CRP and rheumatoid arthritis: In the comparison between patients with and without the aggravation of SAS, those with SAS aggravation tended to have an older age (p = 0.073)—notably ≥ 65 years (p = 0.017), longer RA duration (p = 0.044), higher CRP level at baseline (p = 0.133)—especially ≥ 3.8 mg/dL (p = 0.045) and > 1.0 mg/dL (p = 0.003), higher frequency of previous joint surgery (p = 0.008), corticosteroid administration (p = 0.006), Steinbrocker stages III–IV or mutilating changes (p = 0.015), and larger C2–C7 angle (p = 0.073) at baseline.