1. The epidemiological tool-box
Associations – quantification using rate ratios, rate differences, odds ratios

2. Analytical epidemiology 1: Ecological Studies
The association between quantity of salt sold and oesophageal cancer mortality in counties of Henan province, China

4. Prevalence of carriers of hepatitis B surface antigen

5. Risk for cancer of the liver (cases/ population in areas of high risk for this cancer - sub Saharan Africa and eastern Asia

6. The epidemiological tool-box
Biases – information bias, selection bias
Confounding – detection and control
Determination of causation
Effect Modification/ Interaction/Synergism

7. 2*2 if only life were so simple…
Outcome Status
absent
present
exposed
Exposure Status
not exposed

8. Design of a case-control study
TIME
direction of inquiry
Exposed
Cases with disease
Unexposed
Population
Controls without disease
Exposed
Unexposed

9. Odds ratio and corresponding 95% confidence (stratified by age)
Analytical Studies 2: Case control study of Hepatitis C seropositivity and lymphoma
Odds ratio and corresponding 95% confidence (stratified by age)

10. Design of a cohort study
TIME
direction of inquiry
people exposed disease
population without the no disease
disease
not exposed disease
no disease
“at risk”

11. Analytical studies 3: Cohort of British Doctors
Death by lung cancer Current smoker Non smoker
Yes a (4,180) b (224)
No c (45,820) d (39,776)
# at beginning 50, ,000
Total ,000

12. Cohort of British Doctors cont’d
Relative risk: risk in exposed/risk in unexposed
RR = a  b = .0056 = 14.9
a+c b+d
Attributable risk = risk difference = excess risk in smokers
= = .078

13. Analytical studies 3: Shanghai - cohort study 18,000 men-synergy (Qian G-S et al, Can Epid Biom. Prev 1194;33)
Note: Aflatoxins measured by adducts, interview unreliable

14. Effect Modification (or Interaction) is said to occur when the association between exposurex and outcomey differs by variablez

15. Prevalence of Actinic keratosis in Israeli Dermatologic Patients with and without Psoriasis
51 (11%)
200 (27%)
538 (73%)
409 (89%)
Psoriatics
Controls

16. What is actinic keratosis?
Rough scaly spots on sun-damaged skin
Pre-cancerous (can give rise to Squamous cell caricnoma SCC)
Found on nose, cheeks, upper lips, temples, forehead
Common in fair-skinned people and those in outdoor occupations

17. Adjusted odds ratios (OR) for solar keratosis by hair color comparing psoriatics and controls
Adjusted for ethnic origin, gender, age and degree of sun exposure

18. Adjusted odds ratios (OR) for solar keratosis by propensity to sunburn comparing psoriatics and controls
Sometimes
Adjusted for ethnic origin, gender, age and degree of sun exposure

19. The epidemiological tool-box
Formulating study question
Gathering data
Hypothesis testing
Impact measures

20. The epidemiological tool-box
Judging the methodology
Kappa statistic & Reliability
Life Expectancy – survival analysis, life table analyses

21. The epidemiological tool-box
Measurement accuracy
N = sample size
Outcome Measures
Proportional mortality/morbidity

22. The epidemiological tool-box
Quality of data (and/or life!)
Randomization; Risk – incidence, types of incidence, incidence vs. prevalence, crude vs. disease-specific

23. The epidemiological tool-box
Standardization
Time Trends
Utility assessment
Validity
Weight of evidence

24. The epidemiological tool-box
X-axis
Y-axis and plotting the data
Z-score and statistical inference
Ж - ?????

25. Steps in Designing and Conducting an Epidemiologic Investigation
You have made an observation based on descriptive cancer statistics…….
Steps in Designing and Conducting an
Epidemiologic Investigation

26. Specify TOPIC and PURPOSE
Determining what is KNOWN and UNKNOWN
State the CASE FOR ACTION

27. - Enrico Fermi, Physicist, 1901-1954
Formulate STUDY OBJECTIVES
Formulate HYPOTHESES
“There are two possible outcomes: If the result confirms the hypothesis, then you've made a measurement. If the result is contrary to the hypothesis, then you've made a discovery”
- Enrico Fermi, Physicist,

28. Select appropriate STUDY DESIGN
Choose & define STUDY VARIABLES
Define STUDY POPULATION & SELECTION TECHNIQUES
Develop DATA COLLECTION TOOLS

29. PRETEST developed instruments
TRAIN FIELD WORKERS
CONDUCT/MONITOR FIELD WORK
Prepare data for ANALYSIS
ANALYSE the data

30. WRITE-UP findings
COMMUNICATE findings
INCORPORATE results into health planning
EVALUATE modified health program

31. It is easier to investigate problems than to solve them.
BUT…
It’s not so easy to study them either!