Changes

=='''Causation'''==

=='''Causation'''==

The ultimate aim of most analytic studies is to demonstrate evidence of a causative association between a factor of interest and a disease. Definitively establishing a causal connection between an exposure and disease is very difficult - indeed, it is considered to be impossible by philosophers<ref>Rothman, K.J. 'Causation and Causal Inference in Epidemiology', American Journal of Public Health, 2005, Vol 95, No. S1 [http://ajph.aphapublications.org/cgi/reprint/95/S1/S144]</ref>. , due to the complex interplay between different host, agent,and environmental factors, as well as many diseases being multifactorial in nature. In order to assist the investigation of causation, risk factors for disease may be classified as '''necessary''' or '''sufficient''' causes. A necessary cause is one which is required for disease to occur - i.e. it is present in every case of disease (this is commonly the case with transmissible diseases, where a pathogenic agent is often identified as the necessary cause). A

The ultimate aim of most analytic studies is to demonstrate evidence of a causative association between a factor of interest and a disease. Definitively establishing a causal connection between an exposure and disease is very difficult - indeed, it is considered to be conceptually impossible by philosophers<ref>Rothman, K.J. 'Causation and Causal Inference in Epidemiology', American Journal of Public Health, 2005, Vol 95, No. S1 [http://ajph.aphapublications.org/cgi/reprint/95/S1/S144]</ref>. , Additionally, the complex interplay between different host, agent,and environmental factors, as well as many diseases being multifactorial in nature makes the identification and interpretation of possible 'causative' factors difficult. In order to assist the investigation of causation, risk factors for disease ('''component causes''') may be classified as '''necessary''' and '''sufficient''' causes. A necessary cause is one which is required for disease to occur - i.e. it is present in every case of disease (this is commonly the case with transmissible diseases, where a pathogenic agent is often identified as the necessary cause). A sufficient cause is a combination of component causes which would result in disease.

=='''Analytic studies'''==

=='''Analytic studies'''==