Table 2. Summary of studies included assessing the relation between serum vitamin D levels and disease activity.

RRMS - Relapsing-Remitting Multiple Sclerosis, CIS - Clinically Isolated Syndrome, CDMS - Clinically Definite Multiple Sclerosis

Simpson Jr et al., [40]; Fitzgerald et al., [41]; Kuhle J et al., [42]; Mc Laughlin et al., [43] 

REFERENCES	DESIGN	SAMPLE SIZE	POPULATION	OBJECTIVES	CONCLUSION
Simpson Jr et al., (2010)	Prospective cohort study	145	Residents of Southern Tasmania and Australia from 2002 to 2005 with RRMS	To observe relapse rates in patients of RRMS with higher levels of 25(OH)D	12% decrease in relapse risk  for each 10nmol/l increase in serum 25(OH)D was observed
Fitzgerald et al., (2015)	Prospective cohort study	1796	Patients with RRMS and on IFN- β  therapy from 26 countries	To assess the association between 25(OH)D and disease activity and progression	A 50.0-nmol/L increase in serum 25(OH)D levels was associated with a 31% lower rate of new lesions
Kuhle et al., (2015)	Multicenter study	1047	Patients with CIS from 17 different countries	Predictive value of 25(OH)D in CIS to CDMS conversion	Significant predictive value in univariate analysis. Diminished significance in multivariable analysis
Mc Laughlin et al., (2018)	Meta-Analysis	950	Participants of 12 clinical trials	To determine the therapeutic role of vitamin D in MS	Statistically insignificant differences in outcome measures