Smoking as a risk factor for development of Secondary Progressive Multiple Sclerosis: A study in IRAN, Guilan

BackgroundCigarette smoking seems to contribute to susceptibility and progression of multiple sclerosis (MS).Although the incidence of MS in Iranian population has increased during recent years, the effects of smoking on progression of MS have not been studied. The aim of this study was to investigate the association between cigarette smoking and development of secondary progressive MS (SPMS) in Iranian patients with MS.MethodsThis study was carried out on patients registered in the MS Society (Guilan, Iran) database. Using a structured questionnaire, information on smoking status of 400 of patients could be obtained. The association between cigarettes smoking and SPMS was analyzed by Cox regression model.ResultsThe relationship between smoking and development of SPMS was still evident after adjusting for age at disease onset, gender and number of relapses per year (P = 0.004). Smoking more than 10 cigarettes per day increased risk of development of SPMS (HR: 2.43; 95% CI: 1.28 to 4.6; P = 0.007).ConclusionsOur results indicated that smokers have an increased risk for progression of relapsing-remitting MS (RRMS) to SPMS compared with non-smokers. We also showed that the disease progression may be influenced by increase of cigarette smoking.