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Epidemiology in
„Sozialmedizin“Part 2
Based in part on a powerpoint presentation by Prof. Dr. med. Hans-Werner HenseTranslated, 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 Epidemiological Methods searching for relationships (possible causes)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
0
100
200
300
400
500
0 250 500 750 1000 1250 1500
Great Britain
Switzerland
Finland
USAHolland
DenmarkAustralia
CanadaSwedenNorway
Iceland
Cigarette consumption
Dea
ths
per
mil
lio
n
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
Correlation between per capita meat consumption and colon cancer among women in various
countries
0
10
20
30
40
50
0 40 80 120 160 200 240 280 320
Per capita daily meat consumption – grams
Co
lon
can
cer
inci
den
ce/1
00,0
00 w
om
en
Source: Int. J. Cancer 15:617, 1975
Nig
USA
NZ
Jam
YugChi
ColJap
Den
UK
Can
Nor IsrNet
DDP
Ice
FDP
Swe
Hun
PolPR
Rom
Fin
Epidemiological Methods searching for relation-Epidemiological Methods searching for relation-shipsships
2.Case-Controll or Retrospective Studies
3. Prospective (Cohorts-, Follow-Up-)Studies
Study population
Diseased
Not Diseased(Controlls)
1. Case-Controll 1. Case-Controll StudiesStudies
Procedure:
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.
PresenceSample ofCases
Sample ofControlls
Diseased
Not Diseased(Controls)
Study population
1. Case-Controll Studies1. Case-Controll Studies
Procedure:
1.All (or a sample of ) people with the disease in question (i.e. all cases) from a clearly defined study population are identified..
2. From the same study population one draws a sample of persons without this disease (controls)
Past Presence
+ -
3. Die Exposition in der Vergangenheit gegenüber potentiellen Risikofaktoren wird ermittelt.
4.Die Häufigkeit von Risikofaktoren unter den so definierten Fällen und Kontrollen wird dann mit geeigneten Methoden miteinander verglichen.
+ -
Exposition
Sample ofcontrols
Sample ofcases
See also: http://documentaryheaven.com/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
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 CohortstudiesProspectiv- or Cohortstudies
1. Select a group of people from the general population that does not suffer from the disease to be investigated.
ØNew sick
ØNew sick
Presence / Basisuntersuchung Future
Prospective Observation
EposedRF present
Not exposed RFNot present
Study Population
SubgroupNOT SICK
2. Examine everybody at the beginning (Exposition, Risk Factors)
3. Observe the group over time.4. Record all new diseases during the time of observation
Prospective- or CohortstudiesProspective- or Cohortstudies
Definition of Relative Risk of a risk factor (RF) or expositionDefinition 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 RFRR = ---------------------------------------------------------------
Incidence rate of the non- exposed / without RF
RR > 1.0 : Exposition / RF leads to more diseaseRR = 1.0 : Exposition / RF has no influence on diseaseRR < 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 Epidemiological Models that try to account for for infectious diseases (Koch’s Model)infectious diseases (Koch’s Model)
Parts (Dimensions) of Koch’s Model: Host (“Wirt”)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”)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”)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”)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 rightsled to the resurgence of nearly
forgotten infectiousdiseases?
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 Africantrypanosomiasis as a result of civil war in the
Democratic Republic of the Congo
BURMA: The eastern frontiers of Burma aremostly inhabited by ethnic minority groups who
have been engaged in civil war with theBurmese military regime for more than 40
years. Civilians were forcibly displaced, used forforced labour, extorted, and often killed to
terrorise the population and reduce support forethnic insurgents. This has led to a highprevalence 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, SonalSingh, Stefan D Baral, Edward J Mills (2007). Neglected diseases, civilconflicts, 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)