Obesity may contribute to worse disease outcomes in axial spondyloarthropathy

SAN DIEGO – High BMI may be an independent predictor of worse disease outcomes and increased comorbidity among patients with axial spondyloarthropathy, according to findings presented at the American College of Rheumatology Annual Meeting.

“Obesity has been shown to have a negative impact on rheumatological conditions. For example, patients with arthritis who are obese have worse disease outcomes,” Gillian Fitzgerald, MD, Rheumatology Specialist Registrar at St. James’s Hospital in Dublin, Ireland, said in a press conference. “However, the literature looking at BMI and axial spondyloarthropathy is relatively sparse. Our study aimed to determine the prevalence of overweight and obesity in a large axial spondyloarthropathy cohort and to describe the association with disease outcomes.”

The patient population in this study was drawn from individuals in the Ankylosing Spondylitis Registry of Ireland. Patients undergo a standardized clinical assessment, which includes height and weight, and structured interviews are used to obtain patient-reported data. BMI is categorized according to WHO criteria, in which normal weight is classified as less than 25 kg/m² or less, overweight is classified as 25-29.9 kg/m² and obese is classified as greater than or equal to 30 kg/m².

As of June 2017, 683 patients had been regist. Most (n = 526; 77%) were male; the mean age was 45.9 ± 12.4 years. Mean duration of disease was 19 ± 12.2 years and mean delay to diagnosis was 8.6 ± 8.1 years. Modified New York criteria was satisfied in most patients (78.8%). Mean scores on the Bath Ankylosing Spondylitis Disease Activity Index, Bath Ankylosing Spondylitis Metrology Index, Bath Ankylosing Spondylitis Functional Index and Health Assessment Questionnaire were 3.9 ± 2.5, 3.6 ± 2.5, 3.6 ± 2.7 and 0.52 ± 0.52, respectively.

Mean BMI was 27.8 ± 5.3 kg/m². Most patients (38.9%; n = 252) were classified as overweight and 28.4% (n = 184) were classified as obese. Normal BMI was noted in 31.6% of patients (n = 205); approximately one percent of the cohort (1.1%; n = 7) was underweight.

Patients who were overweight or obese were “significantly older,” according to the study results. Longer disease duration and more comorbidities, particularly hypertension and hyperlipidemia, were reported in patients who were overweight or obese compared with patients of normal weight. In addition, disease activity was “significantly higher” among patients who were obese, and physical function, spinal mobility and quality of life was poorer for these participants when compared with both patients who were of normal weight and who were overweight.

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“There was no difference in the male-to-female breakdown in each category of BMI,” Fitzgerald said. “The prevalence of extra-articular manifestations – including, primarily, uveitis, psoriasis and inflammatory bowel disease – were equally distributed throughout the three weight groups. Unsurprisingly, the number of patients with comorbidities increased as BMI increased.”

BMI and obesity correlated with higher BASDAI, ASQoL, BASMI, BASFI and HAQ scores in univariable linear regression. Obesity continued to be an independent indicator of higher disease activity and poorer function in multivariable regression analysis.

However, the study did not analyze whether axial spondyloarthropathy prevented patients from exercising, and therefore contributed to increased weight, or if patients with increased weight were more likely to develop the disease.

“We can’t speculate about cause and effect,” Fitzgerald said. “We can only say that patients with axial spondyloarthropathy who are obese had worse disease outcomes. It’s hard to know which causes which. We need prospective studies that better explain cause and effect to see whether, if you implement weight loss strategies, you can improve disease outcomes.” – by Julia Ernst, MS

Reference:

Fitzgerald G, et al. Abstract 2508. Presented at: American College of Rheumatology Annual Meeting; Nov. 3-8, 2017; San Diego.

Disclosures: Fitzgerald reports an association with AbbVie. Please see the full study for a list of all other researchers’ relevant financial disclosures.