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)