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Health News Archive 726 - Study Bias
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Funding Source Bias Regarding Adverse Effects

Studies of inhaled corticosteroids, medications frequently prescribed for asthma and other respiratory problems, appear less likely to find adverse effects if they are funded by pharmaceutical companies than if they are funded by other sources, according to a report in the October 22, 2007 issue of Archives of Internal Medicine, one of the JAMA/Archives journals.

“Inhaled corticosteroids are considered the cornerstone treatment for inflammatory respiratory diseases, especially asthma, even in mild or moderate cases,” the authors write as background information in the article. “However, they are not free of adverse effects, and concerns have been raised about long-term treatment courses in milder cases of disease or in young children.” Their use has been associated with potentially harmful decreases in the stress hormone cortisol, decreases in bone mineral density and growth suppression.

Antonio Nieto, M.D., Ph.D., of the Children’s Hospital La Fe, Valencia, Spain, and colleagues assessed the safety reporting of inhaled corticosteroids in 504 studies of the drugs published between 1993 and 2002. Of those, 275 were funded by pharmaceutical companies and 229 were funded by other sources, including non-profit organizations and government agencies.

Overall, 34.5 percent of pharmaceutical-funded studies and 65.1 percent of studies with other funding sources found a significant difference in adverse effects between individuals assigned to inhaled corticosteroid groups and those who were not. This difference was no longer statistically significant when the researchers factored in components of the study design, such as dosage amounts or a focus limited to certain adverse effects, suggesting that the association between funding source and more positive outcomes may result from variations in study design.

“Remarkably, type of funding was a major determinant of the authors’ interpretation of the adverse effects,” the authors write. In studies that did find a significant association between corticosteroids and adverse effects, authors of manufacturer-funded studies were more likely to conclude the drugs were safe than authors of studies with no pharmaceutical funding.

Because the interpretations are subjective, it is difficult to determine if studies funded by the manufacturer are too positive or studies with no pharmaceutical funding are too cautious, the authors note. “However, we postulate that having information on source of funding will help readers of these studies have a better informed and balanced judgment on the authors’ interpretations,” they conclude. “Disclosure of conflicts of interest should be strengthened for a more balanced opinion on the safety of drugs.”

Source: Press Release Oct 22, 2007 American Medical Association (AMA)

Arch Intern Med. 2007;167(19):2047-2053.

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