Chronic inflammation is implicated in the development of idiopathic adhesive capsulitis (IAC), whose association with high-sensitivity C-reactive protein (CRP), an inflammation marker, is undetermined. This study's purposes were to investigate the association between high-sensitivity CRP levels and IAC and to determine the metabolic factors associated with high-sensitivity CRP.This case-control study examined a group of 202 patients with IAC and without intrinsic shoulder lesions or extrinsic causes and a control group of 606 age and sex-matched persons seeking general check-ups at our health promotion center during the same period as the case group. Control subjects had normal shoulder function and no previously diagnosed adhesive capsulitis; no medication for diabetes, dyslipidemia, and thyroid abnormalities; and no history of trauma or of shoulder surgery. The studied variables were body mass index; diabetes; thyroid abnormalities; dyslipidemias; triglyceride/high-density lipoprotein (TG/HDL) >3.5; serum levels of thyroid hormone, fasting glucose, and glycosylated hemoglobin A1c (HbA1c); and high-sensitivity CRP >1.0 mg/L. Multivariable conditional logistic regression analysis evaluated the matched sets of subjects. Odds ratios (ORs) and 95% confidence intervals (CIs) were determined for the studied variables possibly affecting IAC.Serum high-sensitivity CRP >1.0 mg/L was significantly associated with IAC (OR, 2.47 [95% CI, 1.65 to 3.70]) after adjusting for diabetes, fasting glucose level, HbA1c, dyslipidemia, TG/HDL >3.5, and thyroid-stimulating hormone (p ≤ 0.031). Diabetes (OR, 1.71 [95% CI, 1.09 to 3.33]), fasting glucose level (OR, 1.54 [95% CI, 1.12 to 2.12]), HbA1c (OR, 2.00 [95% CI, 1.25 to 3.22]), hypertriglyceridemia (OR, 1.70 [95% CI, 1.03 to 3.41]), hypo-high-density lipoproteinemia (OR, 1.98 [95% CI, 1.04 to 3.79]), and TG/HDL >3.5 (OR, 1.37 [95% CI, 1.06 to 1.88]) were significantly associated with high-sensitivity CRP >1.0 mg/L in patients with IAC (p ≤ 0.039).Serum high-sensitivity CRP >1.0 mg/L is an independent associated marker for IAC. Dyslipidemia, insulin resistance, and hyperglycemia, which are recognized factors associated with IAC, are also associated with high-sensitivity CRP >1.0 mg/L in these patients, supporting the interaction of chronic systemic inflammation in IAC.Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.
