Obesity Impairs TNF Inhibitor Responses in Axial Spondyloarthritis Save

Investigators with the Swiss Clinical Quality Management (SCQM) program have studied the effects of obesity on patients with axial spondyloarthritis (axSpA) and, specifically, their response to tumor necrosis factor inhibitors (TNFi).

A total of 624 axSpA patients starting a first TNFi and who met ASAS criteria for axSpA were enrolled and followed for 1 year. Patients were categorized according to their BMI and included 332 patients with normal (BMI 18.5 to 25), 204 patients who were overweight (BMI 25–30), and 88 obese (BMI >30) patients.

Obese individuals were older, had higher BASDAI levels, and had a more important impairment of physical function in comparison to patients of normal weight, while ASDAS and CRP levels were comparable between the three BMI groups.

After controlling for age, sex, HLA-B27, axSpA type, BASDAI, BASMI, CRP, smoking, enthesitis, physical exercise, and co-medications (DMARD, NSAIDs) in multiple adjusted logistic regression analyses were performed. 

Better ASAS40 responses were seen in normal weight (44%) patients compared to overweight (34%) or obese (29%) patients (overall p = 0.02).

Significantly lower odds ratios (ORs) for achieving ASAS40 response were seen in obese patients versus patients with normal BMI (OR 0.27, 95% confidence interval (CI) 0.09–0.70).

The respective adjusted ASAS40 OR in overweight versus normal weight patients was 0.62 (95% CI 0.24–1.14). Comparable results were found for the other outcomes assessed.

These data mirror that seen in other diseases - notably rheumatoid arthritis, psoriatic arthritis and juvenile idiopathic arthritis. Obesity is a significant risk factor for nonresponse. Moreover, weight reduction and management should be an important intervention when treating all patients with inflammatory arthritis. 

Yet there's good data that obesity, diet and exercise are often not addressed in the care of such patients.