Residential Radon Exposure and Multiple Sclerosis: a Pilot Study

Environmental risk factors for Multiple Sclerosis (MS) are not clearly understood, although vitamin D and sunlight exposure are thought to be protective. MS prevalence increases with increasing latitude, in a pattern similar to that of residential radon exposure, particularly in the U.S. To further study this relationship, a pilot study was conducted of ninety-seven MS patients and 51 non-MS patient controls. Patients had been diagnosed less than five years. An interview of the 148 patients included time spent on various living levels within the home as well as demographic, medical, residential, occupational, smoking, and other information. In a subset of the group who had lived in their homes for at least five years prior to diagnosis-25 MS and 21 control patients-radon detectors were placed for six months on different living levels in their homes. Time weighted average levels of radon exposure were calculated. Statistical methods included the t-test, odds-ratios, and logistic regression. Weekly cumulative radon values averaged 13,802.48 Bq m-3 h for cases and 9,369.14 Bq m-3 h for controls. The adjusted odds-ratio for MS prevalence increased by 1.98 (95%CI = 0.98 to 3.98, p = 0.06) for each unit increase in the time-weighted average of the natural log of radon exposure. Although not statistically significant, a trend of an increase in the probability of MS prevalence with each unit increase in the time-weighted average of the natural log of radon exposure was found. No statistically significant protective effect was found for either reported sunlight exposure or vitamin D use. Discussion of the strengths and weaknesses of the study is provided, as are recommendations for future research. A small sample size is a limiting factor in our conclusions.