Lower average lifetime exposure to low levels of ultraviolet radiation (UVR) may increase the risk of multiple sclerosis (MS) in adults in the United States, according to results published in Multiple Sclerosis Journal.
The study included participants in the third and fourth surveys of the US Radiologic Technologists Cohort study (n=39,801). Participants completed residential histories and reported MS diagnoses. Neurologists who specialize in MS conducted medical record reviews, confirming 148 cases of MS among participants.
The researchers matched residential locations throughout participants’ lives to satellite data from NASA’s Total Ozone Mapping Spectrometer project in order to estimate UVR exposure.
The results indicated that participants’ MS risk increased as average lifetime levels of UVR exposure in winter decreased, and this effect remained consistent across age groups <40 years (HR 1.59 for <12 years old, HR 1.55 for 13-19 years old, and HR,1.57 for 20–39 years old).
The researchers did not find significant evidence that low UVR exposures during summer or at older ages were linked to the risk of developing MS. Compared with spending ≥5 hours a day outside, spending <1 hour/day outdoors in summer was linked to a nonsignificant increased risk for MS for ages 20 to 39 (HR 1.92; 95% CI, 0.59-6.20) and 40 to 64 (HR 1.71; 95% CI, 0.42-7.05).
“Future studies of UVR and MS should evaluate the reproducibility of the findings, incorporate multiple sources of vitamin D exposure, and consider susceptibility factors, such as genetic markers, to elucidate pathogenesis mechanisms and identify susceptible subgroups,” the researchers wrote.
Gallagher LS, Ilango S, Wundes A, et al. Lifetime exposure to ultraviolet radiation and the risk of multiple sclerosis in the US radiologic technologists cohort study [published online June 22, 2018]. Mult Scler. doi:10.1177/1352458518783343