I am responding to reviewer comments on a systematic review summarizing a number of risk factors. The exposure is any risk factor (this is what I am trying to make an overview of) and the outcome is first event of physical child abuse. The risk factors have been reported using various effect measures: relative risks (RR), odds ratios (OR), incidence rate ratios (IRR), and hazard ratios (HR). The study type varies, including prospective studies and cross-sectional designs.
I have a reviewer commenting that it is difficult to compare across these different effect measures, to which I agree - but am I correct to say that there is no single effect measure to which the others can be translated, that accurately would reflect the original estimate without using unreasonable assumptions?
For almost all papers the ratio estimates are adjusted for a number of covariates, so I can't just calculate them without access to the raw data. For some of these (maybe all?), the values would approach each other if the event studied is sufficiently rare - but I cannot guarantee it will be so in all studied populations.
I have tried to find an answer in Cochrane's handbook for systematic reviews, and looked around for primary articles with good solutions, but to no avail. This review (sorry, it is not open access): https://doi.org/10.1016/j.avb.2006.03.006 seems to join various effect measures in r-, d- and g-values, but using a program that has since been abandoned, and since I haven't seen this mentioned in Cochrane, I get the feeling that this may not be the desired approach anymore. It seems the calculations mentioned there is for standardized mean differences, and this would also only be appropriate for a continuous outcome - mine is dichotomous. I have also been through a number of systematic reviews on risk factors from various fields, either finding that these articles just postulates that everything is in odds ratios, report various measures as I do or simplify things, for example only reporting whether something is a risk or not, but no measure of magnitude.
Any advice would be highly appreciated.