Genetics

This post covers Rhead and colleagues' 2016 study in Neurology: Genetics, a Mendelian randomization analysis using individual-level data from 7,391 MS cases and 14,777 controls across California and Sweden, with a three-SNP instrument for serum 25-hydroxyvitamin D. It reports the pooled odds ratio of 0.85, converts the per-unit effect onto a per-standard-deviation scale derived from the paper's own allele frequencies and weights, covers the adjustment for HLA type and a 110-variant polygenic score, the empirical tests of the MR assumptions including the one disclosed violation, what the per-SNP analysis reveals about the largest-weighted SNP, the null results for severity and age at onset, and the sample overlap with the earlier summary-level MR.