Both active and Passive Smoking Negatively Impact Multiple Sclerosis activity and progression

Recent findings published in Journal of Neurology Neurosurgery and Psychiatry, by researchers in Sweden indicate that both smoking and passive smoking have a negative influence on MS and that smoking cessation post diagnosis may be an important secondary preventive measure.

Continued smoking after MS diagnosis has consistently been associated with faster disease progression, whereas other studies have observed deceleration of the disease progression following smoking cessation. Since smoking is a modifiable risk factor in MS, cessation of smoking is important. However, several MS-specific barriers to smoking cessation have been identified in qualitative studies, and patients have expressed insecurity about whether nicotine replacement therapy would be safe in MS or in combination with MS disease-modifying treatment.

Moist snuff is a traditional Scandinavian smokeless tobacco product to place behind the upper lip. Snuff use delivers high amounts of nicotine without airway irritation and has not been associated with the risk of developing MS, but the possible impact of nicotine on MS disease progression has not previously been investigated. This is also the case for passive smoking, which is associated with increased MS risk, but has not been evaluated against progression.

Wu J et al followed up 9089 patients with MS from two case–control studies through the Swedish MS registry to investigate the impact of smoking (including smoking cessation), exposure to passive smoking and snuff use, using clinical and self-reported outcome measures.

They found that apart from active smoking, exposure to passive smoking appears to negatively influence disease activity and progression in MS. They also replicated previous findings of smoking as a risk factor in MS, and therefore that smoking cessation after diagnosis is an important secondary preventive measure. Snuff use was not associated with higher disease activity or progression, suggesting that nicotine replacement therapy could be a safe way to increase the chance of quitting smoking among patients with MS.

Smokers at baseline who stopped smoking post diagnosis did not significantly differ regarding disease outcomes compared with non-smokers at baseline, suggesting that the detrimental influence of smoking abates after smoking cessation. A reduction of systemic inflammation and oxidative stress following smoking cessation may contribute to the favourable effect on disease outcomes.

An inverse dose–response correlation has been shown between cumulative dose of snuff use and subsequent MS risk and snuff use also appears to have beneficial effects on the progression of the disease. Tobacco contains numerous substances, and our study cannot formally rule out any of them as responsible for the current observation; however, nicotine is the most likely compound, in view of its active anti-inflammatory role. Nicotine exerts anti-inflammatory and immune-modulating effects through a mechanism dependent on the alpha7 nicotinic receptor and has been shown to suppress neuroinflammation and disease severity in experimental autoimmune encephalomyelitis.

Considering the negative impact of smoking on disease progression, smoking cessation is crucial. However, more than 80% of those who were smokers at MS diagnosis remained smokers 5 years post diagnosis. “Efforts should thus be made to better understand patient-specific barriers to stopping smoking and provide smoking cessation support for patients with MS. Nicotine replacement therapy could be part of such cessation support”, say the authors.

The research concludes that both current smoking and current exposure to passive smoking negatively impacts disease progression in patients with MS. Their finding that snuff use is not associated with worse disease progression indicates that nicotine replacement therapy could be an attractive way to increase the chance of quitting smoking post diagnosis.

Reference

Wu J, Olsson T, Hillert J, Alfredsson L, Hedström AK. Influence of oral tobacco versus smoking on multiple sclerosis disease activity and progression. J Neurol Neurosurg Psychiatry. 2023 Aug;94(8):589-596. doi: 10.1136/jnnp-2022-330848