Obesity in adults with axial spondyloarthritis is associated with significantly worse scores on measures of disease activity when compared with normal-weight patients, according to findings from a meta-analysis of 10 studies.

Dr. Augusta Ortolan, University of Padova, Italy

Dr. Augusta Ortolan

Obesity or overweight could influence axial spondyloarthritis (axSpA) disease activity in several ways, including production of inflammatory mediators by adipose tissue, joint pain caused by excess weight, loss of muscle mass, and increased atherosclerosis, wrote Augusta Ortolan, MD, of the University of Padova (Italy), and colleagues.

However, “it is less clear whether overweight or obesity per se may be a cause of higher disease activity scores,” they added.

In a systematic review published in Arthritis Care & Research, the investigators identified 10 studies to use in the meta-analysis that involved associations between body mass index (BMI) and disease activity in adults with axSpA. The review included three cohort studies and seven cross-sectional studies of patients aged 18 years and older. Disease activity was assessed using the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) and the Ankylosing Spondylitis Disease Activity Score (ASDAS).

Overall, the mean difference in BASDAI between patients with normal BMI and overweight or obese patients was –0.38 (P < .0001), and the mean difference in ASDAS between the same groups was –0.19 (P < .0001). When separated into overweight and obese categories, only the difference between normal weight and obesity remained significantly associated with differences in scores on both measures (–0.78 and –0.42, respectively; P < .0001 for both measures). The difference in scores between normal-weight and overweight/obese patients increased with BMI categories, which suggests a possible “dose-effect” relationship between fat mass and disease activity, the researchers wrote.

The study findings were limited by several factors, including the lack of randomized, controlled trials, and potential bias and inconsistency involving BMI measurements, the researchers noted.

However, “we were able to mitigate such limitations via a strict methodology and consistency in the outcomes, thus allowing us to use mean differences – instead of standardized mean differences – as outcomes, which are much easier to interpret and can be directly related to the measurement unit of the outcome,” they wrote.

The results extend data from previous studies, which “could help interpret disease activity measures and understand the difference we could expect between an axSpA patient with normal BMI and increased BMI,” they concluded.

The study received no outside funding. The researchers had no financial conflicts to disclose.

SOURCE: Ortolan A et al. Arthritis Care Res. 2020 Aug 16. doi: 10.1002/acr.24416.