When Mendelian randomisation fails
Dr Martin Kohlmeier, Emmanuel Baah
BMJ Nutrition, Prevention & Health, doi:10.1136/bmjnph-2021-000265
Mendelian randomisation (MR) is the ingenious approach of using the consistent long-term modulation of interesting exposure variables by inborn genetic differences to mimic the effect of different levels on outcomes of interest. This type of analysis is particularly important for evaluating the causal impact of nutritional exposures on longterm health outcomes. The MR approach is predicated on equivalent effects of exposure and genetic proxy on the outcome. But what happens when the proxy is not a good predictor of the outcome of interest? MR analysis of the hypothesised role of vitamin D in the pathology related to SARS-CoV-2 infection illustrates this conundrum. Up to this point, a growing number of observational studies appeared to link low 25-hydroxy vitamin D (25-OHD) concentrations to higher risk
Competing interests None declared. Patient consent for publication Not required.
References
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