Vitamin D, smoking, EBV, and long-term cognitive performance in MS: 11-year follow-up of BENEFIT.

Cortese M, Munger KL, Martínez-Lapiscina EH, Barro C, Edan G, Freedman MS, Hartung HP, Montalbán X, Foley FW, Penner IK, Hemmer B, Fox EJ, Schippling S, Wicklein EM, Kappos L, Kuhle J, Ascherio A; BENEFIT Study Group.