Carotid intima-media thickness and paraoxonase activity in patients with ankylosing spondylitis

Purpose The risk of atherosclerosis is increased in several rheumatological disorders, but any such risk remains unproven for ankylosing spondylitis. Since carotid intima-media thickness is an indicator of early atherosclerosis, and the paraoxonase (PON1) enzyme has antioxidant activity to prevent LDL oxidation, we aimed to identify: 1) the relationship between carotid intima-media thickness (CIMT) and serum paraoxonase (PON1) activity in ankylosing spondylitis (AS) patients; and 2) the possible differences in CIMT in AS patients versus age-matched, healthy controls. Methods Forty-five AS patients (36.8±9.8 years, 36 males, 9 females) and 30 controls (35.9±10.2 years, 23 males, 7 females) were recruited consecutively. Serum PON1 activity and CIMT were measured. The Bath Ankylosing Spondylitis Metrology Index (BASMI), Bath Ankylosing Spondylitis Functional Index (BASFI), Bath Ankylosing Spondylitis Radiologic Index (BASRI) and Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) were used to identify relationships between these clinical indices and levels of CIMT and PON1. Results Mean CIMT was significantly increased in AS patients relative to controls (0.49±0.06 mm vs. 0.59±0.07 mm; p < 0.0001). Conversely, serum PON1 activity was decreased (199.1±60.3 U/L vs. 96.7±29 U/L; p < 0.0001). PON1 activity was negatively correlated with CIMT (r = -0.557, p = 0.0001). Disease duration was positively correlated with CIMT (r = 0.542, p = 0.0001) and negatively correlated with PON1 (r = -0.649, p = 0.0001). On multivariate analysis, disease duration and serum PON1 activity were found to be independent predictors of CIMT (R2 = 0.687, p = 0.0001). Conclusions In conclusion, significantly increased CIMT and decreased PON1 activity suggest a relationship between atherosclerosis and AS: a relationship that is strongly correlated with disease duration.