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  1. Does smoking cause MS?
  2. How could smoking cause MS?
  3. How does smoking affect people with MS?
  4. How does smoking affect disease progression in MS?
  5. What if I stop smoking now?
  6. What if I switch to vaping or low-nicotine tobaccos?
  7. Does my DMD protect me from the risks of smoking?
Cigarette burning in an ashtray

Nobody today would argue that smoking is good for you. However, there are several ways in which smoking is particularly unfavourable for people with MS.

Here is the current evidence on the risks of smoking for families affected by MS.

Does smoking cause MS?

MS is likely caused by a combination of genetic susceptibility combined with one or more environmental risk factors, such as infection with a virus or lack of vitamin D. Smoking is one of these risk factors for acquiring MS, and the general association between MS and smoking has been recognised for some years. Recent studies have looked in detail at the relationship between smoking and particular aspects of MS. Some of their findings include:

- You are more likely to get MS if you smoke

- You are more likely to get MS if your parents smoked when you were a child

- You are more likely to proceed from CIS to clinically defined MS if you smoke

- You are more likely to proceed from RRMS to SPMS if you smoke

- You are likely to experience more frequent relapses with RRMS if you smoke

- You are likely to experience more rapid disability progression with MS if you smoke

- You are likely to experience faster brain atrophy if you smoke

- You are more likely to acquire other autoimmune conditions or health problems if you smoke

A recent review looked at all the studies published between 1965 and 2018 and confirmed many of these findings. The authors recommend seeking help to quit smoking at a time and in a way that suits you.

If you have a genetic susceptibility for MS, then smoking makes the risk worse. As an example, 20% of all MS cases in Sweden are associated with smoking or passive smoking. However, among the people with MS who have the susceptible genetic type, 41% are associated with smoking or passive smoking.

So if you have MS, or a family member with MS, or if you know that you have a genetic susceptibility for MS, you should be aware that smoking or passive smoking is particularly risky for you and your children.

How could smoking cause MS?

The exact mechanisms are not clear, but one possibility is that exposure to cigarette smoke damages the endothelial cells that line the lungs. This causes chemical changes (methylation) to the DNA in those cells. As a result, the damaged cells produce a different balance of proteins to undamaged cells. It is possible that this imbalance makes the Blood-Brain Barrier weaker. Immune cells attracted to the damaged endothelial cells pass into the central nervous system and begin to attack the nerves. The more you smoke, the worse the effect.

With this theory, it is not the nicotine in cigarettes which is the problem, it is the irritation of the lungs. Similar effects are seen in exposure to other lung irritants like the substance produced by smoke machines used in entertainment, and also in general air pollution.

An alternative mechanism could be that smoking also causes hypoxia, which is a reduction in oxygen getting to the brain or other tissues. As a result, oxidative stress damages the glial cells in the Central Nervous System, which weakens the BBB.

How does smoking affect people with MS?

Smoking affects the disease course for people with MS in several ways, none of them positive. A recent study of people with MS made it clear that smokers reported a lower quality of life, more MS activity and greater disability.

Co-Morbidity

Co-morbidity means having more than one disease. If you smoke, you are more at risk of acquiring other autoimmune diseases, vascular diseases, type 1 diabetes or having a stroke, just like anyone else in the population. Having MS as well as another serious illness makes managing both diseases harder. In any given year, smokers with MS are twice as likely to die as non-smokers with MS. Much of this extra risk comes from co-morbidity, and the way in which symptoms of one disease make the other disease worse.

Pain

Smoking makes pain worse in MS. This includes neuropathic pain, back pain, headaches and painful spasms, Pain is a significant symptom for many people with MS, and can increase the likelihood of experiencing depression and fatigue. People with MS who smoke are more likely to report extreme pain than those who don't.

Pain, depression and smoking can make a vicious circle. It's hard to stop smoking if you think it is helping to manage your pain. If this is a problem for you, do seek extra support with pain management from your doctor or your MS team.

Bone fractures

Both smoking and MS are associated with reduced bone mineral density. The combination of both could put you at increased risk of fractures. 

Cognition

Smoking affects the brain, and is associated with cognitive decline, reduced brain volume and dementia in the general population. Our brains may naturally shrink as we age, and smoking accelerates this process. This reduces the cognitive reserve, or buffer zone, which allows our brains to remain flexible and deal with damage such as that caused by MS.

When people with CIS were scanned, smokers were found to have more lesions in their brain white matter and more abnormalities than non-smokers. Another study found that smokers with MS had reduced gray matter in the brain than non-smokers. Gray matter in the brain is made up of the nerve cell bodies, whereas white matter consists mostly of the axons and their support cells. A further study showed that heavy smokers with MS have increased cognitive impariment compared to non-smokers with MS.

How does smoking affect disease progression in MS?

At the first diagnosis of CIS, it has been shown that 67% of smokers go on to develop full clinically defined MS, compared to 35% of non-smokers. The best advice is to quit smoking at the time of diagnosis.

Recent studies have shown that smoking increases the relapse rate in people with RRMS, and also increases the risk of disease progression. Smokers are both more likely to get to advanced EDSS milestones, and more likely to get there sooner than non-smokers.

Smoking also increases the speed and risk of progression to SPMS. Smokers with RRMS got to the secondary progressive stage of MS approximately 4 years earlier than non-smokers. Every additional year of smoking after a diagnosis of RRMS accelerates the time to SPMS by 4.7%.

However, smoking has not been shown to affect the age of onset in PPMS, nor to influence disability progression in PPMS. There may be different underlying disease mechanisms as compared to RRMS.

What if I stop smoking now?

There is some good news - it is never too late to quit smoking. Stopping smoking can reduce many of the risks listed above. Every smoke-free year decreases your risk of progression to a greater level of disability, and ex-smokers have the same risk of progression in MS as non-smokers.

After you stop smoking, the changes to your cell DNA (methylation) steadily reduces. After 5 years, your lung epithelial cell DNA looks the same as that of a person who never smoked. Cutting down on the amount you smoke also helps reduce methylation.

What if I switch to vaping or low-nicotine tobaccos?

In recent years, personal devices to deliver a nicotine vapour have become widespread. However, the vaping industry is not standardised. The chemical composition of the products, the doses and the vaping technology itself is highly variable. Vaping is often described as being 'healthier' than cigarette smoking, but for people with MS this claim is not supported.

What little research has been done suggests that vaping could be just as bad for the Blood-Brain Barrier (BBB) as smoking, and is therefore bad for MS risk as well. Although the substances in vape liquids may be food grade, they have rarely been tested for inhalation. These substances may be just as irritating to the lung lining cells, and the process of vaping still causes localised hypoxia and oxidative stress.

This goes for low nicotine or nicotine free tobaccos, or smoked cannabis as well. It appears that the nicotine itself is not the problem for the BBB and MS, but the delivery mechanism is. For example, chewing tobacco has not been shown to increase MS risk. It is likely that nicotine patches or lozenges would be a more appropriate support mechanism than vaping if you are trying to quit smoking. 

Does my DMD protect me from the risks of smoking?

Disease modifying drugs have not been shown to reduce the risks of smoking for people with MS. A study of 834 Danish people with RRMS on beta interferon treatment found 27% more relapses among smokers than non-smokers, irrespective of their underlying genetic susceptibility. This implies that smoking makes your DMD less effective at protecting you from relapses.

Find out more

References

  • Manouchehrinia A, et al. Tobacco smoking and disability progression in multiple sclerosis: United Kingdom cohort study. Brain 2013;136(7):2298-2304 Full article
  • Marrie RA, et al. Smokers with multiple sclerosis are more likely to report comorbid autoimmune disease. Neuroepidemiology 2011;36(2):85-90. Full article
  • van der Vuurst de Vries RM et al Smoking at time of CIS increases the risk of clinically definite multiple sclerosis Journal of Neurology 2018 Feb 20 Full article
  • Petersen ER et al Smoking affects the interferon beta treatment response in multiple sclerosis Neurology Summary
  • Degelman ML and Herman KM Smoking and multiple sclerosis: A systemic review and meta-analysis using the Bradford Hill criteria for causation Multiple Sclerosis and Related Disorders 2017 17:207-216 Summary
  • Hedstrom AK et al The interaction between smoking and HLA genes in multiple sclerosis: replication and refinement European Journal of Epidemiology 2017 32 (10) 909-919 Full article
  • Paz-Ballesteros WC et al Cigarette smoking, alcohol consumptoin and overweight in multiple sclerosis: Disability progression Archives of Medical Research 2017 48(1) 113-120 Summary
  • Abul Kaisar, M et al A decade of e-cigarettes: limited research and unresolved safety concerns Toxicology 2016 July 15 67-75 Full article
  • Kaur, G et al Immunological and toxicological risk assessment of e-cigarettes European Respiratory Review 2018 28:27 (147) Full article
  • Jick SS et al Epidemiology of multiple sclerosis: results from a large observational study in the UK Journal of Neurology 2015 262(9) 2033-41 Full article
  • Ramanujam R et al Effect of smoking cessation on multiple sclerosis prognosis JAMA Neurology 2015 Oct 72 (10) 1117-23 Summary
  • Briggs FB et al Smokers with MS have greater decrements in quality of life and disability than non-smokers Multiple Sclerosis Journal 2017 (23 (13) 1772-1781 Summary
  • Rosso M and Chitnis T Association Between Cigarette Smoking and Multiple Sclerosis JAMA Neurol. Published online December 16, 2019. doi:https://doi.org/10.1001/jamaneurol.2019.4271 Summary
What causes MS?

What causes MS?

MS has no single cause, but there are several risk factors that make MS more likely to occur.

Risk of developing MS

Risk of developing MS

In the general population in the UK, about 1 in 650 people has multiple sclerosis (MS) with genes and environmental factors both playing a role. Read more about the risk of developing MS in this A-Z entry.

Pain

Pain

The two main types of pain in multiple sclerosis are nerve (neuropathic) pain and musculoskeletal (nociceptive) pain. Find out more about pain in this A-Z entry.

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