Aim and objective:
Recent studies have reported that smoking is associated with increased multiple sclerosis (MS) risk. Additionally, non-smokers have lower self-reported disability and smoking cessation resulted in the decreased risk of reaching disability milestones. Although some studies have reported that smoking is associated with anxiety and depression, little is known about other common symptoms in persons with MS (pwMS). Thus, the aim was to investigate the association between smoking and walking, fatigue, depression, and health-related quality of life in pwMS.

Methods:
This study included 279 (199 female) pwMS. The current smoking status and pack-years of smoking were evaluated. Walking was assessed using Timed 25-Foot Walk (T25FW), Six-Minute Walk Test (6MWT), and 12-Item MS Walking Scale (MSWS-12). Fatigue, depression and health-related quality of life were assessed using Modified Fatigue Impact Scale (MFIS), Beck Depression Inventory (BDI), and MS International Quality of Life questionnaire (MusiQoL), respectively. Disability level was assessed using Expanded Disability Status Scale (EDSS).

Results:
There were 95 (34.1%) current smokers (mean pack-years of smoking was 9.2 (SD 7.1) years). Current smokers had significantly worse MFIS (p=0.003, pη²=0.031), BDI (p=0.044, pη²=0.015), and MusiQoL (p=0.003, pη²=0.031) scores adjusting for age, gender, EDSS and disease duration compared to non-smokers. No significant difference was observed between smokers and non-smokers in walking and physical activity measures (p>0.05). Pack-years of smoking was significantly correlated with T25FW (r=0.574, p<0.001), 6MWT (r=-0.461, p<0.001), MSWS-12 (r=0.684, p<0.001), MFIS (r=0.370, p<0.001), MusiQoL (r=-0.259, p=0.012), and BDI (r=0.269, p<0.001) in smokers.

Conclusions:
Smokers have significantly more fatigue and depression levels and less health-related quality of life compared to non-smoker pwMS. Increased pack-years of smoking is associated worse walking ability, depression, fatigue and health-related quality of life levels. Smoking cessation may reduce walking impairment as well as fatigue and depression, additionally increase health-related quality of life in pwMS.