Journal of Multiple Sclerosis

A Link between Smoking and Age at Onset in Multiple Sclerosis

Cláudia Lima, Rita Machado, Zoi Argyropoulou, Inês Correia, Carla Cecília Nunes, Maria Carmo Macário, Lívia Sousa and Sónia Batista*

Background: Smoking has been suggested to increase susceptibility to Multiple Sclerosis (MS) and also disease progression, associated with higher disability and higher risk of conversion to progressive disease phenotypes. However, the effect of smoking and smoking intensity on MS progression remains unclear.

Objectives: The aim of this study was to investigate the influence of smoking and smoking intensity on the susceptibility to and progression of MS.

Methods: Demographic and clinical data were collected. Patients were divided according to their smoking status at the time of MS onset (non-smokers and regular-smokers) or current smoking status (non-smokers, current-smokers, past-smokers and secondhand smokers). Statistical analysis was performed using SPSSv20.0, and a p-value<0.05 was considered statistically significant. Results: 120 patients (73.3% were female) with a mean age of 44.1 years were included. It was found that regular-smokers had an early onset of disease compared to non-smokers (29.5 vs. 34.2, respectively, p=0.031). Age of disease onset was directly correlated with pre-onset pack-year (r=0.295; p=0.002). A significant difference in the gender distribution was observed among the different smoking status groups (p<0.001). Most females were non-smokers (56.8%), while males were past-smokers (53.1%).

Conclusions: Our findings suggest that smoking is associated with an anticipation of the age at onset of MS, reinforcing the role of smoking as a risk factor to MS.