workshop 2 Flashcards
Morbidity: what is it and how is it measured?
“The state of being symptomatic or unhealthy for a disease or condition”
- Usually represented or estimated using prevalence or incidence
- Prevalence describes the proportion of the population with a given symptom or quality
- Incidence shows the frequency at which individuals within a specific population develop a symptom or quality
Morbidity: Prevalence being measured
Number of affected peoples/Total number of individuals within a specific population
Morbidity: Incidence being measured
Number of new cases/Number of individuals within the same population
what is mortality and how is it measured?
“the number of deaths caused
by the health event under
investigation”
• Communicated as a rate of an absolute number
• Mortality usually get
represented as a rate per 1000 individuals – also known as death rate
how is Mortality measured properly?
deaths in a given time in a given population/Total population
This number then can be multiplied by 1000 to reflect the “per 1000” rate of the target of population
what is biological plausibility?
Establishing the cause
-and-effect relationship between a biological factor and a particular disease
Establishing whether correlation means causation
what are the 8 parts of the Bradford hill Criteria?
- Strength
- Consistency
- Specificity
- Temporality
- Biological gradient
- Biological Plausibility
- Coherence
- Experiment
Bradford hill Criteria: what is strength?
(effect size) – the larger the
effect from the cause, the higher the probability of a casual link
Bradford hill Criteria: what is Consistency?
(reproducibility) – proposed causality needs to be observed in more than time point
Bradford hill Criteria: what is Specificity?
causation requires a very specific population with a very specific disease with no other possible explanations
Bradford hill Criteria: what is Temporality?
the proposed effect must occur after the cause
Bradford hill Criteria: what is Biological gradient?
dose-response effect
Bradford hill Criteria: what is Biological Plausibility?
biological mechanism between cause and effect
Bradford hill Criteria: what is Coherence?
does the cause and effect fit with what we know?
Bradford hill Criteria: what is Experiment?
does a group that lacks
exposure to the effect exhibit a difference outcome?
what’s the evidence behind BMI?
- 300,000 people WITHOUT disease were classified using their BMI
- A direct correlation between HIGHER BMI and a HIGHER risk for heart attacks, strokes, and high blood pressure
- Increase in BMI by 1 SD above the average was linked with a 13% increased risk for cardiovascular events
what are other field methods of measuring obesity?
- Waist circumference
- Waist-to-hip ratio
- Skinfold thicknesses
- Bioelectrical impedance
strengths of BMI?
Easy
Cheap
Strongly correlated with body fat levels
HUNDREDS of studies have
linked BMI as a prediction of
risk of chronic disease and
early death
weaknesses of BMI?
Doesn’t distinguish between body fat and lean mass
Cheap BMI doesn’t account for fat distribution
strengths of waist circumferences?
Easy
Cheap
Strongly correlated with body fat levels
Some studies have linked WC as a prediction of risk of chronic disease and early death
weaknesses of waist circumferences?
Its not an EXACT science, non standardized approach
Lack of good comparison
Difficult to measure in larger individuals
strengths of waist-to-hip ratio?
Strongly correlated with body fat levels
Cheap
Studies indicate a good prediction with disease and death in adults
weaknesses of waist-to-hip ratio?
Prone to error
More difficult to measure
Hard to interpret, is it due to one or the other? Lose key information
Difficult to measure in lager
individuals
strengths of skin fold thickness?
Convenient
Cheap
Safe
Fast & easy
weaknesses of skin fold thickness?
Not very accurate
Difficult to measure in lager
individuals
strengths of Bioelectrical impedance?
Convenient
Cheap (ISH)
Fast and easy
Portable
weaknesses of Bioelectrical impedance?
Hard to calibrate
Ratio of body water to fat may be change during illness, dehydration or weight loss, decreasing accuracy
Not ‘VERY’ accurate
Not very accurate at all in
bigger individuals
what are some more intense approaches?
Computerized tomography & Magnetic resonance imaging
Dual energy X-ray absorptiometry (DEXA)
Dilution Method (Hydrometric)- using isotope labelled water
Underwater Weighing (Densitometry)
Air-Displacement Plethysmography
cross sectional studies summary
- Epidemiology is based on centuries (and more!) of scientific research
- A lack of longitudinal funding means knowledge is often based on cross-sectional data
- CANNOT establish cause and effect from cross-sectional studies
- We can going to learn how this translates to policy and practice
