1. global determinants of health Flashcards
public definition
Public = local and population measure to improve health outcomes
global definition
Global = global and international response
public and global health definition
“The art and science of preventing disease, prolonging life and promoting health through the organized efforts of society.” (Donald Acheson, 1988; WHO)
interdisciplinary
Does not just focus on medics
– Epidemiology (disease patterns, distribution across populations)
– Social sciences – psychologists
– Medicine
– Policy – laws and health policies
– Natural sciences – how transmission occurs
– + many more!
Population pyramids
—-> graph showing distribution of age groups and gender of a population
low middle income populations
LMICs (low middle income countries) have a youthful population due to
High birth rate and death rate
Low life expectancy
3 factors that determine health
• Social and economic aspects
– Income status
– Education
– Support networks
• Physical environment
– WASH – water, sanitation and hygiene practics
– Climate change
– Roads – infrastructure, road traffic accidents
• Person’s individual characteristics and behaviours
– Diet
– Smoking
– Gender (e.g. women don’t get testicular cancer)
WASH
- Safe drinking water, sanitation and hygiene
- 829,000 people each year die from unsafe drinking water, poor sanitation, hand hygiene (WHO, 2019) • Biological and chemical contamination of drinking water
WASH - infectious disease
Infectious disease risks
- Diarrhoeal disease
- NTDs – neglected tropical diseases
DALY
- DALY = years of life lost + years lived with disability
- 1 DALY = 1 year of healthy life lost
Years of healthy life lost
Every disease in the world has a disability weighting
(drawback) disability rating is based only on expert opinion
WASH and Trachoma
—> World’s leading cause of preventable blindness
Causative organis, = Chlamydia trachomatis
- ‘Disease of poverty, which goes on to breed poverty’
- Lack of clean water contributes – poor hand and face washing, transmission on fingers
- Surgery
- Antibiotics
- Face-washing = transmission
Cause inflammation of eyes
Eyelids turn inwards scratch cornea = blindness
• Environmental improvement – toilets, clean water, hygiene education
nutrition transmission definition
• Changes in pattern of diet and energy expenditure which accompany changes in economic development, lifestyle and demographics
nutrition transmission patterns 1,2,3
Pattern 1: Hunter-gatherer (in the old times)
- Pattern 2: labour intensive agriculture (interspersed with periods of famine) - pre industrial revolution
- Pattern 3: ‘receding famine’ – agriculture modernised and industrialised –
nutrition transmission pattern 4
• Pattern 4: Degenerative disease = most of the world at the moment
– Multinational control of diet.
– Most of world is here
– Diet related (non-communicable disease prevalent)
High fat, high sugar, high salt
nutrition transmission pattern 5
When people realise that pattern 4 affects health some change to pattern 5 behaviour changes = this hasn’t happened on a global or country level yet
- Pattern 5: Behavioural change -> hypothetical / anecdotal
- Conscious decision to move away from Pattern 4
- Keto diet
- Plant based
- Paleo
evidence based medicine - what is it
EBM –> evidence based medicine
Best scientific evidence
For and against
Combination of 3 factors above, equally weighted
evidence based medicine - 3 factors
Individual clinical expertise
Best external evidence
Patient values and expectations
evidence - why is it needed
- From the latter half of the 20th century: lifestyle diseases.
- Many reports in the media have caused considerable fear, confusion and reduced confidence in research.
- This appears to have grown exponentially in the SoMe social media age!
types of decision making
Driver of pressure to make evidence based decision
Use evidence to make deicsions
Focused and refined
Best used of healthcare resources
alternative to EBM approach
- Evidence
- Eminence = most qualified opinion is most important
- Vehemence
- Eloquence or elegance
- Providence
- Diffidence
- Nervousness
- Confidence
how research impacts practice
Evidence must be used to generate change in behaviour and influence clinical decision making
e.g. use of antibiotics
• Medical professionals need to be skilled in identifying the strongest evidence to support policy in a timely manner
systematic reviews
Digesting and reviewing info from lower down, controlled trials and studies
Filtered info used to determine guidelines
filterted information
Systematic reviews
Critically appraised topics
Critically appraised individual articles
Unfiltered inforamtion
Randomised control trials
Cohort studies
Case controlled studies, case series and reports
evaluating evidence
–> Reference resource where experts pool together evidence for a particular topic
- Peer-reviewed material
- Conclusion statement
- Position statement
overview of EBM
Get a good question by looking at
Popualtion – who
Intervention - what
Control group – comparison
outcome
Study design (RCT)
Do the study
How well was the study done
What do the results mean
Could they be due to chance
title
• Title – does it adequately describe the work, participants, (place), intervention/ exposure and outcome?
abstract
• Abstract – does it give a clear overview of the work, that helps answer your PICOS (other other question)?
introduction
• Introduction – remembering this is mostly the opinion of the authors. Only key point from scanning is does this go from the big picture to position the research question and justify why they did what they did?
methods
• Methods – Key part, does it make sense, can it answer their question and does it appear transparent and justify the number of participants etc.
results
• Results – The other key part, these should be logically laid out, key information in a figure, secondary data in a table. It should only be what was found and no opinions
discussion
• Discussion – As with introduction, mostly authors opinion, can be useful for first paragraph which states what the authors think the research found, and then check the conclusion is not overstated and links to the primary outcome, methods and data
questions to ask about studies
- Can I now read a paper or a review article and understand why this topic is being investigated?
- Is this an observation or an experimental study (and is it the best approach to ask this question)?
- How are the authors testing their hypotheses?
- Has the trial been registered, did the primary outcomes change? Have the number of participants been justified
- Do conclusions follow from the data presented in tables and figures?
- Are the results generalisable?
2 types of research
observational
experimental
observational research
- Establish links/associations
- Investigator takes measures but does not intervene.
- Retrospective or prospective
observational research - examples
• E.g. cross-sectional studies/surveys, case-control studies, cohort studies
Longitudinal period of time – suggest causality
experimental research
- Establish cause & effect
* An intervention is performed by the researcher, all else held constant
experimental research - examples
• E.g. intervention trials, randomised controlled trials (RCTs)reduce confounding and bias
Independent (Explanatory) variable
the explanatory or predictor variable
– the variable hypothesised to explain the outcome variable.
The cause in cause and effect
Outcome (Dependent) variable
the variable that is observed as the effect of manipulation of the independent variable.
The variable we expect to change
confounding variables
—> can’t change, residual things in population
e.g. amount of fat people eat and amount of energy, as people eat more fat = more energy
Gender
Age
Education
Control for confounding variable
• Occurs when it is not possible to disentangle the effects of two or more variables or events
accuracy/specificity
• Accuracy Closeness to the true value, also called specificity – it measures what is supposed to measure
precision/repeatability/reliability
• Precision Repeatability, also called reliability – gives same result over repeated trials
Sensitivity
The likelihood that a test will turn out positive when the result is positive
Example: % of people with clinical depression who score as “depressed” on a scale measuring depression
specificity
The likelihood that a test will turn out negative when the result is negative
Example: % of people who do not have clinical depression who score as “not depressed” on a scale measuring depression
Ideal = high specificity and high sensitivity
Can sacrifice a high sensitivity
But don’t sacrifice a high specifity as that means that you get false negatives
selection bias
Distortion, due to:
a. Methods used to select subjects
b. Factors that influence study participation
Therefore – findings represent factors determining disease AND factors determining participation
sample size
—> make sure there are enough people in the study
sample sixe and power analysis
The statistical approach to determining the sample size is a “power calculation” or “power analysis”
Typically involves accepting no more than 5 % level of error, i.e. event occurring by chance
- Sample size calculations are based on
- Level of error you will accept
- Magnitude of the effect under investigation
- Prevalence of factor you want to measure
- Relative sizes of the groups being compared
p- value
A statistical value indicating the probability that your findings are due to a real effect, and not likely to be by chance
confidence interval
A “95% C.I. (A, B)” means that if we were to repeat our experiment a very large number of times, in 95% of cases, our result would fall always between A and B.
The difference with the p-value is that the C.I. gives you a range or limits, of the lowest and highest values your result can possibly take.
Odds Ratio (OR):
A measure of how strong an effect is.
• The chance (“odds”) of an event occurring in the “control” group vs. the same event occurring in the “cases group”.
Odds Ratio (OR): values
OR = 1 means no difference between groups
OR > 1 the event is more likely in the cases = “induces” disease
OR < 1 the event is more likely in the control group = “protects
Cross sectional studies
Think of “surveys”
- Measure disease & exposure at the same time in a population
- Useful for assessing prevalence, exploring relationships & generating hypotheses
- Do not give evidence of cause & effect or change over time
- Key issues in critical appraisal include sampling, confounding & validity/reliability of methods/data
case control studies
Think of “rare diseases”
- Select “subjects” and “patients” (i.e. on basis of outcome variable, with or without disease).
- CCS look back to behaviour in the past
- Case-control studies are best for rare disease, assessment of multiple exposures
- When evaluating a case-control study consider suitability of control group and sources of bias
cohort studies
Think of “large groups” being followed over time
- Group 1 - people exposed to variable of interest
- Group 2 - people not exposed to variable of interest
- All subjects are healthy at the start of the trial except in “inception” cohorts (Greenhalgh, ch.3)
retrospective cohort
Prospective cohort – exposure measured now and in the future
retrospective cohort
Retrospective cohort - based on measurements of exposure taken in the past
Cohort studies – relative risk
All measure the risk of future outcome on the exposed group vs. on the non-exposed group
Cohort studies – relative risk values
risk if exposed/ risk if not exposed
– RR = 1 no effect of exposure
– RR > 1 the exposure increases risk
– RR <1 the exposure decreases risk
odds ratio and relative risk
• Note that the OR is a related measure to RR, it approximates to the RR
– The OR gives an estimate based on number of existing events (“cases”) now; the RR esimates a risk based on diseaese development over time
relative risk and absolute risk
RR is not absolute risk, needs changing to absolute risk, e.g. recent stories about processed meat and cancer risk (RR 17% absolute risk 1 extra case per 1000)
Effect absolute risk is different
key aspects of experimental studies
randomisation,
blinding, - do researchers know who is getting what intervention
placebo
ITT (intention to treat, do people that start the study end the study – problem with intervention may cause dropout)
• Experimental studies provide the best evidence of cause and effect – results can be used to perform meta-analyses
RCT - classic design
Study population
Define selction criteria for participsnts
Select and invite partticipants
Randomisation of participants into control and treatment groups
Complete or drop out
Experimental studies limitations
• Limitations include ethical considerations, cost and factors leading to bias
systematic reviews
• Systematic reviews are a type of Secondary Research
– Overviews primary (original) research
– Conducted following of a pre-defined, reproducible, and non-biased method (follows agreed standards)
• Systematic reviews allow a quick evaluation of the cumulative evidence behind a particular intervention
• When appraising a SR you should consider:
– Was the research question relevant and specific?
– Was the literature search conducted thorough and accurate?
– Was the quality of the studies assessed (and weighed)?
– Are conclusions reasonably deduced from the numerical results?
qualitative research
Why
Interviews, observations
Get opinions, views
Non numerical, qualitative, descriptive ?
Unrepresentative
Non statistical
quantitative research
How many, what, how
Quantified observations; interventions; laboratory
Associations; causeeffect relationships
Testing hypotheses; numerical or quantifiable
Representative
Statistical
Critical appraisal - what is it
- A process of review necessary to be able to judge the evidence
- Involves identifying both positive and negative aspects of research or evidence
- Allows to identify relevant information to enhance practice
Research process
Identify problem
Review literature
Develop testable hypothesis
Design intervention
Alect recruit subjects
Obtain and analyse data
Interpret results
Diseeminate results
What influences the quality of research
- Relevance of topic chosen when research will be finished
- Practical issues (resources, funding, staff)
- Ethical considerations
- Study design and methodology
- The play of chance (statistical analysis)
- Relevance to practice
critical analysis definition
“To weigh up the evidence critically to assess its validity (closeness to the truth) and usefulness (applicability)”. (Sackett and Haynes, 1995)
“A technique for increasing the effectiveness of your reading”
Critical analysis is not
- A description
- Making assumptions
- Making unsupported generalisation
- Not questioning the information you have
- Giving inaccurate or misleading information
- Quoting what the author’s say without giving your own views and stating the difference between the author’s opinions
why do we need to critically analyse research papers
- Information overload
- “ Science is just one of many truths”. Professor Robert Winston
- Variable quality of research
- Need for evidence-based practice
- Supports the decision-making process in clinical practice
First questions in critical analysis
- What was the research question / hypothesis?
- Why is the research needed, is it original?
- What was the study design?
- Was the study design appropriate for the question?
Methodology
• The sample
– Sample size, power of the study
– Inclusion/exclusion criteria
– Randomised, differences between groups
– Recruitment
- Intervention
- Outcome measures and measurement tools
- Duration / follow up (loss to follow up)
- Bias
Results
- Comprehensive, precision
- Bias in representation
- Presentation
- Descriptive
- Analysis
– Quantitative statistics
– Qualitative
what do you do in a critical analysis
Analyse and evaluate
– Question the information you have.
• Argue
– What is in favour of authors arguments, what is against?
- Conclude and summarise your understanding of the main points
- Develop your own view with justification
