Table 1

Risk of bias

StudyStudy designDowns and Black Checklist61Oxford centre for evidence-based medicine level62
Rozzi et al66Case–control163b
McKeon et al77Randomised control trial171b
Sesma et al56Case series174
Beazell et al76Randomised control trial241b
Lee et al72Cohort study152b
Hoch et al43Case series184
Schaefer et al68Randomised control trial201b
Lubbe et al73Randomised control trial231b
Gilbreath et al59Case series194
Cruz-Diaz et al58Randomised control trial211b
Collins et al74Randomised control trial111b
De Ridder et al70Case–control183b
Salom-Moreno et al75Randomised clinical trial221b
Cruz-Diaz et al69Randomised clinical trial211b
McKeon et al57Randomised clinical trial231b
Donovan et al51Randomised clinical trial221b
Wright et al71Randomised clinical trial221b