Epidemiology in
„Sozialmedizin“
Part 2
Based in part on a powerpoint presentation by
Prof. Dr. med. Hans-Werner Hense
Translated, shortened and added to by Wirsing
Epidemiological concept: Risk factor
risk factor - any occurrence,
substance, event, change or
behaviour that increases the
probability of a particular disease
(Risk factors for CHD: smoking,
cholesterol, hypertension, diabetes)
Epidemiological Methods searching for
relationships (possible causes)
?
 1. Correlational dStudies
Two variables are (cor)related to each other
A. MORBIDITY RATES (of a given disease as incidence
or prevalence) or MORTALITY RATES WITH
B. RISK or exposure factors (as the percentage or the
mean of people exposed in the population)
-
Crude death rate for lung cancer among men in 1950
and per capita consumption of cigarettes in 1930 in
various countries
500
Great Britain
Deaths per million
400
Finland
300
Switzerland
Holland
200
USA
Denmark
Australia
Canada
Sweden
Norway
Iceland
100
0
0
250
500
750
1000
1250
1500
Cigarette consumption
Source: U.S. D.H.E.W. Smoking and Health: Report of the Advisory Committee to the Surgeon General of the Public
Health Service.
Washington, D.C.: U.S. Government Printing Office, 1964
Colon cancer incidence/100,000 women
Correlation between per capita meat consumption
and colon cancer among women in various
countries
50
NZ
40
USA
30
Can
Den
Swe
UK
20
Nor
Jam
Net
Isr
Fin
PR
Pol
Yug
Chi
Jap
Rom
Hun
Col
Nig
10
0
0
40
80
120
160
FDP
Ice
DDP
200
240
280
320
Per capita daily meat consumption – grams
Source: Int. J. Cancer 15:617, 1975
Epidemiological Methods searching for relationships
2.Case-Controll or Retrospective Studies
3. Prospective (Cohorts-, Follow-Up-)Studies
1. Case-Controll
Studies
Presence
Sample of
Cases
Diseased
Not Diseased
(Controlls)
Sample of
Controlls
Procedure:
Study population
1.In a population identify all people with
the disease in question or draw a sample
of such people.
2 From the same study population an additional sample
of persons without this particular disease (controls) is drawn.
1. Case-Controll Studies
Past
Presence
Sample of
cases
-
+
Diseased
Exposition
+
-
Not Diseased
(Controls)
Sample of
controls
Procedure:
Study population
1.All (or a sample of ) people with the disease in question
(i.e. all cases) from a clearly defined study population are
identified..
3. Die Exposition in der Vergangenheit
gegenüber potentiellen Risikofaktoren
wird ermittelt.
2. From the same study population one draws a sample
of persons without this disease (controls)
4.Die Häufigkeit von Risikofaktoren unter
den so definierten Fällen und Kontrollen
wird dann mit geeigneten Methoden
miteinander verglichen.
See also:
http://documentaryheaven.c
om/the-tobacco-conspiracy/
This study from 1950 was done by means of a case control study and
showed that heavy smokers are more likely to get lung cancer than no or
light smokers
From the study
done by Doll et
al. in 1950
Prospectiv- or Cohortstudies
1.
Select a group of people from the general population that does not suffer
from the disease to be investigated.
2.
Examine everybody at the beginning (Exposition, Risk Factors)
3.
4.
Observe the group over time.
Record all new diseases during the time of observation
Future
Presence / Basisuntersuchung
Study Population
Eposed
RF present
Subgroup
NOT SICK
Ø
New
sick
Prospective Observation
Not exposed RF
Not present
Ø
New
sick
Prospective- or Cohortstudies
Definition of Relative Risk of a risk factor (RF) or exposition
The Relativ Risk is the proportion of the incidence rate of exposed
people divided by the same rate of non-exposed people
Or: the incidence rate of people with the risk factor relative to people
without the risk factor
Incidence rate of the exposed / with RF
RR = --------------------------------------------------------------Incidence rate of the non- exposed / without RF
RR > 1.0 : Exposition / RF leads to more disease
RR = 1.0 : Exposition / RF has no influence on disease
RR < 1.0 : Exposition / PF protects from disease
The Relative Risk ist a measure of the extent to which an exposition or
a risk factor is likely to make you sick or has an preventive effect
Epidemiological Models that try to account for for
infectious diseases (Koch’s Model)
Parts (Dimensions) of Koch’s Model: Host (“Wirt”)
The person susceptible to the Agent plus
Factors, such as
• immune status from previous lived through
infections
• gender • marital status • occupation
• socio-economic position • diet (malnourished ?)
• behaviour of the host which allows the
transmission of the agent: mingling in crowds of
people, spreading aerosolized droplets by
sneezing, coughing, kissing; engaging in
unprotected sex with many partners; ingesting
fecally contaminated water or food; getting in
contact with contaminated inanimate material by
handling it without washing hands or by stepping
on it with naked feet, defecating in or close to
open waters, bathing in contaminated waters.
Parts (Dimensions) of Koch’s Model: Agent (“Agens”)
The biological agent that is necessary – but
not necessarily sufficient - to cause the
corresponding infection (bacteria, virus,
helminth [worms], protozoa, fungi, toxins)
Source: en.wikipedia.org—
Infectious_disease
The most mortal infectious diseases
worldwide for children are: Diarrhea
(bacteria, viruses, toxins and protozoa),
Malaria (a protozoa), Measles (virus),
Pertussis (bacteria), Polio (virus), Diphteria
(bacteria), Lower Respiratory Infections
(most of them viruses).
Parts (Dimensions) of Koch’s Model: Vector (“Vektor”)
Vector (the mechanical [flies] or biological
transmitters [mosquitos, snails, bugs, ticks, also
called intermediate hosts] of the Agent. Vectors are
not always involved in transmission, unless you
also want to consider infected humans as “vectors”
Parts (Dimensions) of Koch’s Model: Environment (“Umwelt”)
Environment of Host which supports the survival of Agent
and Vector and the unhealthy behaviour of the Host: the
natural (weather, temperatures, earthquakes, tsunamis)
and man-made environment (deforestation, air pollution,
monocultures, lack of drinkable water, no separation of
drinking water and sewage, housing which allows the entry
of bugs and mosquitos), the political system (dictatorship,
internal and external wars, corruption, forced displacement
of people), demographic conditions (number of already
infected and susceptible persons), socio- economic
conditions (inequality, poverty, developing country, small or
non-existent health budget)
To what extent has the political
ENVIRONMENT in
e.g. Congo, Burma or Colombia,
characterized by
war,
political oppression, violation of
human rights
led to the resurgence of nearly
forgotten infectious
diseases?
EVIDENCE is mounting for associations between increased
prevalence of neglected tropical infectious diseases ....
such as: protozoan infections, helminths, and other diseases
such as leprosy and trachoma, that are prevalent in the worldʼs least
developed nations.
Neglected protozoan infections include leishmaniasis, Chagas disease
and African trypanosomiasis.
Helminth infections include lymphatic filariasis, ascariasis,
onchocerciasis, dracunculiasis, and schistosomiasis.
... and the conflict and systematic violation of human rights.
At-risk populations in these countries have limited access to
preventive and curative services, Military forces have
interrupted access of civilians to essential medicines
CONGO: the re-emergence of African
trypanosomiasis as a result of civil war in the
Democratic Republic of the Congo
BURMA: The eastern frontiers of Burma are
mostly inhabited by ethnic minority groups who
have been engaged in civil war with the
Burmese military regime for more than 40
years. Civilians were forcibly displaced, used for
forced labour, extorted, and often killed to
terrorise the population and reduce support for
ethnic insurgents. This has led to a high
prevalence of many infectious diseases
including HIV, multidrug-resistant tuberculosis,
malaria, and lymphatic filariasis
COLOMIA:
Political violence escalated in the 1980s.
Guerrilla organisations and so-called self-defense
paramilitary groups.
They sustain themselves financially by kidnapping people
and by cocaine production, trafficking, and export
Led to isplacement of about 3,3 million people between
1985 and 2005
Diseases affecting the Colombian conflict zones include
Chagasʼ disease (American trypanosomiasis),
leishmaniasis, and yellow fever
FROM: Beyrer Chris , Juan Carlos Villar, Voravit Suwanvanichkij, Sonal
Singh, Stefan D Baral, Edward J Mills (2007). Neglected diseases, civil
conflicts, and the right to health. www.thelancet.com Vol 370 August 18,
2007: 619-627
Risky socio-‐structural aspects
Industrialized societies: Individualism with few sources of
social capital and support, individual and institutional racism
and discrimination towards ethnic minorities, laws limiting
access to medical system for some groups, exploitation of
workers, high rate of un‐ and underemployment, inadequate
housing or homelessness, dangerous working conditions, air
pollution and dangers from nuclear accidents, domestic and
other violence, crowding and stressful working and living
conditions; easy availability of cigarettes, firearms, drugs,
and alcohol; limited access to healthy foods but easy access
to highly advertised junk foods, little opportunity for physical
activity; ineffective health education, high social inequality
and high rate of poverty, war, social disorganisation,
mistakes caused by the medical profession (iatrogenic
causes of disease)