RA is a complex autoimmune disease resulting from apparently stochastic interactions between genetic and environmental factors. Important environmental factors include smoking, especially heavy smoking, which is the greatest lifestyle risk factor for the development of RA. Environmental factors implicated in addition to smoking include education/social class, breastfeeding, body fat, vitamin D levels, and caffeine and alcohol consumption. According to the WHO, worldwide obesity has nearly tripled since 1975. In parallel with its increase in the general population, obesity has become increasingly common in RA patients.
BMI has been the obesity measure of choice in many previous studies in inflammatory arthritis. However, it has been shown that BMI is not an accurate anthropometric method to diagnose obesity, especially in individuals with altered body compositions (such as inflammatory arthritis patients) due to its inability to discriminate between lean mass and fat mass. Waist circumference has been shown to be superior to BMI in its correlation with visceral fat and has become the preferred measure for abdominal obesity.Central obesity is defined as having a waist circumference of ≥94 cm in men and ≥80 cm in women The pro-inflammatory nature of fat tissue is now well established. These effects are mediated through the secretion of numerous pro-inflammatory cytokines by adipose tissue, coined adipokines. It is suggested that increased adiposity may have a role in the pathogenesis of inflammatory diseases, however the evidence is conflicting. Numerous studies have demonstrated a positive correlation between BMI and the risk of developing RA. An association between obesity and disease activity in RA has been reported in several previous studies. The Better Anti‐Rheumatic Farmacotherapy observational (BARFOT) study demonstrated that obese patients had higher disease activity and lower rates of remission). Obesity has also been associated with a reduced response to TNF-inhibitors (TNFi).
The aim of this study was to evaluate body composition in seropositive and seronegative rheumatoid arthritis (RA) and psoriatic arthritis (PsA) patients and assess associations with disease characteristics and baseline synovial arthroscopic findings. We will also access the effect of Obesity on immune cell responses.