Sun exposure, vitamin D intake and progression to disability among veterans with progressive multiple sclerosis.

ABSTRACT

BACKGROUND: Early life events have been suggested to influence multiple sclerosis (MS) susceptibility, and to potentially modulate its clinical course. We assessed vitamin D-related exposures from childhood to disease onset and their associations with MS progression. METHODS: Among veterans in the Multiple Sclerosis Surveillance Registry, 219 reported having the progressive form and met the inclusion criteria. Participants reported their past sun exposure, vitamin D-related intake and age at disability milestones using the Patient-Determined Disease Steps (PDDS). The Cox proportional hazards model was used to examine the association between vitamin D-related exposures and time (years) to disability. RESULTS: Low average sun exposure in the fall/winter before disease onset was associated with an increased risk of progressing to a PDDS score of 8 (hazard ratio, HR 2.13, 95% confidence interval, CI 1.20-3.78), whereas use of cod liver oil during childhood and adolescence was associated with a reduced risk (HR 0.44, 95% CI 0.20-0.96). CONCLUSIONS: These results suggest that exposure to vitamin D before MS onset might slow disease-related neurodegeneration and thus delay progression to disability among patients with the progressive subtype.