Data collection and analysis—At least two review authors extracted data independently from
included papers. We contacted authors of trials for additional and missing data. We calculated risk
ratios (RR) and 95% confidence intervals (CI) of homogeneous dichotomous data. We used a
fixed-effects model for heterogeneous dichotomous data. Where possible we also calculated the
numbers needed to treat (NNT), as well as weighted means for continuous data.