Waterpipe and cigarette smoking and drug and alcohol consumption, and the risk of primary progressive multiple sclerosis: A population-based case-control study.

Background: Multiple sclerosis (MS) is a chronic central nervous system disease, and primary progressive multiple sclerosis (PPMS) is one the main types of MS, which has unknown environmental risk factors. The present study was conducted with the aim to identify the association of waterpipe and cigarette smoking, substance abuse, and alcohol consumption with the risk of PPMS development. Methods: A population-based, case-control study was conducted in Tehran, Iran, on 146 PPMS cases and 294 controls. PPMS cases were diagnosed and confirmed by neurologists. Standard random digit dialing was used to select sex-matched healthy control participants from the same source population as the cases. Logistic regression analysis was used to estimate unadjusted and adjusted odds ratios (OR). Results: In total, 440 subjects participated in the study. PPMS was associated with ever smoking cigarettes [OR = 2.48; confidence interval (CI) = 1.44-4.27], and passive smoking (OR = 2.20; CI = 1.34-3.62). However, having ever smoked waterpipe was not significantly associated with PPMS risk (OR = 1.19; CI = 0.62-2.26). Those who had all 3 types of smoking had an accumulative OR that was 10.45 times higher than that in individuals without any type of smoking (OR: 10.45; 95% CI = 3.5-31.2). We did not find any significant association between PPMS risk and substance abuse and alcohol consumption. Conclusion: Cigarette smoking and being exposed to passive smoking are important risk factors for developing PPMS; in addition, the use of 3 types of smoking, showed an OR higher than that in those without any smoking. Considering the global increase in tobacco smoking, this finding emphasizes the importance of interventional programs for the prevention of tobacco smoking.