Bradford Hill has listed nine aspects concerned with the association between exposure and disease which need to be considered. The first of these is the strength of the association. A strongly elevated relative risk is more likely to reflect a causal association than is a slightly or moderately increased risk. Consistency of findings across studies conducted with different methodologies and in different settings, is another aspect. A third characteristic is specificity, that the exposure causes a particular disease, e.g. the observation that cigarette smoking is associated with squamous cell carcinoma of the respiratory tract. An important condition is the Sequence of events: the potentially causative factor must precede the effect, which in this context is disease. The dose-response relationship, or biological gradient, is another aspect. For example, massive exposure to sunlight is more likely to cause melanoma in susceptible individuals than is little or moderate sunlight. Biological plausibility is an aspect which is important, but depends on the biological knowledge of the day. The association should be consistent with what is generally known about the occurrence of the disease, its natural history and pathophysiology, and should not conflict with this knowledge. The causal interpretation of an association is furthered if there is experimental evidence in support of it, for example if elimination of exposure reduces the incidence of the disease. The ninth aspect is analogy. For example, if a virus is shown to be oncogenic in animal studies, we are more prone to accept that the human papilloma virus may be the cause of cervical cancer in humans. In his essay on association and causation, Bradford Hill notes that " none of my nine viewpoints can bring indisputable evidence for or against the cause-and-effect hypothesis and none can be required as a sine qua non ". The challenge of assessing causation is one of many fascinating aspects of epidemiological research.
Assuming you establish causality, how do you go for estimating much of the morbidity and mortality from a disease, for instance, might be prevented by interventions? Just curious, yanno
Back to the subject Copyright issues have traditionally been not given the importance they deserve. That's have been the case even in the US, let alone in less developed countries. When I was in school in Russia I remember many professiors who'd translate books from English to Russian and publish it as if they had written it themselves, under their own name. We as students would not mind it had the books been translated correctly.. but these "professors" did not even know English good enough! Believe it or not, in British law publishing someone else's original copy work and claiming you have made it (known as plagiarism and completely different from copyright infringement) is a criminal offence. For the most part, the criminal law is only used for commercial copyright infringement with one exception, and an offence is committed when knowing or reasonably suspecting that the files are illegal copies, and without the permission of the copyright owner, a person:makes unauthorised copies e.g. burning music files or films on to CD-Rs or DVD-Rs;distributes, sells or hires out unauthorised copies of CDs, VCDs and DVDs;on a larger scale, distributes unauthorised copies as a commercial enterprise on the internet;possesses unauthorised copies with a view to distributing, selling or hiring these to other people;while not dealing commercially, distributes unauthorised copies of software packages, books, music, games, and films on such a scale as to have a measurable impact on the copyright owner's business;publishing someone else's original copy work and claiming you have made itcertain copyrights allow Archival copies of software to be made however these are not to be distributed. The penalties for these "copyright infringement" offences depend on the seriousness of the offences:before a magistrates' Court, the penalties for distributing unauthorised files are a maximum fine of £5,000 and/or six months imprisonment;in the Crown Court, the penalties for distributing unauthorised files are an unlimited fine and/or up to 10 years imprisonment. Also note §24 Copyright and Related Rights Regulations 2003 which creates a range of offences relating to the distribution of any device, product or component which is primarily designed, produced, or adapted for the purpose of enabling or facilitating the circumvention of effective technological measures. When this is for non-commercial purposes, it requires there to be a measurable effect on the rights holder's business.
[...] from both cohort and case-control studies always reflect true associations which can be universally generalized. Epidemiological research is, to a large extent, of an observational character as opposed to experimental research. One should not forget that observational epidemiological studies are subject to the influence of factors over which the investigators most often do not have full control, and that findings from these studies are less reliable than those of studies with an experimental research design. It is therefore imperative that findings from analytical epidemiological studies are critically scrutinized before any judgement of causality is made. Furthermore, findings from one single epidemiological study only exceptionally provide conclusive evidence of a causal relationship between exposure and disease.
Page created in 0.707 seconds with 19 queries.