diabetic foot care, eye reviews in diabetes, attending physio after stroke
What is secondary prevention in myocardial infarction?
NICE produced guidelines on the management of patients following a myocardial infarction (MI) in 2013.
All patients should be offered the following drugs:
dual antiplatelet therapy (aspirin plus a second antiplatelet agent)
ACE inhibitor
beta-blocker
statin
What are the two approaches to prevention?
Population approach – preventative measures e.g. dietary salt reduction through legislation to reduce BP, adding iodine to salt to prevent iodine deficiency
High risk approach – identifying individuals above a chosen cut-off and treat e.g. screening for hypertension,
What is meant by the prevention paradox?
A preventative measure which brings much benefit to the population often offers little to each participating individual
i.e. it’s about screening a large number of people to help a small number of people
What are the different types of screening?
Population-based screening programmes (e.g. cervical cancer, breast cancer)
Opportunistic screening (e.g. performing BP measurements in GP)
Screening for communicable disease
Pre-employment and occupational medicals
Commercially provided screening (where you can pay to get your blood sent off and tested for all sorts of genetic problems)
Genetic counselling (i.e. genetic testing for people with FHx of genetic disease)
Disadvantages of screening?
Exposure of well individuals to distressing or harmful diagnostic tests
Detection and treatment of sub-clinical disease that would never have caused any problems
Preventative interventions that may cause harm to the individual or population
What is the sensitivity of a screening program and how do you calculate it?
The proportion of people with the disease who are correctly identified by the screening test
True positive / (true positive + false negative)
What is the specificity of a screening program and how do you calculate it?
The proportion of people without the disease that are correctly excluded by the screening test
True negative / (true negative + false positive)
What is the positive predicted value and how is it calculated?
The proportion of people with a positive test result who actually have the disease
True positive / (true positive + false positive)
What is the negative predictive value and how is it calculated?
The proportion of people with a negative test result who do not have the disease
True negative / (true negative + false negative)
This is lower if the prevalence is higher
Antenatal child health surveillance
Ensure intrauterine growth
Check for maternal infections e.g. HIV
Ultrasound scan for fetal abnormalities
Blood tests for Neural Tube Defects
Newborn child health surveillance
- Clinical examination of newborn
- Newborn Hearing Screening Programme e.g. oto-acoustic emissions test
- Give mother Personal Child Health Record
First month and following months child health surveillance
- Heel-prick test day 5-9 - hypothyroidism, PKU, metabolic diseases, cystic fibrosis, medium-chain acyl Co-A dehydrogenase deficiency (MCADD)
- Midwife visit up to 4 weeks
- Health visitor input
- GP examination at 6-8 weeks
- Routine immunisations
Pre school child health surveillance
National orthoptist-led programme for pre-school vision screening to be introduced
What is a cross-sectional study?
Snapshot data of those with and without disease to find associations at a single point in time
What is a case control study?
Retrospective observational study which looks at a certain exposure and compares similar participants with and without the disease
selects absed on DISEASE
What is a cohort study?
Longitudinal study which takes a population of people recording their exposures and conditions they develop
can be prospective or retrospective
selects based on EXPOSURE
What is a randomised control trial?
Similar participants randomly controlled to intervention or control groups to study the effect of the intervention
What is prevalence
measuring existing cases
What is point prevalence?
number of cases of disease at a point in time / total number of people in the defined population at the same point in time
what is period prevalence?
Period prevalence is the number of individuals identified as cases during a specified period of time, divided by the total number of people in that population.
What can increase prevelence?
screening programmes identifying new cases
increasing risk factors
increased life-expectancy due to better treatments can increase prevalence
What is incidence?
The number of new cases per unit time (can be expressed as a percentage or per e.g. 100,000). e.g. 100,000 new cases per year
What is incidence rate?
Number of persons who have become cases in a given time period / total person-time at risk during that period eg 3/32 = 9.4 per 100 person years
What is absolute risk?
the incidence divided by the population.
Gives a feel for the actual numbers involved i.e. has units (e.g. 50 deaths/ 1000 population)
What is attributable risk?
The rate of disease in the exposed that may be attributed to the exposure
Attributable risk = incidence in exposed – incidence in unexposed
It’s about the size of the effect in absolute terms – gives a feel for the public health impact if causality is assumed
The attributable risk:
AR = (A/(A+B)) – (C/(C+D))
The attributable risk percentage of smoking can be calculated as:
AR % = AR / (A/(A+B)) x 100
This means 53.31% of incidence of cardiovascular disease among smokers is attributable to their smoking.
What is relative risk?
Ratio of risk of disease in the exposed to the risk in the unexposed
Relative risk = incidence in exposed / incidence in unexposed
Tells us about the strength of association between a risk factor and a disease
Relative risk of 1.74 = 74% more likely
An RR of 1.00 means that the risk of the event is identical in the exposed and control samples. An RR that is less than 1.00 means that the risk is lower in the exposed sample. An RR that is greater than 1.00 means that the risk is increased in the exposed sample.
What is relative risk reduction?
The reduction in rate of the outcome in the intervention group relative to the control group
1 minus RR
(incidence in non exposed – incidence in exposed) / incidence in non-exposed
What is absolute risk reduction?
The absolute difference in the rates of events between the 2 groups
Gives an indication of the baseline risk and the intervention effect
Incidence in nonexposed – incidence in exposed
i.e. assuming exposed means they have had a particular intervention (such as giving statins to people with hypercholesterolaemia and then a control group who do not have statins and seeing how many in each group have a heart attack to see if the intervention of statins is effective
What is number needed to treat?
the number of patients we need to treat to prevent one bad outcome
NNT = 1/(risk in non-exposed – risk in exposed)
Aka 1/absolute risk reduction
When is odds ratio used?
For case control studies it is not possible to calculate the relative risk and so the odds ratio is used.
For cross-sectional and cohort studies both can be derived but odds ratio is used if it is not clear which is the IV and which is the DV because it is symmetrical.
What is odds?
The odds of an event is the ratio of the probability of an occurrence compared to the probability of a non-occurrence.
Odds = probability/(1-probability)
eg probability = 0.75
Odds = 0.75/(1-0.75)
Odds = 3
Interpretation of odds ratio?
OR=1 Exposure does not affect odds of outcome
OR>1 Exposure associated with higher odds of outcome
OR<1 Exposure associated with lower odds of outcome
What is cumulative incidence/risk
number of new cases in a time period/ number of disease free people at the start of the time period.
Cohort study would do this
Denominator is disease-free people
It is a proportion.
Time period must be stated.
Closed population/cohort
What is incidence odds/odds of disease?
number of new cases of disease in time period/ number of people who were still disease free at the end of the time period so is probability of disease/probability of not getting disease.
Eg 25/75 if 25 out of 100 get disease. Odds of disease
Define epigenetics
The expression of a genome depends on the environment
Define allostasis and allostatic loads
The same as homeostasis, the stability through change of our physiological systems to adapt rapidly to change in environment
Allostatic load: Long-term overtaxation of our physiological systems leading to impaired health (stress)
Define salutogenesis
Favourable physiological changes secondary to experiences which promote healing and health
Define emotional intelligence
The ability to identify and manage one’s own emotions, as well as those of others
What is health psychology?
Emphasises the role of psychological factors in the cause, progression and consequences of health and illness
Aims to put theory into practice by promoting healthy behaviours and preventing illness
What are the three categories of behaviour in health psychology ?
Health behaviour is a behaviour aimed to prevent disease
Illness behaviour is aimed at seeking remedy eg going to doctor
Sick role behaviour is any activity aimed at getting well eg taking medication
What is health behaviour
a behaviour aimed to prevent disease
What is illness behaviour?
a behaviour aimed at seeking remedy eg going to doctor
What is sick role behaviour?
any activity aimed at getting well eg taking medication
What is the theory of unrealistic optimism
Individuals continue to practice health damaging behaviours due to inaccurate perceptions of risk and susceptibility
- Lack of personal experience
- Belief that preventable by personal action
- Belief that if it’s not happened by now, it’s not likely to
- Belief that the problem is infrequent
What is the health belief model of behaviour change?
Individuals will change if they think:
1. Perceived susceptibility
2. Perceived severity/consequences
3. Perceived benefits
4. Perceived barriers (cost<benefit)
What are cues to behaviour change?
Internal - getting older, MI, perception of health
External - loss of a family member, public health messaging, doctor opinion
it is part of the health belief model but isn’t always included - critique when not included
What is self-efficacy?
The belief in their ability to carry out a preventative behaviour
What is outcome expectancy?
Whether the person feels they will be healthier as a result of their action
What is the theory of planned behaviour?
Proposes that the best predictor of behaviour is ‘intention’ eg i intend to give up smoking.
Intention are determined by:
- Attitudes A person’s attitude to the behaviour
- Subjective norm The perceived social pressure to undertake the behaviour, or subjective norm (messages from significant others)
- Perceived behavioural control A person’s appraisal of their ability to perform the behaviour, or their perceived behavioural control (psychological and physical barriers can influence this)
What is the transtheoretical model or stages of change model
- Precontemplation
- Contemplation (thinking about it sometime in the future)
- Preparation (28 days)
- Action (6 months)
- Maintenance (6 months)
What is the theory of social norms?
Our health behaviours are guided by our perception of social norms. We are more likely to do what we think everyone else is doing even if this isn’t accurate.
NICE transition points where behaviour change may be effective
Leaving school
Entering the workforce
Becoming a parent
Becoming unemployed
Retirement and bereavement
Equation for working out units of alcohol
(% alcohol by volume x amount of liquid in millimetres) divided by
1,000
or litres x % alcohol
Equation for working out BMI?
weight (kg) divided by (height (m) squared)
First line for smoking cessation
- have a target stop date
- prescribe NRT, varencline or bupropion
- prescription to last until just after stop date
- If unsuccessful, don’t offer repeat prescription within 6 months
three pharma options for smoking cessation?
Nicotine replacement therapy
Varenicline
Bupropion
Forms of NRT?
patches, gum, inhalator, lozenge or nasal spray
offer a combo if high dependencne/not worked in past
adverse effects of NRT?
nausea & vomiting, headaches and flu-like symptoms
What is varencicline?
a nicotinic receptor partial agonist
should be started 1 week before the patients target date to stop
the recommended course of treatment is 12 weeks (but patients should be monitored regularly and treatment only continued if not smoking)
varenicline should be used with caution in patients with a history of depression or self-harm. There are ongoing studies looking at the risk of suicidal behaviour in patients taking
varenicline
contraindicated in pregnancy and breast feeding
Side effects varenicline?
nausea is the most common adverse effect. Other common problems include headache, insomnia, abnormal dreams
What is bupropion
a norepinephrine and dopamine reuptake inhibitor, and nicotinic antagonist
should be started 1 to 2 weeks before the patients target date to stop
small risk of seizures (1 in 1,000)
contraindicated in epilepsy, pregnancy and breast feeding. Having an eating disorder is a relative contraindication
Interventions for smoking cessasion in pregnancy?
- cognitive behaviour therapy, motivational interviewing or structured self-help and support from NHS Stop Smoking Services
- NRT if the above measures failure. There is no evidence that it affects the child’s birthweight. Pregnant women should remove the patches before going to bed
What is in the 6 in 1 vaccine?
- diptheria
- tetanus
- polio
- pertussis
- haemophilus influenzae type B (HiB)
- Hepatitis B
What is in the 4 in 1 vaccine?
- diptheria
- tetanus
- polio
- pertussis
What is in the 3 in 1 vaccine?
- diptheria
- tetanus
- polio
8 week vaccinations?
- 6 in 1 vaccine
- Meningococcal type B
- Rotavirus (oral vaccine)
12 week vaccinations?
- 6 in 1 vaccine (again)
- Pneumococcal (13 different serotypes)
- Rotavirus (again)
16 week vaccinations?
- 6 in 1 vaccine (again)
- Meningococcal type B (again)
1 year vaccinations?
- 2 in 1 (haemophilus influenza type B and meningococcal type C)
- Pneumococcal (again)
- MMR vaccine (measles, mumps and rubella)
- Meningococcal type B (again)
Yearly vaccine from age 2 – 8
Influenza vaccine (nasal vaccine)
3 years 4 months vaccine
4 in 1 (diphtheria, tetanus, pertussis and polio)
MMR vaccine (again)
Vaccine 12-13 years
Human papillomavirus (HPV) vaccine (2 doses given 6 to 24 months apart)
Vaccine 14 years?
3 in 1 (tetanus, diphtheria and polio)
Meningococcal groups A, C, W and Y
Institute of medicine 6 aims of quality?
Safe
Effective
Patient-centred
Timely
Efficient
Equitable
What are the 2 types of equity?
Horizontal equity – equal treatment for equal need (people with the same disease should be treated equally)
Vertical equity – unequal treatment for unequal need (e.g. areas with poorer health may need higher expenditure on health serviceS)
How much alcohol is in a unit?
8g
Maxwell classification for quality of health services
3 A’s and 3 E’s:
Acceptability – how acceptable is the service for people needing it
Accessibility – geographical access, costs for patients, waiting times
Appropriateness – right treatment given to the right people?
Effectiveness – does the intervention produce the desired effect?
Efficiency – is the output maximised for a given input?
Equity – are patients being treated fairly?
What are the three things that make up the framework for health service evaluation?
Structure (buildings, staff, equipment)
Process (number of pts seen, number of operations perfomed)
Outcome (mortality, morbitity, PROMS, 5 Ds)
What is a meta analysis?
Take lots of studies and combine the results (statistical procedure)
What approaches can be used to help people act on their intentions?
Perceived control – ask them to reflect on how they felt when something went well (i.e. when they said no to a cigarette)
Anticipated regret – ask them to reflect on how they felt when they didn’t do something (i.e. when they weren’t able to say no to a cigarette)
Preparatory actions – remind people to prepare for their change of behaviour (i.e. throwing away cigarettes)
Implementation intentions – help them help themselves incorporate the behaviour change into their routine (i.e. putting tablets next to the kettle so they know to take it when they make a cup of tea)
What strain of e.coli is most dangeorus
e.coli O157
Levels of maslows hierarchy of needs
Physiological – breathing, food, water, sleep
Safety – security of employment, resource’s, family, health, property
Love/belonging - friendship, family, sexual intimacy
Esteem – self-esteem, confidence, achievement, respect of others
Self-actualisation - morality, creativity, spontaneity, problem solving, lack of prejudice, acceptance of facts
define asylum seeker
A person who has made an application for refugee status
Define refugee
A person granted asylum and refugee status, usually means leave to remain for 5 years and then re-apply
What 4 questions need to be asked when negligence is suspected?
Is there a duty of care?
Was there a breach in that duty?
Did the patient come to any harm?
Did the breach cause the harm?
What are 2 tests that can be used to decide whether there was a breach in a duty of care?
Bolam test = would a group of responsible doctors do the same?
Bolitho test = would it be reasonable of them to do so?
What are the features of Kolb’s learning cycle?
Experience (activist)
Review, reflect on experience (reflection)
Conclusions from experience (theorist)
What can I do differently next time? (pragmatist)
article 2 human rights
the right to life (limited)
article 3 human rights
the right to be free from inhumane and degrading treatment (absolute)
article 8 human rights
the right to respect for privacy and family life (qualified)
article 12 human rights
right to marry and found a family
What are the GMC duties of a doctor?
Make the care of your patient your first concern
Protect and promote the health of patients and the public
Provide a good standard of practice and care - keep professional skills up to date, recognise limits of competence, work with colleagues to serve patients best interests
Treat patients as individuals and respect their dignity and confidentiality
Work in partnership with patients
Be honest, open and act with integrity – act without delay if you believe a colleague is putting patients at risk
What is meant by primary, secondary and tertiary intention with respect to wound healing?
Primary intention – little or no tissue loss, wound edges directly opposed (linear scarring)
Secondary intention – wound edges not oppose, would allowed to granulate, epithelialisation occurs from edge of hair follicle remnants in the base of the wound
Tertiary intention – wound is purposefully left open e.g. infection, foreign body, initially cleaned, debrided and observed. Surgically closed later
4 stages of wound healing?
Vascular response
Inflammatory response
Proliferation
Maturation
What is the definition of domestic abuse?
Controlling, coercive, threatening behaviour, violence of abuse between those aged 16 or over who are or have been intimate partners or family members
Includes – psychological, physical, sexual, financial and emotional abuse
What tool can be used to assess domestic abuse?
DASH tool (Domestic abuse and Sexual Harassment tool)
What do you do if you think someone is at medium/standard risk of domestic abuse?
in these cases it’s their CHOICE what they do
Give them contact details for domestic abuse services and let them decide what to do
calculate attributable risk and attributable risk percentage :
disease no disease
smoked 25 140
non-smoked 52 683
The attributable risk of smoking can be calculated as:
AR = (A/(A+B)) – (C/(C+D))
AR = (25/(25+140)) – (52/(52+683))
AR = .08077
The attributable risk percentage of smoking can be calculated as:
AR % = AR / (A/(A+B)) * 100
AR % = .08077 / (25/(25+140)) * 100
AR % = 53.31%
This means 53.31% of incidence of cardiovascular disease among smokers is attributable to their smoking.
What is odds ratio?
The odds ratio is the ratio of odds for exposed group to the odds for the not exposed groups.
Odds ratio = (AxD) / (BxC)
value > 1 is positive
Physiological changes renal - pregnancy
Increased perfusion to kidneys (up 30%) → increased GFR (up 30-60%)
Urine : increased protein, increased urea, increased creatinine, trace glucose
Serum: decreased urea, decreased creatinine, reduced albumin
If trace glucose, may offer OGTT at 24 weeks
Physiological changes respiratory - pregnancy
Increased oxygen demands, progesterone increases sensitivity of respiratory centre to CO2
Tidal volume increases
Respiratory rate increases
Physiological changes hematology - pregnancy
There is increased red blood cell production in pregnancy, leading to higher iron, folate and B12 requirements. There is also an increase in calcium req but body absorbs better too so may be unchanged
Plasma volume increases > red blood cell volume, leading to a lower concentration of red blood cells. High plasma volume means the haemoglobin concentration and red cell concentration (haematocrit) fall in pregnancy, resulting in anaemia.
Lower Hb
Lower platelets
Clotting factors such as fibrinogen and factor VII, VIII and X increase in pregnancy, making women hyper-coagulable (ready for delivery). This increases the risk of venous thromboembolism (blood clots developing in the veins). Pregnant women are more likely to develop deep vein thrombosis and pulmonary embolism.
Placental secretion
High ALP (up to 4 times higher)
Physiological changes skin and hair - pregnancy
Increased skin pigmentation due to increased melanocyte stimulating hormone, with linea nigra and melasma
Striae gravidarum (stretch marks on the expanding abdomen)
General itchiness (pruritus) can be normal, but can indicate obstetric cholestasis
Spider naevi (related to increased estrogen)
Palmar erythema
Postpartum hair loss is normal, and usually improves within six months.
Physiological cardiovascualr changes pregnancy
Increased blood volume Increased cardiac output
Higher heart rate
Ejection systolic murmur
Third heart sound
Decreased pulmonary vascular resistance
Decreased diastolic blood pressure in early and middle pregnancy, returning to normal by term (blood being diverted to placenta)
Peripheral vasodilation → oedema (increased levels of estrogen and progesterone) could also be caused by an enlarged uterus impeding venous return
Principles of parkinsons management
Motor symptoms affecting everyday life : levodopa
Motor symptoms not affecting everyday life: dopamine agonist, levodopa or MAO-B
Levodopa: better at treating motor symptoms, causes more motor SEs
Dopamine agonist
Examples: bromocriptine, cabergoline, apomorphine, ropinirole
Worse at treating motor, less motor SEs, more adverse events
Ergot-derived (bromo and carbo) can cause fibrosis
MAO-B
Example: selegiline
Worse at treating motor, less motor SEs, less adverse events
what are ecological studies?
Ecological studies are carried out at the group or area level where exposure and
outcome is determined for groups (in this case the population living in each census
area) rather than for individuals.
Error due to failure to consider alternatives
Is typically when one abnormality is
found that fits a particular diagnosis and so you stop searching for other potential clues that may change
your differential.
Error of overattachment
Is conducting tests to confirm what we expect or want to see
and not ruling out other causes
Error of bravado
Is typically working above competence in a show of
over confidence that is not safe. E
Error of ignorance
Unconscious incompetence
Seedhouse ethical grid
Core rationale (patient preference, autonomy)
Deontological layer (beneficience/non-malifecence)
Consequential layer (justice/utilitarianism)
External considerations (law, resources, guidelines)
sloth based error
being lazy eg not checking results
error of comission
doing something wrong eg prescribe the wrong drug
error of omisson
doing something wrong because you didn’t do something
Investigators find a high level of correlation between levels of socioeconomic
deprivation and cardiovascular mortality across electoral wards in the UK.
ecological study
Researchers set out to examine the association between alcohol consumption
and stroke. They identify all new patients admitted with stroke and compare
their alcohol consumption with patients admitted for elective surgery.
case control study
General practitioners set up a study to estimate the prevalence of depression
within their registered population. They decide to start with a random sample
of adults aged 45-74 years. .
cross-sectional
AAA screening program
Men over 65 are invited
no enlargement - never tested again
small 3cm to 4.4cm- tested every year
medium 4.5cm to 5.4cm across.- test every 3 months
large 5.5cm or more across. - rf to surgeon within 2 weeks
Bowel cancer screening
everyone 60-74, expanding to be 50+
FIT test every 2 years
Breast cancer screening
women aged 50-71
mammogram every 3 years
Diabetic eye screening
everyone older than 12 with diabetes
once per year
Fetal Anomaly Screening Programme (FASP)
20 week scan checking for anomalies such as:
Edwards’ syndrome (T18)
Patau’s syndrome (T13)
anencephaly
spina bifida
cleft lip
congenital diaphragmatic hernia
gastroschisis
exomphalos
congenital heart disease
bilateral renal agenesis
lethal skeletal dysplasia
Infectious diseases in pregnancy screening (IDPS)
booking appt
HIV
Hep b
Syphilis
steps of satiety cascade
sensory
cognitive
pre-ingestion
post-absorptive
what is lead time and length time bias
lead time - survival looks better beacuse screening picks things up earlier than they would clinically present
length time - survival looks better becuase screening picks up slowly progressing disease as well as rapidly progressing instead of just rapidly progressing presenting clinically
“the length of time to die would have been longer!”
what is ecological fallacy
Drawing conclusions about individuals from data on groups
mismatch that arises from trying to draw conclusions about individual-level epidemiological associations from a group-level study
wilson and junger criteria screening
Disease must be an important problem
Disease must have a known and detectable latent phase
Disease must have a known natural course and progression
There must be a test which is acceptable to the population
There must be a treatment for the disease
There must be an agreed at-risk population of which to screen
There must be an agreed policy on who to treat
The cost of the screening should be economically balanced
what is the materialist model of health inequalities
Poverty exposes people to health hazards.
Disadvantaged people are more likely to live in areas where they are exposed to harm such as air-pollution and damp housing.
what is the indirect selection model of health inequalities
The idea that an individual’s health can influence their social mobility and, hence, their position in the social hierarchy
What is the cultural-behavioural model of health inequality?
culture determines or frames behavioural choices, including decisions affecting health, i.e., engaging in higher risk lifestyles that may include drinking, smoking, or an unhealthy diet
Bradford-Hill criteria of study of causation
STD CRAP
Strength of Association – relative risk
Specificity – relationship specific to outcome of interest
Temporality – dose exposure precedes outcome
Dose-Response – higher exposure correlates to higher risk of
disease
Consistency – similar results from different researchers
Coherence – logical consistency with other information
Reversibility – removal of exposure reduces risk
Analogy – similarity with other established cause-effect relationships
Plausibility - Biological Plausibility – mechanism to explain the link
what are the 12 human factors that contribute to error?
the dirty dozen
fatigue
stress
pressure
distraction
complacency
norms
lack of knowledge
lack of awareness
lack of teamwork
lack of assertiveness
lack of communication
lack of resources
What is point prevalence?
number of cases of disease at a point in time / total number of people in the defined population at the same point in time
what is period prevalence?
Period prevalence is the number of individuals identified as cases during a specified period of time, divided by the total number of people in that population.
What can increase prevelence?
screening programmes identifying new cases
increasing risk factors
increased life-expectancy due to better treatments can increase prevalence
What is incidence?
The number of new cases per unit time (can be expressed as a percentage or per e.g. 100,000). e.g. 100,000 new cases per year
What is incidence rate?
Number of persons who have become cases in a given time period / total person-time at risk during that period eg 3/32 = 9.4 per 100 person years
What is absolute risk?
the incidence divided by the population.
Gives a feel for the actual numbers involved i.e. has units (e.g. 50 deaths/ 1000 population)
What is attributable risk?
The rate of disease in the exposed that may be attributed to the exposure
Attributable risk = incidence in exposed – incidence in unexposed
It’s about the size of the effect in absolute terms – gives a feel for the public health impact if causality is assumed
The attributable risk:
AR = (A/(A+B)) – (C/(C+D))
The attributable risk percentage of smoking can be calculated as:
AR % = AR / (A/(A+B)) x 100
This means 53.31% of incidence of cardiovascular disease among smokers is attributable to their smoking.
What is relative risk?
Ratio of risk of disease in the exposed to the risk in the unexposed
Relative risk = incidence in exposed / incidence in unexposed
Tells us about the strength of association between a risk factor and a disease
Relative risk of 1.74 = 74% more likely
An RR of 1.00 means that the risk of the event is identical in the exposed and control samples. An RR that is less than 1.00 means that the risk is lower in the exposed sample. An RR that is greater than 1.00 means that the risk is increased in the exposed sample.
What is relative risk reduction?
The reduction in rate of the outcome in the intervention group relative to the control group
1 minus RR
(incidence in non exposed – incidence in exposed) / incidence in non-exposed
What is absolute risk reduction?
The absolute difference in the rates of events between the 2 groups
Gives an indication of the baseline risk and the intervention effect
Incidence in nonexposed – incidence in exposed
i.e. assuming exposed means they have had a particular intervention (such as giving statins to people with hypercholesterolaemia and then a control group who do not have statins and seeing how many in each group have a heart attack to see if the intervention of statins is effective
What is number needed to treat?
the number of patients we need to treat to prevent one bad outcome
NNT = 1/(risk in non-exposed – risk in exposed)
Aka 1/absolute risk reduction
When is odds ratio used?
For case control studies it is not possible to calculate the relative risk and so the odds ratio is used.
For cross-sectional and cohort studies both can be derived but odds ratio is used if it is not clear which is the IV and which is the DV because it is symmetrical.
What is odds?
The odds of an event is the ratio of the probability of an occurrence compared to the probability of a non-occurrence.
Odds = probability/(1-probability)
eg probability = 0.75
Odds = 0.75/(1-0.75)
Odds = 3
Interpretation of odds ratio?
OR=1 Exposure does not affect odds of outcome
OR>1 Exposure associated with higher odds of outcome
OR<1 Exposure associated with lower odds of outcome
What is cumulative incidence/risk
number of new cases in a time period/ number of disease free people at the start of the time period.
Cohort study would do this
Denominator is disease-free people
It is a proportion.
Time period must be stated.
Closed population/cohort
What is incidence odds/odds of disease?
number of new cases of disease in time period/ number of people who were still disease free at the end of the time period so is probability of disease/probability of not getting disease.
Eg 25/75 if 25 out of 100 get disease. Odds of disease
calculate attributable risk and attributable risk percentage :
disease no disease
smoked 25 140
non-smoked 52 683
The attributable risk of smoking can be calculated as:
AR = (A/(A+B)) – (C/(C+D))
AR = (25/(25+140)) – (52/(52+683))
AR = .08077
The attributable risk percentage of smoking can be calculated as:
AR % = AR / (A/(A+B)) * 100
AR % = .08077 / (25/(25+140)) * 100
AR % = 53.31%
This means 53.31% of incidence of cardiovascular disease among smokers is attributable to their smoking.
What is odds ratio?
The odds ratio is the ratio of odds for exposed group to the odds for the not exposed groups.
Odds ratio = (AxD) / (BxC)
value > 1 is positive
define confidence interval
A range of values in which we are 95% certain that the true value lies
define statistical power
Statistical power is the probability of detecting an effect if there is a difference present.
More simply it means that if there was a difference in a particular factor between two groups, how likely are we to find this difference?
Power can be increased by using a greater sample size, using more precise measuring instruments, and using a higher significance value.
