Transcript Epi2
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)