Association of obesity with inflammation, disease severity and cardiovascular risk factors among patients with ankylosing spondylitis

Aim: To investigate total and central obesity in ankylosing spondylitis (AS), and assess the association with inflammation, disease severity and cardiovascular risk factors.

Methods: There were 105 AS patients enrolled. Anthropometry was measured to determine total (body mass index [BMI]) and central obesity (waist circumference [WC], waist-to-height ratio [WHtR]). We evaluated patients' disease activity, functional ability, global assessment, physical mobility, radiographic damage and health index. Erythrocyte sedimentation rate, C-reactive protein (CRP) and blood biochemistry profile were tested. Retrospective radiographic change was assessed in 39 patients. Presence of diabetes and hypertension were examined.

Results: The obese AS patients had higher inflammation (CRP), disease activity (Ankylosing Spondylitis Disease Activity Score [ASDAS] - CRP), physical mobility (Bath Ankylosing Spondylitis Metrology Index [BASMI]), radiographic damage (modified Stoke Ankylosing Spondylitis Spinal Score [m-SASSS]), liver function and blood pressure (all P < .05). Obesity (BMI, WC, WHtR) positively correlated with inflammation (CRP), physical mobility (BASMI), radiographic damage (m-SASSS), health index (Assessment of SpondyloArthritis International Society Health Index), liver function and blood pressure (all P < .05). Moreover, presence of central obesity (WC, WHtR) had correlation with disease activity (ASDAS-CRP) (r = .218, P = .027; r = .221, P = .025), and predicted longitudinal radiographic change (m-SASSS) (standard coefficient = 0.300, P = .041; standard coefficient = 0.288, P = .045). Importantly, central obesity was better in predicting high inflammation, disease activity, physical mobility, radiographic damage and health index in AS, and WHtR was the best for predicting m-SASSS (area under the curve = 0.734, P < .001). Obesity was associated with increased risk of diabetes and hypertension in AS.

Conclusion: Obesity was associated with higher inflammation, disease activity, physical mobility, radiographic damage, health index, liver function and cardiovascular risk factors in AS. Central obesity could predict a patient's longitudinal radiographic change. Central obesity is a useful predictor for high disease severity in AS.

Keywords: ankylosing spondylitis; cardiovascular risk; central obesity; inflammation; radiographic damage.