Environmental Risk Factors for Multiple Sclerosis: A Case-control Study in Kerman, Iran

Mahlagha Dehghan, Fatemeh Ghaedi-Heidari


Background: Several studies have addressed the environmental risk factors for multiple sclerosis (MS). Concerning contradictory results and change of epidemiologic patterns and the role of environmental factors, in the present study, some risk factors, especially environmental factors, on MS were studied.

Materials and Methods: This was a retrospective case‑control study conducted among 120 patients with MS and 360 healthy individuals in Kerman, Iran. Inclusion criteria included (1) MS disease, diagnosed by a neurologist according to the McDonald criteria, and (2) tendency to participation in the study. Exclusion criteria included (1) suffering from cognitive disorders; (2) incomplete questionnaire; and (3) continuous migration. Data were collected using a questionnaire consisting of personal information and some environmental factors. Data were analyzed using descriptive and inferential statistics.

Results: The results showed that diet was associated with a higher risk of MS with the odds ratio (OR) of 14.46 and 95% confidence interval (CI) of 3.02–69.21 (p < 0.001) for vegetarian and OR of 11.74, 95% CI of 4.66–29.57 (p < 0.001) for animal diets. Similarly, vitamin D supplementation contributed to MS risk (OR: 2.27, 95% CI: 1.32–3.89; p < 0.001). In contrast, history of using cow’s milk during infancy resulted in a lower risk of MS (OR: 0.33, 95% CI: 0.20–0.52, p < 0.001).

Conclusions: This study suggests that different lifestyles including using cow’s milk during infancy and avoiding only vegetarian and animal diets may reduce MS risk in southeastern Iran. More studies are suggested to investigate the controversial finding of the negative effect of vitamin D supplementation in this area.


Case-control study, environmental exposure, multiple sclerosis

Full Text:



Hinkle JL, Cheever KH. Brunner & Suddarth’s textbook of medical‑surgical nursing. 14th ed. Vol. 1. Philadelphia: Lippincott Williams & Wilkins; 2017.

Kingwell E, Marriott JJ, Jetté N, Pringsheim T, Makhani N, Morrow SA, et al. Incidence and prevalence of multiple sclerosis in Europe: A systematic review. BMC Neurol 2013;13:1.

Mokry LE, Ross S, Ahmad OS, Forgetta V, Smith GD, Leong A, et al. Vitamin D and risk of multiple sclerosis: A Mendelian randomization study. PLoS Med 2015;12:e1001866.

Behrouz M, Hosseini Z, Sedaghat F, Soufi M, Rashidkhani B. The relationship between Food Groups and Multiple Sclerosis disease: A case‑control study in the Tehranian adult. J Sch Public Health Inst Public Health Res 2014;11:39‑53.

Etemadifar M, Izadi S, Nikseresht A, Sharifian M, Sahraian MA, Nasr Z. Estimated prevalence and incidence of multiple sclerosis in Iran. Eur Neurol 2014;72:370‑4.

Saman‑Nezhad B, Rezaee T, Bostani A, Najafi F, Aghaei A. Epidemiological Characteristics of Patients with Multiple Sclerosis in Kermanshah, Iran in 2012. J Mazandaran Univ Med Sci 2013;23:97‑101.

Ebrahimi HA, Sedighi B. Prevalence of multiple sclerosis and environmental factors in Kerman province, Iran. Neurol Asia 2013;18:385‑9.

Sundström P, Wåhlin A, Ambarki K, Birgander R, Eklund A, Malm J. Venous and cerebrospinal fluid flow in multiple sclerosis: A case‑control study. Ann Neurol 2010;68:255‑9.

Bagheri M, Fayazi S, Elahi N, Tabesh H, Madjdinasab N. Exposure to tobacco smoke, sunlight, pets and farm animals and multiple sclerosis: A case‑control study in Ahvaz (Iran). J Health Syst Res 2014;9:1311‑20 (Persian).

Belbasis L, Bellou V, Evangelou E, Ioannidis JP, Tzoulaki I. Environmental risk factors and multiple sclerosis: An umbrella review of systematic reviews and meta‑analyses. Lancet Neurol 2015;14:263‑73.

Solomon AJ, Whitham RH. Multiple sclerosis and vitamin D: A review and recommendations. Curr Neurol Neurosci Rep 2010;10:389‑96.

Ashtari F, Jamshidi F, Shoormasti RS, Pourpak Z, Akbari M. Cow’s milk allergy in multiple sclerosis patients. J Res Med Sci 2013;18(Suppl 1):S62‑S5.

Siejka D, Taylor B, Ponsonby AL, Dwyer T, van der Mei I. Association between exposure to farm animals and pets and risk of Multiple Sclerosis. Mult Scler Relat Disord 2016;10:53‑6.

Sellner J, Kraus J, Awad A, Milo R, Hemmer B, Stüve O. The increasing incidence and prevalence of female multiple sclerosis—a critical analysis of potential environmental factors. Autoimmun Rev 2011;10:495‑502.

Koch‑Henriksen N, Sørensen PS. The changing demographic pattern of multiple sclerosis epidemiology. Lancet Neurol 2010;9:520‑32.

Meysamie A, Ghaletaki R, Zhand N, Abbasi M. Cigarette Smoking in Iran. Iran J Public Health 2012;41:1.

Thompson AJ, Banwell BL, Barkhof F, Carroll WM, Coetzee T, Comi G, et al. Diagnosis of multiple sclerosis: 2017 revisions of the McDonald criteria. Lancet Neurol 2018;17:162‑73.

Asadollahi S, Fakhri M, Heidari K, Zandieh A, Vafaee R, Mansouri B. Cigarette smoking and the associated risk of multiple sclerosis in the Iranian population. J Clin Neurosci 2013;20:1747‑50.

Hedström AK, Hillert J, Olsson T, Alfredsson L. Smoking and multiple sclerosis susceptibilities. Eur J Epidemiol 2013;28:867‑74.

Manouchehrinia A, Tench CR, Maxted J, Bibani RH, Britton J, Constantinescu CS. Tobacco smoking and disability progression in multiple sclerosis: United Kingdom cohort study. Brain 2013;136:2298‑304.

McKay KA, Tremlett H. The systematic search for risk factors in multiple sclerosis. Lancet Neurol 2015;14:237‑8.

Khadilkar SV, Sahni AO, Agarwal S. A case‑control study of environmental risk factors in Indians with multiple sclerosis. Neurol Asia 2005;10:47‑52.

Hedström AK, Hillert J, Olsson T, Alfredsson L. Alcohol as a modifiable lifestyle factor affecting multiple sclerosis risk. JAMA Neurol 2014;71:300‑5.

Turner AP, Hawkins EJ, Haselkorn JK, Kivlahan DR. Alcohol misuse and multiple sclerosis. Arch Phys Med Rehabil 2009;90:842‑8.

Bäärnhielm M, et al. Sunlight is associated with decreased multiple sclerosis risk: no interaction with human leukocyte antigen‑DRB1 15.Eur J Neurol 2012;19(7):955‑62.

Bjørnevik K, Hedström AK, Kockum I, Sundqvist E, Gustafsson SA, Hillert J, et al. Sun exposure and multiple sclerosis risk in Norway and Italy: The EnvIMS study. Mult Scler 2014;20:1042‑9.

Alonso A, Cook SD, Maghzi AH, Divani AA. A case‑control study of risk factors for multiple sclerosis in Iran. Mult Scler 2011;17:550‑5.

Hewer S, Lucas R, van der Mei I, Taylor BV. Vitamin D and multiple sclerosis. J Clin Neurosci 2013;20:634‑41.

Manouchehrinia A. [Tobacco smoking and multiple sclerosis: Effects on the occurrence, progression, and mortality] [Thesis submitted to the University of Nottingham for the degree of Doctor of Philosophy] University of Nottingham; 2014.

Mowry EM, Krupp LB, Milazzo M, Chabas D, Strober JB, Belman AL, et al. Vitamin D status is associated with relapse rate in pediatric‑onset multiple sclerosis. Ann Neurol 2010;67:618‑24.

Ascherio A, Munger KL, White R, Köchert K, Simon KC, Polman CH, et al. Vitamin D as an early predictor of multiple sclerosis activity and progression. JAMA Neurol 2014;71:306‑14.

Martinelli V, Dalla Costa G, Colombo B, Dalla Libera D, Rubinacci A, Filippi M, et al. Vitamin D levels and risk of multiple sclerosis in patients with clinically isolated syndromes. Mult Scler 2014;20:147‑55.

Niino M, Sato S, Fukazawa T, Masaki K, Miyazaki Y, Matsuse D, et al. Decreased serum vitamin D levels in Japanese patients with multiple sclerosis. J Neuroimmunol 2015;279:40‑5.

Mokry LE, Ross S, Timpson NJ, Sawcer S, Davey Smith G, Richards JB. Obesity and multiple sclerosis: A mendelian randomization study. PLoS Med 2016;13:e1002053.

Harirchian M, Bitarafan S, Honarvar N. Dairy Products Consumption in Multiple Sclerosis Patients: Useful or Harmful. Int J Neurorehabilitation 2016;3:e126.


  • There are currently no refbacks.