April 25, 2012. We added to Bradford Hill Criteria of Causation: (b) Confounding. One thing to look out for is when two effects both occur at the same time so that you cannot know which was the real cause. This situation is called confounding. For example, since the main source of lycopenes is tomato products if one found that consumption of tomato products reduced the risk of prostate cancer one could never be quite sure if the reason was due to lycopenes or due to something else in the tomato or even due to something else that is typically eaten with tomato. For example, tomato is a common component of pizza and there is some test tube evidence that the carvacrol component of oregano may have an anti-cancer effect. The anti-cancer effect being hypothesized for lycopenes may actually be due to oregano (See [Science Daily]).
April 8, 2012. We added to Bradford Hill Criteria of Causation: Another example where adjustment was crucial was a study on health care workers who were accidentally pricked with HIV needles. Those treated with AZT (a medicine for HIV) fared no better than those who were not so treated; however, when adjustment was made for the severity of the needle prick then AZT administration was observed to have a beneficial effect. Had this adjustment not been made a potentially life saving treatment might have been overlooked. See the Neuroskeptic Blog and [PMID: 9366579] [Full Free Text].
April 8, 2012. We added to Bradford Hill Criteria of Causation: Unfortunately lack of reproducibility can be a problem as reported on the [Science Exchange blog]: "Amgen found that 47 of 53 "landmark" oncology publications could not be reproduced. Bayer found that 43 of 67 oncology and cardiovascular projects were based on contradictory results from academic publications. Dr. John Ioannidis and his colleagues found that of 432 publications purporting sex differences in hypertension, multiple sclerosis, or lung cancer, only one data set was reproducible."
April 2, 2012. We added to Bradford Hill Criteria of Causation: Yet another problem to be aware of are situations where the control treatment has a beneficial or detrimental effect. For example, researchers have hypothesized that the control treatment in the Provenge trials actually harmed the patients which would make the Provenge arm of the trial seem better than it really was. See [News]
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