Background and Objective: Diffuse idiopathic skeletal hyperostosis (DISH) is characterized by ossification and calcification of paravertebral ligaments and peripheral entheses. DISH is associated with metabolic risk factors such as obesity, type 2 diabetes mellitus, hyperlipidemia, and hypertension. Ankylosing spondylitis (AS) is an additional enthesitis based disease of which obesity is a known feature.
Visceral adipose tissue (VAT) is a hormonally active component of total body fat, that influence several normal and pathological processes. Abnormally high deposition of visceral adipose tissue is known as visceral obesity. This body composition phenotype is associated with medical disorders such as metabolic syndrome, cardiovascular disease and several malignancies. Currently, the gold standard for the quantitative assessment of visceral adipose tissue is CT and MRI.
We aimed to evaluate whether DISH subjects would differ in their visceral adiposity composition from healthy age and gender matched controls and also from AS patients and by this may have a potential role as a surrogate marker for metabolic syndrome in DISH.
Methods: Archived records of 43 DISH subjects (male/female (M/F): 29/14, mean age: 71.74±7.35 years) (Resnick radiographic criteria) and 23 AS patients (M/F: 29/2, mean age:56.1±16.54 years) (Modified New-York Criteria) that had an abdominal CT were included in the study. 43 age- and gender-matched controls (M/F: 27/15, mean age: 72.71 ±8.59 years) with whole spine (to exclude DISH) and abdominal CTs were included. Subcutaneous adipose tissue (SAT) and VAT areas were measured on mid- L3, L4, L5 levels (GE AW server). The average VAT, SAT and VAT/SAT in each level was compared between all groups. Multivariate analysis (ANOVA) was used to eliminate effect of age differences between subjects.
Results: Average VAT was significantly larger in DISH subjects compared to healthy controls on all 3 levels (L3: 24.34 vs 18.43 mm2, P<0.05; L4:23.85 vs 18.05 mm2, P<0.05; L5: 19.09 vs 14.24 mm2, P<0.05). This did not change after correction for age. Average VAT/SAT on L3 vertebral level was also significantly larger in DISH compared to controls (1.26 vs 1.01, P<0.05). No significant difference was seen between average VAT of DISH and AS subjects.
Conclusion: Visceral adiposity, a known marker for obesity was significantly higher in DISH subjects compared to controls substantiating it as a potential surrogate marker for metabolic syndrome. No such difference was detected between DISH and AS, despite significant age differences of these two groups, suggesting a potential shared pathogenic pathway for these two diseases.
