Association between fasting glucose levels and adhesive capsulitis in a normoglycemic population: a case-control study

Abstract

Background: Hyperglycemia is the most commonly cited risk factor for adhesive capsulitis. However, no study has established whether fasting glucose levels within the normoglycemic range are associated with idiopathic adhesive capsulitis (IAC). This study hypothesized that increments of fasting glucose levels within the normoglycemic range would be linked to IAC. This study investigated any association between normoglycemic fasting glucose levels and IAC.

Methods: This case-control study comprised a group of 151 patients with IAC without intrinsic shoulder lesions, extrinsic causes, or known metabolic risk factors such as diabetes, dyslipidemia, and thyroid dysfunction. The control group comprised 453 age- and sex-matched persons seeking general check-ups at the authors' health promotion center during the same period as the case group. Control subjects had normal shoulder function, no previous diagnosis of adhesive capsulitis or of metabolic disease, and no history of trauma or of shoulder surgery. The studied variables were body mass index, serum lipid profiles, thyroid hormone levels, fasting glucose levels, glycosylated hemoglobin A1c, and high-sensitivity C-reactive protein. Fasting glucose levels were studied as scale data and categorical data (<85, 85-89, 90-94, and 95-99 mg/dL). Multivariable conditional logistic regression analysis evaluated the matched sets of subjects. Odds ratios and 95% confidence intervals were determined for various potentially associated factors.

Results: Fasting glucose level, hypercholesterolemia, and high-sensitivity C-reactive protein were significantly associated with IAC (P ≤ .030). Fasting glucose levels in the <85 mg/dL quartile were significantly negatively associated with IAC (P ≤ .001). In contrast, fasting glucose levels in the 90-94 mg/dL quartile or higher were significantly positively associated with IAC (P ≤ .034).

Conclusion: IAC is positively associated with fasting glucose levels of 90-99 mg/dL, which are currently considered normoglycemic.

Keywords: Frozen shoulder; adhesive capsulitis; fasting glucose level; normoglycemic range; risk factors.