How does smoking affect a patient with ankylosing spondylitis (AS)?

Mechanism of Smoking in Ankylosing Spondylitis

Direct Clinical Impact

Smoking independently worsens disease activity, accelerates structural damage, and impairs functional outcomes in patients with ankylosing spondylitis through mechanisms involving increased systemic inflammation and earlier disease onset. 1, 2

Pathophysiological Mechanisms

Inflammatory Amplification

• Smoking increases systemic inflammatory markers, with current smokers showing significantly elevated ESR compared to non-smokers (p = 0.03) 3
• MRI studies demonstrate that smoking is independently associated with more frequent sacroiliac joint inflammation (OR 1.57, p=0.02) and spinal inflammation (OR 2.33, p<0.001) 2
• The inflammatory burden translates to higher disease activity scores, with current smokers showing BASDAI scores 14.75 points higher than non-smokers (p < 0.001) 4

Structural Damage Acceleration

• Cumulative smoking exposure (pack-years) is independently associated with higher modified Stoke AS Spine Score (mSASSS), with each pack-year increasing the score by 0.26 points (p = 0.005) 4
• Smokers demonstrate more frequent MRI structural lesions in both sacroiliac joints (OR 1.54, p=0.03) and spine (OR 2.02, p=0.01) compared to non-smokers 2
• Smoking intensity correlates strongly with radiographic spinal damage (r = 0.683, p < 0.001) 4

Disease Onset and Progression

• Smoking is associated with earlier onset of inflammatory back pain, occurring 1.46 years earlier than in non-smokers (p=0.04) 2
• Current smoking at baseline is associated with incident AS development (OR 1.99,95% CI 1.28-3.11, p = 0.002), suggesting a role in disease initiation 5
• The duration of inflammatory back pain correlates positively with pack-years of smoking (r = 0.628, p < 0.001) 4

Functional and Quality of Life Impact

Physical Mobility Impairment

• Smokers show significantly worse spinal mobility across multiple parameters: modified Schober's index (p < 0.001), cervical rotation (p = 0.034), lateral lumbar flexion (p = 0.002), chest expansion (p = 0.016), and occiput-to-wall distance (p = 0.003) 3
• Smoking intensity correlates with functional disability (BASFI r = 0.481, p = 0.005) and specific mobility measures including fingertip-to-floor distance (r = 0.485, p = 0.004) 3
• Ever smokers have significantly higher BASFI scores compared to never smokers (p = 0.035) 4

Quality of Life Deterioration

• Smoking is independently associated with poorer health-related quality of life across multiple domains: EuroQol (B=1.38, p<0.001), SF-36 physical component (B=-4.89, p<0.001), and mental component scores (B=-5.90, p<0.001) 2

Clinical Implications for Management

Smoking Cessation Benefits

• Patients who quit smoking demonstrate significant improvements within 6 months across multiple disease parameters 6
• BASDAI decreases significantly after smoking cessation (p = 0.001), with quitters showing lower disease activity than continuing smokers at 6 months (p = 0.02) 6
• Functional status improves after cessation, with BASFI scores decreasing (p = 0.001) and chest expansion increasing (p = 0.001) 6
• Pulmonary function improves, with FEV1 (p = 0.003) and FVC (p = 0.007) showing significant gains after cessation 6
• Quality of life parameters improve, including AS-QoL (p = 0.003) and multiple SF-36 domains (physical function p = 0.015, pain p = 0.036, general health p = 0.05) 6

Guideline Recommendations

• The ASAS/EULAR guidelines explicitly recommend that patients should be educated about AS and strongly encouraged to stop smoking 1
• Smoking cessation is positioned alongside exercise and physical therapy as a core non-pharmacological intervention 1
• Cross-sectional studies consistently demonstrate poorer functional outcomes in AS patients who smoke, establishing smoking as a recognized prognostic indicator 1

Critical Clinical Pitfalls

• Do not underestimate the magnitude of smoking's impact—it affects disease activity as significantly as many pharmacological interventions, with effect sizes comparable to biologic therapy in some parameters 4, 2
• Recognize that smoking intensity (pack-years) matters more than smoking status alone for structural damage progression, requiring detailed smoking history documentation 4
• Understand that the benefits of smoking cessation are demonstrable within 6 months, providing a concrete timeline for patient counseling 6
• Current smoking status is more strongly associated with disease activity than past smoking, suggesting that cessation at any point may be beneficial 4