workshop 2

Question 1

Morbidity: what is it and how is it measured?

Answer 1

“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

Question 2

Morbidity: Prevalence being measured

Answer 2

Number of affected peoples/Total number of individuals within a specific population

Question 3

Morbidity: Incidence being measured

Answer 3

Number of new cases/Number of individuals within the same population

Question 4

what is mortality and how is it measured?

Answer 4

“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

Question 5

how is Mortality measured properly?

Answer 5

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

Question 6

what is biological plausibility?

Answer 6

Establishing the cause
-and-effect relationship between a biological factor and a particular disease
Establishing whether correlation means causation

Question 7

what are the 8 parts of the Bradford hill Criteria?

Answer 7

1. Strength
2. Consistency
3. Specificity
4. Temporality
5. Biological gradient
6. Biological Plausibility
7. Coherence
8. Experiment

Question 8

Bradford hill Criteria: what is strength?

Answer 8

(effect size) – the larger the

effect from the cause, the higher the probability of a casual link

Question 9

Bradford hill Criteria: what is Consistency?

Answer 9

(reproducibility) – proposed causality needs to be observed in more than time point

Question 10

Bradford hill Criteria: what is Specificity?

Answer 10

causation requires a very specific population with a very specific disease with no other possible explanations

Question 11

Bradford hill Criteria: what is Temporality?

Answer 11

the proposed effect must occur after the cause

Question 12

Bradford hill Criteria: what is Biological gradient?

Answer 12

dose-response effect

Question 13

Bradford hill Criteria: what is Biological Plausibility?

Answer 13

biological mechanism between cause and effect

Question 14

Bradford hill Criteria: what is Coherence?

Answer 14

does the cause and effect fit with what we know?

Question 15

Bradford hill Criteria: what is Experiment?

Answer 15

does a group that lacks

exposure to the effect exhibit a difference outcome?

Question 16

what’s the evidence behind BMI?

Answer 16

• 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

Question 17

what are other field methods of measuring obesity?

Answer 17

• Waist circumference
• Waist-to-hip ratio
• Skinfold thicknesses
• Bioelectrical impedance

Question 18

strengths of BMI?

Answer 18

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

Question 19

weaknesses of BMI?

Answer 19

Doesn’t distinguish between body fat and lean mass

Cheap BMI doesn’t account for fat distribution

Question 20

strengths of waist circumferences?

Answer 20

Easy

Cheap

Strongly correlated with body fat levels

Some studies have linked WC as a prediction of risk of chronic disease and early death

Question 21

weaknesses of waist circumferences?

Answer 21

Its not an EXACT science, non standardized approach

Lack of good comparison

Difficult to measure in larger individuals

Question 22

strengths of waist-to-hip ratio?

Answer 22

Strongly correlated with body fat levels

Cheap

Studies indicate a good prediction with disease and death in adults

Question 23

weaknesses of waist-to-hip ratio?

Answer 23

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

Question 24

strengths of skin fold thickness?

Answer 24

Convenient

Cheap

Safe

Fast & easy

Question 25

weaknesses of skin fold thickness?

Answer 25

Not very accurate

Difficult to measure in lager
individuals

Question 26

strengths of Bioelectrical impedance?

Answer 26

Convenient

Cheap (ISH)

Fast and easy

Portable

Question 27

weaknesses of Bioelectrical impedance?

Answer 27

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

Question 28

what are some more intense approaches?

Answer 28

Computerized tomography & Magnetic resonance imaging

Dual energy X-ray absorptiometry (DEXA)

Dilution Method (Hydrometric)- using isotope labelled water

Underwater Weighing (Densitometry)

Air-Displacement Plethysmography

Question 29

cross sectional studies summary

Answer 29

• 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