The Effect of Obesity in Individuals with Ankylosing Spondylitis: A Single Center Cohort Study

Abstract

Aim: The aim of this study was to compare the disease activity and functional status of individuals with Ankylosing Spondylitis (AS) according to body mass index (BMI). Material and Methods: This study, which was planned as a single-center cohort study, included 437 individuals with AS. Disease activities were evaluated with the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), and functional levels with the Bath Ankylosing Spondylitis Functional Index (BASFI). Participants were categorized in 3 groups according to BMI data based on the criteria of the World Health Organization: normal weight:20-24.9; overweight: 25-29.9; obese:≥30. One Way Anova Test, Kruskal Wallis Test, Mann Whitney U test and Chi-Square Test were used to compare independent group differences. Linear regression models were used to describe the relationship between BASDAI, BASFI (dependent variables) and BMI categories (independent variables). Univariate regression analyses were performed (only one independent variable in the model). Results: Among 437 patients with AS, 30.2% are normal weight, 39.5% are overweight and 30.2% are obese. Analysis results of data between BMI groups; significant difference was in BASFI (p=0.001) in favor of the obese group. In binary group comparisons for BASFI; there was a significant difference in favor of the obese group between normal and obese (p=0.002) and between overweight and obese (p=0.001). Obese was significantly associated with higher BASFI score compared to the normal weight group without adjustment for covariates (β:-0.37, 95%CI -0.66/-0.08, p=0.006). On the other hand, there was no association between BASDAI and obesity (β:-0.50, 95%CI -1.11/ 1.22, p:0.130). Conclusion: The BMI of Turkish AS individuals in a single center cohort had no effect on disease activity, but obesity had a worse effect on functional level.