POS0868 NOT ALL SYNDESMOPHYTES ARE EQUAL: THE IMPACT OF BODY MASS INDEX ON THE PRESENCE, LOCATION AND TYPE OF SYNDESMOPHYTES IN PATIENTS WITH AXIAL SPONDYLOARTHRITIS

Abstract

BackgroundNew bone formation is a hallmark of Axial spondyloarthritis (axSpA). Body mass index (BMI) is associated with the presence of syndesmophytes, especially in males. To date, it is not clear whether obesity impacts the axSpA through adipokines or biomechanical forces.ObjectivesWe aimed to investigate the relation between BMI and the presence and types of syndesmophytes at different spine levels, to better understand the impact of biomechanical forces in AxSpA.MethodsAxSpA patients who had cervical and lumbar spine x-rays as their standard of care were included (n=144). The cervical and lumbar spine xrays were scored separately, for the presence and type (thin vs bulky) of syndesmophytes. The factors associated with syndesmophytes were investigated, using a multivariate logistic regression.ResultsThe mean±SD age of the patients was 45.2±14.0. Syndesmophytes were seen in 48 (33.3%) patients of the cervical and 43 (29.9%) of the lumbar spine. Older and male patients had more frequent syndesmophytes on both levels. While the BMIs of patients with lumbar syndesmophytes were higher than those without (28.4 (8.2) vs 26.8 (7.0), p=0.015), patients with and without cervical syndesmophytes had similar BMIs (27.1 (8.3) vs 28.2 (7.5), p=0.177). Patients with cervical syndesmophytes had higher frequency of uveitis (47.9% vs 20.8%, p=0.001) than those without, which could not be detected for lumbar syndesmophytes.In regression analysis, age and male gender were associated with syndesmophytes in both the cervical and lumbar spine, whereas uveitis was associated only with syndesmophytes in the cervical spine (Table 1). BMI was associated only with syndesmophytes in lumbar spine, but not the cervical spine. The only factor that was found to be associated with bulky (vs thin) syndesmophytes was BMI for the lumbar spine, but not for the cervical spine (Table 1). Presence of PsA was not linked to the bulky type syndesmophytes.ConclusionHigher BMI increases the risk of syndesmophytes in the lumbar spine as well as impacting its shape; but not in the cervical spine. Abdominal obesity (apple-shaped) is more common among men in general. We hypothesize that the obesity may be increasing the risk of lumbar syndesmophytes as well as bulkiness in males due to the mechanical forces, which may not be seen in generally “pear-shaped” women, where the fat tissue and mechanical forces spare the lumbar spine.ReferencesNIL.Table 1.Multivariate logistic regression for the presence and type of syndesmophytesIndependent variablesPresence of Cervical syndesmophytesPresence of Lumbar syndesmophytesAllMaleFemaleAllMaleFemaleAge1.06 (1.03-1.10)***1.08 (1.03-1.14)+++1.06 (0.99-1.14)1.05 (1.02-1.09)*1.05 (1.00-1.09)###1.06 (0.97-1.15)Sex (male)3.80 (1.43-10.15)++--4.95 (1.72-14.22)**--BMI1.04 (0.96-1.13)0.99 (0.87-1.13)1.08 (0.95-1.22)1.12 (1.02-1.20)#1.16 (1.00-1.34)+1.09 (0.96-1.23)Smoking (ever)0.89 (0.36-2.22)0.56 (0.16-1.92)1.36 (0.28-6.69)0.86 (0.34-2.15)0.44 (0.13-1.50)1.36 (0.21-8.92)Uveitis (yes)4.75 (1.82-12.43)***6.97 (1.91-25.47)**3.82 (0.69-21.06)0.65 (0.24-1.79)1.29 (0.39-4.30).000 (.000-.)Elevated ESR (a)1.96 (0.75-5.13)1.05 (0.28-3.97)2.82 (0.53-15.03)2.29 (0.89-5.90)1.81 (0.54-6.12)3.86 (0.61-24.38)Proportion of exposure to biologics (b)1.01 (0.99-1.02)0.99 (0.97-1.01)1.02 (0.998-1.04)0.99 (0.98-1.01)0.98 (0.96-1.01)1.00 (0.98-1.03)Independent variablesPresence of bulky-shaped syndesmophytes in cervical spinePresence of bulky-shaped syndesmophytes in lumbar spineAge0.996 (0.94-1.06)1.01 (0.93-1.09)Sex (male)1.59 (0.34-7.39)1.53 (0.29-7.95)BMI1.09 (0.97-1.23)1.17 (1.02-1.34)##PsA Diagnosis2.00 (0.50-8.00)2.06 (0.45-9.37)Uveitis (yes)0.67 (0.17-2.62)-*p=0.005; **p=0.003; ***p=0.001;#p=0.017;##p=0.030;###p=0.042;+p=0.045;++p=0.008;+++p=0.002Numbers are given as OR (95%CI)(a) ESR elevated in at least two occasions (positive)(b) years on biologic therapies/total disease duration x100Acknowledgements:NIL.Disclosure of InterestsNone Declared.