Study objective: We aim to clarify causal associations and mechanisms between vitamin D, hypertension and AF risk, using two large and homogenous populations from the Norwegian HUNT and the UK Biobank studies as well as publicly available GWAS

Specific research questions:

I) Is serum vitamin D status causally associated with the risk of hypertension?
II) What is the prospective association between serum vitamin D and AF and whether hypertension mediates the association?
III) Is vitamin D status a causal factor for the development of AF and whether hypertension genetically mediates the association-evidence from the Mendelian randomization methods?