Why should medical students be interested in

EPIDEMIOLOGY?

Very basic concepts

What is EPIDEMIOLOGY?Epidemiology is the study of the distribution a

nd determinants of health-related states or events in specified populations, and the application of this study to control of health problems.

Last ed. Dictionary of Epidemiology

But can you imagine what is epidemiology like in clinical practiceby reading definition?

Let's see some examples

First, I will show you observational data of mortality.

Mortality in Area A and Area B

Area A Area B

dead/population

500/10,000 1000/10,000

mortality 5% 10%

If you categorize the populations by age and compare mortality of Area A

with that of Area B

area A area B

age<60dead/

population

500/10,000 250/5,000

mortality 5% 5%

60=<agedead/

population

0/0 750/5,000

mortality - 15%

The factors should be taken into consideration when you look at the data.

age sex race year of birth .

Answer

CDC revised classification system for HIV (AIDS) infection in 1993

Next example subjects:

smokers: 1000 non smokers: 1000 of same age range, sex ratio

status of lung cancer for 5 years were observed.

Results in 5 years

smokersnon

smokers

lung cancer/ 1,000

50/1,000 10/1,000

morbidity 5% 1%

If the sample size of both group is not 1,000, but

100.

smokersnot

smokers

lung cancer/ total

5/100 1/100

morbidity 5% 1%

Next example

lung cancer healthy

alcohol intake yes/

no71/29 52/48

yes/no ratio 2.45 1.08

p=0.006 by Chi-square test

Non-smokers

lung cancer healthy

alcohol intake yes/

no8/22 16/44

yes/no ratio 0.36 0.36

p=1.0 by Chi-square test

Smokers

lung cancer healthy

alcohol intake yes/

no63/7 36/4

yes/no ratio 9 9

p=1.0 by Chi-square test

Why should medical students beinterested in

EPIDEMIOLOGY?

Welcome to the world of Epidemiology