Tobacco and Multiple Sclerosis
The negative impact of smoking on MS is well established, however, there is much less evidence on whether smoking cessation is beneficial for progression in MS.
Adults with MS registered in the UK MS Registry (2011-2020) formed this retrospective, prospective cohort study published in Brain.
Primary Outcomes were changes in 3 patient-reported outcomes (PROs): the standardized MS Physical Impact Scale (MSIS-29-Phys), the standardized MS Gait Scale (MSWS-12), and the Hospital Anxiety and Depression Scale (HADS-Anxiety and HADS-Depression).
A total of 7983 participants were included, of whom 4130 (51.7%) had ever smoked; of whom 1315 (16.5%) were current smokers and 2815/4130 (68.2%) were former smokers.
For all PROs, current smokers at the time of completing their first questionnaire had higher PRO scores indicating greater impairment compared with never smokers (∼10 point difference on MSIS-29-Phys and MSWS-12; 1.5-1.8 points for HADS-anxiety and HADS-depression).
There was no improvement in PRO scores with increasing time since smoking cessation in former smokers.
923 participants formed the prospective parallel group, which showed that MSIS-29-phy 5.03, MSWS-12 5.28, and HADS-depression 0.71, worsened over a 4-year period, while HADS-anxiety remained stable.
Current smokers had higher scores on the MSIS-29-Phys and HADS-Anxiety (3.05 [0.22, 5.88], 1.14 [0.52, 1.76]) while former smokers had a lower MSIS-29 score of -2.91 [-5.03, -0.79].
Continued smoking was associated with shorter time to event worsening in all PROs (MSIS-29-Phys: n = 4436, p = 0.0013; MSWS-12: n = 3902, p = 0.0061; HADS-anxiety: n = 4511, p = 0.0017; HADS-depression: n = 4511, p < 0.0001).
Worsening motor disability (MSIS-29-Phys and MSWS-12) was independent of baseline HADS-anxiety and HADS-depression scores. There was no statistically significant difference in the rate of worsening between never smokers and never smokers.
When smokers quit smoking, there was a slowing of the rate of motor impairment deterioration so that it matched the rate of motor impairment of never smokers. This suggests that smoking cessation is beneficial for people with MS.