RESUMO
BACKGROUND AND OBJECTIVE: Inadequate competing interest declarations present interpretive challenges for editors, reviewers, and readers. We systematically studied a common euphemism, 'unpaid consultant,' to determine its occurrence in declarations and its association with vested interests, authors, and journals. METHODS: We used Google Scholar, a search engine that routinely includes disclosures, to identify 1164 occurrences and 787 unique biomedical journal publications between 1994 and 2014 that included one or more authors declaring themselves as an "unpaid consultant." Changes over time were reckoned with absolute and relative yearly rates, the latter normalized by overall biomedical publication volumes. We further analyzed declarations according to author, consultancy recipient, and journal. RESULTS: We demonstrate increases in the use of "unpaid consultant" since 2004 and show that such uninformative declarations are overwhelmingly (801/865, 92.6%) associated with for-profit companies and other vested interests, most notably in the pharmaceutical, device, and biotech industries. CONCLUSIONS: Disclosing 'unpaid' relationships with for-profit companies typically signals but does not explain competing interests. Our findings challenge editors to respond to the increasing use of language that may conceal rather than illuminate conflicts of interest.