We investigated the association between smoking and the disease activity, functional ability, physical mobility, and systemic inflammation in Chinese ankylosing spondylitis (AS) patients. Seventy five male Chinese AS patients in Taiwan were enrolled in the cross-sectional study. These patients fulfilled the 1984 modified New York criteria. Patients completed the questionnaires, containing the demographic data, disease activity, functional ability (BASFI), and patient's global assessment. Meanwhile, physical examinations were performed to determine the patient's physical mobility. Acute-phase reactants, erythrocyte sedimentation rate (ESR), and C-reactive protein levels were also measured in the AS patients. Smoking habits with smoking duration and smoking intensity (pack-years of smoking) were recorded. Among these physical mobility parameters, modified Schober's index (p <0.001), cervical rotation (p = 0.034), later lumbar flexion (p = 0.002), chest expansion (p = 0.016), and occiput-to-wall distances (p = 0.003) were significantly impaired in smoking AS patients (n = 35) as compared to non-smoking (n = 40). Systemic inflammation parameter, ESR was significantly higher in smoking AS patients than non-smoking (p = 0.03). The odds ratio of advanced modified Schober's index, lateral lumbar flexion, fingertip-to-floor distance, chest expansion, and occiput-to-wall were significantly elevated in smoking AS patients as compared to non-smoking. Moreover, the smoking intensity correlated significantly with BASFI (r = 0.481, p = 0.005), cervical rotation (r = -0.401, p = 0.031), fingertip-to-floor distance (r = 0.485, p = 0.004), and occiput-to-wall distance (r = 0.473, p = 0.005) in the 35 smoking AS patients. The cigarette smokers in the Chinese AS patients have increased systemic inflammation and poor physical mobility. In addition, the higher smoking intensity in the AS smokers is associated with poor disease outcome, including functional ability and physical mobility. Thus, it is quite important for the physician to emphasize the association of smoking with poor disease prognosis in AS, and patients should be strongly recommended to avoid smoking cigarette.
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