Relation Between Smoking and Disability Progression in Iranian Multiple Sclerosis Patients: A Case-Control Study.

Background: To compare characteristics of patients with multiple sclerosis (MS) between cigarette smokers and non-smokers.

Methods: A case-control study was performed on patients registered in the Kashani MS center from April 2019 to April 2020 in Isfahan, Iran. In total, 136 smoker patients and 220 non-smokers participated in the study and completed the questionnaire.

Results: The frequency of male gender in the smoker group was significantly higher than in the non-smokers (64.7% vs. 15%, P < 0.001). The mean age at MS onset was 31.5 ± 9.60 years among cigarette smokers and 29.7 ± 9.47 years among non-smokers (P = 0.794). Furthermore, 80% of cigarette smokers and 64% of non-smokers had at least one relapse per year (ARR ≥1, P < 0.001). The Expanded Disability Status Scale (EDSS) of more than 4.5 was significantly higher in smokers (26.5% vs. 18%, P = 0.023). There was a relation between an EDSS of more than 4.5 and an interval between smoking initiation and disease onset (P = 0.004). Long duration of smoking was associated with a higher disability scale (16.4 ± 9.5 vs. 9.8 ± 7.3, P = 0.008). Men smoked for a longer period of time before developing MS than women (9.24 ± 10.07 vs. 4.47 ± 7.61, P = 0.002). The average daily cigarette consumption was 7.74 ± 6.65 in women and 10.84 ± 9.44 in men (P = 0.024). Duration of smoking before the onset of the disease was 4.47 ± 7.61 years in women and 9.24 ± 10.07 in men (P = 0.002).

Conclusions: Our data suggest that there is a possible relationship between disability score and the duration of smoking before the onset of MS. It also revealed that the duration of smoking can affect the progression of the disease. Further studies are suggested to confirm these findings.