comparison of serum vitamin d level in multiple sclerosis patients, their siblings, and healthy controls.

background: multiple sclerosis (ms) is an autoimmune,  neuro- inflammatory disease  of  central nervous system affecting physical, emotional, and cognitive aspects of patients. association of vitamin d deficiency and ms has been shown in previous studies. the aim of this study was to evaluate serum vitamin d level in ms cases and their sex-matched healthy siblings (who are genetically near similar) and non-relative sex-matched healthy controls. methods: a total of 135 subjects enrolled in this case- control study. group one (n = 45) consisted of patients with established ms. group two (n = 45) included sex- matched healthy siblings of the group one and group three participants (n = 45) were non-relative sex- matched  healthy  controls.  demographic  data  (age, sex), level of education, daily sun exposure duration, and month of birth gathered for all. serum sample of all participants was collected for 25-hydroxy vitamin d measurement. results: there was no significant difference between vitamin d level, sun exposure duration, education level, and season of birth in three evaluated groups. mean vitamin d level was 8.2 ± 10.1 (nmol/l) in women and 13.3 ± 7 (nmol/l) in men (p = 0.001). there was a significant positive correlation between daily sun exposure duration and vitamin d level in whole participants (r = 0.28, p < 0.001) as well as in ms patients (r = 0.32, p = 0.030). mean vitamin d level was significantly lower  in  participants  who  have  born  in spring and summer. conclusion:  vitamin  d  deficiency  is  high  among iranian population as well as ms patients.