en Neurology Neurology Original Research Original Research <p> <strong> Background: </strong>The sporadic cases of radiation-activated multiple sclerosis (MS) has been previously described, with a few studies focused on the relationship between radiation and the risk of MS. The aim of our study was to evaluate the association between history of X-ray radiation and MS. </p><p> <strong> Methods </strong>: This case-control study was conducted on 150 individuals including 65 MS patients and 85 age- and sex-matched healthy controls enrolled using non-probability convenient sampling. Any history of previous X-ray radiation consisted of job-related X-ray exposure, radiotherapy, radiographic evaluations including chest X-ray, lumbosacral X-ray, skull X-ray, paranasal sinuses (PNS) X-ray, gastrointestinal (GI) series, foot X-ray and brain CT scanning were recorded and compared between two groups. Statistical analysis was performed using independent t test, Chi square and receiver operating characteristics (ROC) curve methods through SPSS software. </p><p> <strong> Results </strong>: History of both diagnostic [OR=3.06 (95% CI: 1.32-7.06)] and therapeutic [OR=7.54 (95% CI: 1.59-35.76) X-ray radiations were significantly higher among MS group. Mean number of skull X-rays [0.4 (SD=0.6) vs. 0.1 (SD=0.3), p=0.004] and brain CT scanning [0.9 (SD=0.8) vs. 0.5 (SD=0.7), p=0.005] was higher in MS group as well as mean of the cumulative X-ray radiation dosage [1.84 (SD=1.70) mSv vs. 1.11 (SD=1.54) mSv p=0.008]. </p><p> <strong> Conclusion </strong>: Our study was one of the first to show higher history of X-ray radiation in patients with MS compared to healthy controls. A possible association was also found between the dose and the site exposed to X-ray radiation and risk of developing MS. </p> Multiple Sclerosis, Radiation, X-ray, Association, Risk factor. 975 982 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-1-758&slc_lang=en&sid=1 Mohammad Reza Motamed mrmotamed2005@yahoo.com 200319475328460014171 200319475328460014171 No Department of Neurology, Firoozgar Hospital, Iran University of Medical Sciences; Tehran, Iran. Seyed-Mohammad Fereshtehnejad sm_fereshtehnejad@yahoo.com 200319475328460014172 200319475328460014172 Yes Division of Clinical geriatrics, Department of Neurobiology, Care Sciences, and Society (NVS), KarolinskaInstitutet, Stockholm, Sweden &Firoozgar Clinical Research Development Center (FCRDC), Firoozgar Hospital, Iran University of Medical Sciences; Tehran, Iran. Maryam Abbasi maryamabbasi1986@gmail.com 200319475328460014173 200319475328460014173 No Medical Students Research Committee, Shahed University of Medical Sciences; Tehran, Iran. Mastaneh Sanei mastanehsanei@yahoo.com 200319475328460014174 200319475328460014174 No Department of radiology, Iran University of Medical Sciences; Tehran, Iran. Mina Abbaslou m.abbaslou@yahoo.com 200319475328460014175 200319475328460014175 No Department of Neurology, Firoozgar Hospital, Iran University of Medical Sciences; Tehran, Iran. Somayeh Meysami somayehmeysami203@yahoo.com 200319475328460014176 200319475328460014176 No Department of Neurology, Firoozgar Hospital, Iran University of Medical Sciences; Tehran, Iran