Vitamin D genetic risk scores in multiple sclerosis

Background Low serum 25(OH)D-3 (vD) is an environmental risk factor for multiple sclerosis (MS). Lower vD levels during early disease may be associated with long-term disability. Determinants of serum vD levels in healthy individuals include supplementation behaviour and genetic factors. These determinants have been less well studied in people with MS (pwMS). Methods We developed a vD-weighted genetic risk score (GRS) and validated this in 373,357 UK Biobank participants without MS. We measured serum 25(OH)D-3 and genotyped six vD-associated SNPs (rs12785878, rs10741657, rs17216707, rs10745742, rs8018720, rs2282679) in a cohort of pwMS (n = 315) with age and geographically matched controls (n = 232). We then assessed predictors of serum vD concentration in this cohort. Results The GRS was strongly associated with vD status in the Biobank cohort (p < 2 x 10(-16)). vD supplementation, having MS, lower BMI, increased age and supplementation dose were associated with higher vD levels (false discovery rate, FDR < 5%). In multivariable models adjusting for supplementation, BMI, age, sex, and MS status, the GRS was strongly associated with vD level (p = 0.004), but not in those who supplemented (p = 0.47). Conclusions Our findings suggest that vD supplementation is the major determinant of vD level in pwMS, with genetic determinants playing a far smaller role.

Automated summary

This study demonstrates that vD supplementation is the major determinant of vD levels in people with MS, with genetic factors playing a smaller role.