Epidemiology

Question 1

Prevalence

Answer 1

Number of EXISTING cases of an outcome at ONE POINT IN TIME

expressed as proportion or percentage

Question 2

Incidence

Answer 2

Number of NEW cases of an outcome DURING A TIME INTERVAL

expressed as rate (denominator includes time component)

Question 3

Risk

Answer 3

Probability of disease occurring in a disease-free population during a specified time period
Risk = N/P
N = new cases in defined period
P = population at risk

Question 4

Rate

Answer 4

Probability of disease occurring in a disease-free population during the sum of individual follow up periods (person-time)
Rate = N/T
N = new cases in defined period
T = total person-time of follow-up

Question 5

Relative Risk (RR)

Answer 5

RELATIVE change in risk/rate of outcome associated with exposure
RR = Re/Ru
Re= Risk/Rate among exposed
Ru = Risk/Rate among unexposed

Question 6

Attributable Risk (AR)

Answer 6

ABSOLUTE change in risk/rate of outcome associated with exposure
AR = Re – Ru
Re= Risk/Rate among exposed
Ru = Risk/Rate among unexposed

Question 7

Attributable Risk Percent (AR%)

Answer 7

AR% = [(Re – Ru) / Re ] * 100

Question 8

Population Attributable Risk (PAR)

Answer 8

PAR = Rt – Ru
Rt = Risk/Rate in whole population (both exposed and unexposed)
Ru = Risk/Rate among unexposed

Question 9

Population Attributable Risk Percent (PAR%)

Answer 9

PAR% = [ (Rt – Ru) / Rt ] * 100
Rt = Risk/Rate in whole population (both exposed and unexposed)
Ru = Risk/Rate among unexposed

Question 10

Bradford Hill Criteria for Causality

Answer 10

Temporal Relationship
Strength
Dose Relationship
Consistency (multiple studies show same results)
Plausibility (makes sense)
Excludes Alternatives
Experimental Evidence
Specificity (lung cancer & smoking study)
Coherence

Question 11

Odds Ratio

Answer 11

Used for case control studies to approximate relative risk

OR = odds of exposure vs non exposure among cases / odds of exposure vs non exposure among controls

Question 12

Hazard

Answer 12

Continuously updated instantaneous rate
Week 1, 10 die, hazard week 1 = 10/1000
Week 2, 15 die, hazard week 2 = 15/990

Question 13

Relative Rate Reduction

Answer 13

Relative Rate Reduction = Rc / Ri
Rc = rate of outcome in control arm
Ri = rate of outcome in intervention arm

Question 14

Absolute Rate Reduction

Answer 14

Absolute Rate Reduction = Rc – Ri
Rc = rate of outcome in control arm
Ri = rate of outcome in intervention arm

Question 15

Number Needed To Treat

Answer 15

NNT = 1 / (absolute risk or rate reduction)

Defines number of people needed to undergo the intervention in order to prevent outcome in one person

Question 16

PICOT

Answer 16

Population
Intervention
Comparator/Control
Outcome
Timing

Question 17

Internal Validity

Answer 17

Extent to which the results of a study are valid (accurate, robust, sound and complete).

Question 18

Statistical Significance

Answer 18

P-value < 0.05

Probability that the observed result arose from chance

Question 19

Confidence Interval

Answer 19

Interval within there is 95% chance the true value lies

If null value is excluded result is statistically significant

Question 20

External Validity

Answer 20

Extent to which the results of a study are applicable to a clinical scenario (using PICOT)

Question 21

Systematic Review

Answer 21

Idenitify, appraise,select, synthesize
Focuses on single question
Well defined criteria
Highest NHMRC level of evidence

Question 22

Meta-analysis

Answer 22

Statistical Aspect of systematic review
Derived (weighted-average) effect size
Increases power and answers other questions

Question 23

Heterogeneity

Answer 23

Whether component studies are similar enough to be pooled

Question 24

Diagnostic Test

Answer 24

Confirmation of disease (high pre-test probability of disease)

Question 25

Screening test

Answer 25

Identify patients who may have disease (low pre-test probability of disease)

Question 26

Sensitivity

Answer 26

True Positive / (True Positive + False Negative) | % of people with disease that test positive

Question 27

Specificity

Answer 27

True Negative / (True Negative + False Positive) | % of people without disease that test negative

Question 28

Positive Predictive Value

Answer 28

True Positive / (True Positive + False Positive) % of positive tests that are truly positive Dependant on prevalence of disease

Question 29

Negative Predictive Value

Answer 29

True Negative / (True Negative + False Negative) % of negative tests that are truly negative Dependant on prevalence of disease

Question 30

Likelihood Ratio of Positive Test

Answer 30

Sensitivity / (1 - Specificity)

Question 31

Likelihood Ratio of Negative Test

Answer 31

(1 - Sensitivity) / Specificity)

Question 32

Social Determinants of Health

Answer 32

1. Social Gradient 2. Stress 3. Early Start 4. Social Inclusion 5. Work 6. Unemployment 7. Social Support 8. Addiction 9. Food 10. Clean Transport

Question 33

Observational Studies

Answer 33

``` case series, case reports ecological cross-sectional case-control cohort ```

Question 34

Interventional Studies

Answer 34

clinical trials

Question 35

Descriptive Studies

Answer 35

case series, case reports ecological cross-sectional e.g. How common is coronary heart disease?

Question 36

Analytical Studies

Answer 36

case-control cohort clinical trials e.g. Does dyslypidaemia increase the risk of CHD? Do lipid-lowering medications decrease the risk of CHD?

Question 37

Cross Sectional Studies

Answer 37

``` Data collected via questionnaires, examinations, investigations Mostly descriptive (esp. PREVALENCE) ```

Question 38

Case Control Studies

Answer 38

``` Comparison of PREVIOUS exposure between Cases (have outcome) and Controls (without outcome) Matched by confounders RETROSPECTIVE Useful for studying rare outcomes output: ODDS RATIO ```

Question 39

Cohort Studies

Answer 39

LONGITUDINAL with FOLLOW-UP collect INCIDENCE data derive RELATIVE RISKS

Question 40

Clinical Trials

Answer 40

``` LONGITUDINAL assess if INTERVENTION changes INCIDENCE outcomes: RR HR ARR NNT ```

Question 41

Death Stats

Answer 41

1/5 deaths are children under 5 - communicable diseases account for 50% - malnutrition underlying cause of 30% - 37% of deaths are neonates (under 28 days) out of every 10 deaths - 6 non-communicable diseases - 3 communicable, reproductive, nutritional - 1 injury (males) Leading causes of death - Ischemic Heart Disease - Cardiovascular Disease - Infections / Parasitic - Cancers

Question 42

Millenium Development Goal 4

Answer 42

Reduce the under 5 mortality rate by 2/3rds by 2015

Question 43

Leading Global Cause of DALYs

Answer 43

- Unipolar depressive disorders - Hearing loss (adult onset) - Alcohol use disorders

Question 44

Leading global risk factors for mortality

Answer 44

- High Blood Pressure (13% of deaths) - Childhood underweight (2million children) - Unsafe water, sanitation, hygiene, indoor smoke (2million children) - Unsafe sex - Tobacco (1/8 deaths over 30) - Obesity (7% of deaths globally)

Question 45

Tobacco Control

Answer 45

Tobacco is a risk factor for 6 of the top 8 leading causes of death Monitor tobacco use and prevention policies Protect people from tobacco smoke (smoking bans) Offer help to quit tobacco use (nicotine replacement) Warn about the dangers of tobacco (packaging & adds) Enforce bans on tobacco advertising Raise taxes on tobacco (most effective) Australia most expensive place to buy Marlboro Tobacco use declining among teens (alcohol rising) Lung cancer rates declining in males (females rising) COPD death rates declining CHD rates declining 400,000 deaths averted ``` Tobacco will kill approx 1billion people this century (due to smoking by pre-teens in south east asia and china WHO FCTC (framework convention on tobacco control) developed to combat worldwide tobacco smoking ```

Question 46

Leading causes of Blindness and Vision Impairment

Answer 46

Blindness (Australia) - Age Related Macular Degeneration (48%) - Glaucoma (14%) - Cataract (12%) Vision Impairment (Australia) - Refractive Error (62%) - Cataract (14%) - Age Related Macular Degeneration (10%) Blindness (Worldwide) - Cataract (39%) - Refractive Errors (18%) - Glaucoma (10%)

Question 47

Indigenous Eye Health

Answer 47

Aboriginal kids born with better vision (1/5th vision loss c.f mainstream) Blindness 6x more common in adults than mainstream Low vision 3x more common Primary causes - Cataract (12x more common, 7 year wait for surgery) - Refractive Errors (only 20% wear glasses) - Trachoma (Surgery, Antibiotics, Facial cleanliness, Environmental improvements) - Diabetes (only 20% have yearly eye exam) 94% of vision impairment avoidable with early intervention