R1.1: meta-regression?

[jessexknight]

A limitation of this review, which the authors acknowledge, is that it is essentially an ecological analysis. Although there is an association between models allowing for heterogeneity in risk behaviour and models predicting smaller ART impacts on HIV incidence, this finding doesn't necessarily prove that heterogeneity in risk behaviour determines the extent of the ART impact. There are many possible confounders and other variables that influence the extent of the modelled reductions in HIV incidence, as the authors note. Would it not make more sense to use a meta-regression approach to isolate the effect of the heterogeneity assumptions, controlling for the confounding factors? Although this wouldn't completely get around the causality conundrum, it would be better than the current approach, which is effectively relying on univariable rather than multivariable analysis.