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

500

various countries

Great Britain

400

Finland

300 200 100

Holland Switzerland Denmark Australia Norway Iceland Canada Sweden USA

0 0 250 500 750 1000 1250 Cigarette consumption 1500

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

50 NZ 40 USA 30 Can Den Swe UK 20 Nor Net Isr FDP Ice 10 Jam Jap Yug Fin Chi Col PR Pol Rom Hun DDP Nig 0 0

Source: Int. J. Cancer 15:617, 1975

40 80 120 160 200 240 280 320 Per capita daily meat consumption – grams

Epidemiological Methods searching for relation ships

 2.

Case-Controll or Retrospective Studies

 3.

Prospective (Cohorts-, Follow-Up-)Studies

1. Case-Controll Studies

Presence

Diseased Sample of Cases Not Diseased (Controlls) Sample of Controlls Procedure:

1.In a population identify all people with the disease in question or draw a sample of such people.

Study population

2 From the same study population an additional sample of persons without this particular disease (

controls

) is drawn.

+

Past

+ -

Exposition

1. Case-Controll Studies

Presence

Sample of cases Diseased 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..

2. From the same study population one draws a sample of persons without this disease (controls) 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.

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.

3.

4.

Examine everybody at the beginning (Exposition, Risk Factors) Observe the group over time.

Record all new diseases during the time of observation

Study Population

Presence / Basisuntersuchung

Eposed RF present Subgroup NOT SICK Prospective Observation Ø

Future

New sick 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)