SAN DIEGO – Among patients with axial spondyloarthropathy, higher BMI and obesity independently predicts worse disease outcomes, according to results from a registry study.
“Obesity is one of the biggest public health challenges facing us in the 21st century,” lead study author Gillian Fitzgerald, MD, said in an interview in advance of the annual meeting of the American College of Rheumatology.
“Traditionally, we have a perception of patients with axial SpA being of normal or even thin body habitus. However, recent studies have indicated that this is not the case and that obesity is prevalent in axial SpA patients. The negative consequences of obesity in the general population are well documented, with affected patients suffering greater morbidity and mortality.”
Dr. Fitzgerald, of St. James’s Hospital, Dublin, Ireland, noted that research to date in axial SpA indicates that disease outcomes may be worse in obese patients. However, existing literature looking at obesity in axial SpA is relatively sparse. In an effort to clarify this issue, she and her associates evaluated 683 patients from the Ankylosing Spondylitis Registry of Ireland (ASRI), which is designed to provide descriptive epidemiological data on the Irish axSpA population via standardized clinical assessments and structured interviews. The mean age of the 683 patients enrolled as of June 2017 was 46, the majority (77%) were men, their mean disease duration was 19 years, and their mean delay to diagnosis was nine years. Most (79%) fulfilled Modified New York modified criteria, their mean Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) was 3.9, their mean Bath Ankylosing Spondylitis Metrology Index (BASMI) was 3.6, their mean Bath Ankylosing Spondylitis Functional Index (BASFI) was 3.6 and their mean Health Assessment Questionnaire (HAQ) was 0.52.
Based on WHO criteria, the cohort’s mean BMI was 27.8 kg/m2. Of these, 38.9% were overweight and 28.4% were obese. “Indeed, only 32% of the cohort have a healthy BMI,” Dr. Fitzgerald commented. “When we looked at the relationship between BMI and disease outcomes, we found that obese patients had more severe disease than their normal weight and overweight counterparts, with higher measures of disease activity, quality of life, disability and function, as well as worse spinal mobility.”
The researchers also observed that the prevalence of smoking was lower in obese patients, compared with normal weight patients (18% vs. 38, respectively). In univariable linear regression, BMI and obesity were associated with higher BASDAI, BASMI, BASFI and HAQ scores. In multivariable regression analysis, only obesity remained an independent predictor of higher disease activity and worse function (P less than .01).
“As clinicians, we are always looking for ways to reduce the burden of disease that patients carry and to improve outcomes,” Dr. Fitzgerald said. “In this study, we demonstrated that over two-thirds of our axial SpA patients are either overweight or obese, and that these patients have more severe disease. Further research is needed to clarify this relationship between obesity and disease severity; in particular, the effect of losing weight on disease outcomes needs to be clarified. However, when devising treatment plans for axial SpA patients, this study provides rheumatologists with a strong rationale to include strategies to actively control weight.”
She acknowledged that the study’s cross-sectional design is a limitation. “This means cause and effect can’t be determined exclusively from this study; therefore, prospective studies are required to further clarify this relationship that we have noted between obesity and disease outcomes.”
ASRI is funded by an unrestricted grant from AbbVie and Pfizer. Dr. Fitzgerald disclosed having received research support from AbbVie.