Sun exposure, vitamin D and age at disease onset in relapsing multiple sclerosis

Current evidence suggests that sun exposure and vitamin D intake, during childhood and adolescence, are associated with a reduced risk of multiple sclerosis (MS). However, the role of these environmental agents in the timing of disease symptom onset remains to be investigated.

Using a cross-sectional study design, we recruited participants from the Veterans Health Administration-Multiple Sclerosis Surveillance Registry. Self-reported histories of residential locations, sun exposure and intake of vitamin D were used to estimate vitamin-D-related exposures. Multivariable linear regression analysis was used to examine the associations between these variables and age at MS onset.

Among veterans with relapsing MS who resided in low-to-medium solar radiation areas (n = 540), low sun exposure in the fall/winter during the ages of 6-15 years was significantly associated with earlier symptom onset by 2.1 years (p = 0.02). Intake of cod liver oil during the same age period was associated with later onset of MS symptoms by 4 years (p = 0.02).

The current study provides evidence for an association between vitamin-D-related exposures during childhood and early adolescence and the timing of MS symptom onset, and supports vitamin D as a potential modulator of the clinical course of this disease.