title: X-ray radiation and the risk of multiple sclerosis: Do the site and dose of exposure matter?
abstract: BACKGROUND
  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.
  
  
  METHODS
  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 Xray radiation consisted of job-related X-ray exposure, radiotherapy, radiographic evaluations including chest Xray, 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.
  
  
  RESULTS
  History of both diagnostic [OR=3.06 (95% CI: 1.32-7.06)] and therapeutic [OR=7.54 (95% CI: 1.5935.76) 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].
  
  
  CONCLUSIONS
  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.
authors.affiliation: 1. MD, Associate Professor, Department of Neurology, Firoozgar Hospital, Iran University of Medical Sciences; Tehran, Iran. mrmotamed2005@yahoo.com.
authors.forename: Mohammad Reza
authors.initials: MR
authors.lastname: Motamed
authors.affiliation: 2. MD, M.P.H PhD, student and researcher, Division of Clinical geriatrics, Department of Neurobiology, Care Sciences, and Society (NVS), Karolinska Institutet, Stockholm, Sweden & Firoozgar Clinical Research Development Center (FCRDC), Firoozgar Hospital,Iran University of Medical Sciences; Tehran, Iran. sm_fereshtehnejad@yahoo.com.
authors.forename: Seyed-Mohammad
authors.initials: SM
authors.lastname: Fereshtehnejad
authors.affiliation: 3. MD, General practitioner and researcher, Medical Students Research Committee, Shahed University of Medical Sciences; Tehran, Iran. maryamabbasi1986@gmail.com.
authors.forename: Maryam
authors.initials: M
authors.lastname: Abbasi
authors.affiliation: 4. MD, AssistantProfessor, Department of radiology, Iran University of Medical Sciences; Tehran, Iran. mastanehsanei@yahoo.com.
authors.forename: Mastaneh
authors.initials: M
authors.lastname: Sanei
authors.affiliation: 5. MD, General practitioner and researcher, Department of Neurology, Firoozgar Hospital, Iran University of Medical Sciences; Tehran, Iran. m.abbaslou@yahoo.com.
authors.forename: Mina
authors.initials: M
authors.lastname: Abbaslou
authors.affiliation: 6. MD, General practitioner and researcher, Department of Neurology, Firoozgar Hospital, Iran University of Medical Sciences; Tehran, Iran. somayehmeysami203@yahoo.com.
authors.forename: Somayeh
authors.initials: S
authors.lastname: Meysami
keywords: Association; Multiple Sclerosis; Radiation; Risk factor; X-ray