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. 2022 Sep 19;12(9):e063501. doi: 10.1136/bmjopen-2022-063501

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© Author(s) (or their employer(s)) 2022. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.

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Variable types by year number (1986–2021). Figure includes number of studies per year by dependent variable (DV) type (A), number of studies by independent variable (IV) type for studies assessing industry funding (B) and number of studies by IV type for studies evaluating COI (C). COI, conflicts of interest.