by Dr Valerie Milne
Smoking impacts Rheumatoid Arthritis (RA) at all stages of the disease and even its treatment. RA is a chronic autoimmune disease characterised by inflammation in the joints that, when left untreated, can cause irreversible cartilage loss and bone damage leading to deformity of the joints, loss of function, and long-term disability. More than 46% of people with RA have difficulty performing everyday activities (1). RA can affect other body parts like eyes, lungs, and blood vessels. Cardiovascular disease, also associated with smoking, is a well-known comorbidity (2,3).
The onset of RA can occur at any age, and half the people who develop RA are of working age. In New Zealand, more than 100,000 people over 15 live with RA, representing almost 25,000 disability-adjusted life years (DALYs), with men experiencing 8,708 DALYs and women 16,269 DALYs. These figures translate into high economic costs to the individual, the health system and society(4).
Smoking tobacco has impacts on RA at all stages of the disease process and its treatment:
- It is a known environmental trigger of RA.
- It impacts the patient’s response to disease-modifying medications (DMARDs) and disease progression.
- Smoking also increases the risk of some comorbidities, such as heart and lung diseases.
Smoking increases the risk of developing RA
Genetic and environmental factors combine to initiate RA, but these combinations are not yet fully understood. Not everyone with a genetic profile associated with RA will develop the disease, and while not all environmental factors are known, smoking tobacco has been consistently identified as a major contributor to the risk of developing RA that is associated with elevated levels of anti–cyclic citrullinated peptide (anti-CCP), which in turn is associated with more aggressive disease and severe joint erosion (5). Smoking may contribute up to 14% of RA and 35% of anti-CCP positive RA (6).
Smoking for longer increases the risk of RA
The length of time a person has smoked and how many cigarettes are both important RA risk factors (6) but the length of time a person has smoked may be more important. Twin studies indicate a doubling of the risk of RA after 20 years of smoking (7). Researchers estimate that at least ten years of non-smoking is needed for smokers to reverse the increased risk of RA (8,9). People who continue smoking after developing RA are likely to have worse symptoms, and joint damage is more likely than for people who stop smoking or have never smoked. Smoking also leads to more inflammation outside the joints, such as vasculitis (inflammation of the blood vessels) (10,11).
Smoking is likely to increase the severity of RA
The disease symptoms are worse for people who continue smoking after developing RA than those who stop smoking or have never smoked. The disease is active, and joint damage is more likely to occur.
Inflammation outside the joints, such as vasculitis (inflammation of the blood vessels), is also more likely to occur (10,11).
Smoking reduces the effectiveness of RA medications
Smoking also impacts how well disease-modifying medications (DMARDs) suppress disease. By measuring disease activity(1), researchers found that people with RA who continue to smoke have a worse response to both prednisone (12) (used to reduce pain and swelling) and methotrexate (mtx), which is the first-line DMARD used to suppress disease activity.
A study adhering to EULAR2 treatment response criteria shows that gender, duration, and age were significant predictors of poor response to mtx after 3 – 4 months of treatment. After adjusting for these criteria, current smoking was the only significant predictor of poor response to treatment (13).
Expensive biological disease-modifying drugs (bDMARDs) prescribed if the response to conventional DMARDs is insufficient to suppress disease activity significantly are also less effective if the recipient is a current smoker (14).
Smoking adds to the risk of RA comorbidities
RA does not only affect people’s joints. It may also affect major organs in the body. Heart and lung disease prevalence in people with RA is higher than for the general population, regardless of smoking status. Heart disease is the leading cause of early death (4 in 10) in people with RA (15). A 6-times risk of RA-Interstital Lung Disease (ILD) has been observed in people who have smoked for 30-pack years (16). People with RA are twice as likely as the general population to be hospitalised with chronic obstructive pulmonary disease (COPD)(17). Smoking also increases the risk of osteoporosis, the most common comorbidity in RA (1,18).
Passive smoking and RA
Evidence of a link between RA onset and passive smoking have been contradictory; however, a recent meta-analysis of six high-quality studies has found a 12% increase in RA prevalence in people exposed to passive smoking. Further studies are required to understand the pathway between passive smoking and RA (19).
Passive smoking in childhood
Smoke-free places are important during pregnancy and for children. While the risk of passive smoking in pregnancy is unclear, recent research has shown that passive smoking in childhood may significantly increase the risk of developing RA (20). The risk of developing RA is 34% higher for exposure to passive smoking in childhood (19).
E-cigarettes and vaping
The use of e-cigarettes (vaping) has grown rapidly as an alternative to cigarette smoking and a device to help people quit smoking. This growth is ahead of research into the impacts of vaping on RA and other inflammatory arthritis.
Potential risks of vaping, ahead of the research into possible hazards, need to be considered alongside the benefits of e-cigarettes to aid smoking cessation that could delay or possibly prevent the onset of anti-CCP positive RA (6,21).
Vaping may lead to the development of interstitial lung disease, for which RA is already a known risk (ILDs occur in approximately 5 – 10% of people living with RA, and about half of the people with RA have changes in lungs that could indicate an undetectable ILD(23).
Vaping has the potential to lead to the onset of RA or worsening of existing RA. In a cross-sectional study in the US, E-cigarette usage was associated with a 30-55% increased risk of inflammatory arthritis compared with people who had never vaped (24).
Smoking and Rheumatoid Arthritis Summary
Smoking is a key factor that people at risk of RA can control. Smoking is associated with the onset of RA. It increases the severity of the disease, increases the risk of less effective treatment outcomes, and adds to the likelihood of severe comorbidities like osteoporosis, cardiovascular and respiratory diseases.
Increasing awareness of the links between smoking and RA, including passive smoking (especially in childhood), is a first step that could reduce smoking among people at risk of RA.
Any effort to increase awareness and reduce smoking in this at-risk group increases the likelihood of better health outcomes and reduces the financial burdens of the disease for individuals, the health service and society.
Quitting smoking can reduce the risk of RA onset, the severity of the disease, and its comorbidities. People with RA should also avoid passive smoking to reduce their risk of developing related diseases. Quit smoking resources are available from your GP, or call Quitline free on 0800 778 778 or text 4006 or visit the Smokefree website. Vaping might not be a safe alternative to tobacco smoking or a good choice for quitting smoking for people at risk of or those who have RA or other inflammatory arthritis (22).