Multiple sclerosis and ionizing radiation.

The etiology of multiple sclerosis (MS) may involve exposure to infectious, chemical or physical agents damaging the blood-brain barrier and an autoimmune reaction against myelin breakdown products. Here we report a pooled analysis of 174 MS cases and 815 population controls from two case-control studies with regard to such a potentially damaging exposure, namely X-ray examinations, radiological work and treatment with ionizing radiation. Exposure was assessed by questionnaires to the subjects. We obtained odds ratios of 4.4 (95% confidence interval, CI, 1.6-11.6) and 1.8 (95% CI 1.2-2.6) for radiological work and X-ray examinations, respectively; 5 cases, but no controls, in one of the studies had been treated with ionizing radiation. Our data and some other observations reported in the literature suggest a contributory role for ionizing radiation to the development of MS in some cases.