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. 2022 Jun 3;12(6):e045115. doi: 10.1136/bmjopen-2020-045115

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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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Timing of available online of included studies*. The numbers of primary studies and systematic reviews for May 21 are higher because the literature search ended at 15 May 2021.