A long standing question is to what extent restricting the language choice to English makes much difference. In this post we highlight four articles that tackle this issue. Three of the four found it made minimal difference while the fourth (by far the oldest) suggested it may cause a bias. There is now another paper to be added to the discussion:

Restricting evidence syntheses of interventions to English-language publications is a viable methodological shortcut for most medical topics: a systematic review: Excluding English-language publications a valid shortcut Dobrescu et al. Journal of Clinical Epidemiology (2021)

This concludes: “Restricting systematic reviews to English-language publications appears to have little impact on the effect estimates and conclusions of systematic reviews.“

While my 5 articles have not been found via any rigorous search the references from this paper contain a number more, should you be interested in exploring more. But the answer seems pretty clear to me…