Frailty is a concept proposed by Buchner and Wagner in 1992 and corresponds to a weakened mind and body due to aging [1]. People with frailty have a substantially increased risk of falls, disability, being bedridden, death, and various complications [2]. Thus, early intervention is needed [3].

Rheumatoid arthritis (RA) is an autoimmune disease that causes synovitis in the joints, resulting in joint deformity due to cartilage damage and bone destruction. RA patients suffer from joint pain and limited joint range of motion and are significantly impaired in activities of daily living. In recent years, advances in disease-modified antirheumatic drugs (DMARDs), including biologics and biosimilar/targeted synthetic DMARDs (b/ts-DMARDs), have reduced the number of patients with systemic joint deformity. Nevertheless, RA patients are more likely to become frailty due to joint deformation associated with local arthritis and muscle weakness than their healthy counterparts [4]. Given the high prevalence of RA (0.5–1.0% in many populations) [5], countermeasures against frailty are required for this patient population.

Japan is struggling with an aging and shrinking population and is one of the world's most rapidly aging societies [6]. Many older adults in Japan are pre-frail [7], and older RA patients are generally at a greater risk of frailty than the general population. Indeed, as the aging of the RA population progresses, the number of RA patients with frailty increases [8].

Against this backdrop, the present study aimed to investigate factors that predict frailty in RA patients. Focus was placed on pre-frail patients with RA because only a few prospective longitudinal studies have been conducted on this topic. Not surprisingly, pre-frail patients are more prone to frailty compared with robust patients in the short term. Thus, investigating pre-frail patients may provide insight into the mechanisms underlying the transition from pre-frail to frail status.