The BMJ style from June 2024 has inline citations in brackets. However, current papers at the BMJ have inline citations in superscript (https://www.bmj.com/content/390/bmj-2024-083978). Curiously, their website at https://www.bmj.com/about-bmj/resources-authors/house-style says nothing about formatting inline citations.

So maybe leave as is with inline brackets?