The relationship between the incidence of adhesive capsulitis and hemoglobin A_1c

Previous studies have shown no correlation between adhesive capsulitis and hemoglobin A_1c (HbA_1c). However, HbA_1c is only a measure of short-term blood sugar control. We created a previously nonvalidated variable, cumulative HbA_1c, that uses HbA_1c values over time to estimate the total disease burden a single individual experiences over a period. In this study, we aimed to evaluate whether a correlation exists between cumulative HbA_1c levels in diabetic patients and the prevalence of frozen shoulder. We hypothesized that poor long-term glucose control would be correlated with increased incidence of adhesive capsulitis.

A retrospective analysis at a single institution was performed. Data from all patients from a single institution with any HbA_1c values were collected. A total of 24,417 patients met the inclusion criteria. A variable was created establishing the cumulative magnitude of abnormal HbA_1c values over time, termed "cumulative HbA_1c." Logistic regression analysis was performed to determine whether long-term glucose control was predictive of the development of adhesive capsulitis.

Cumulative HbA_1c was positively associated with adhesive capsulitis (7.6 × 10^-5) (ie, odds ratio of 1.000076). The effect size of cumulative HbA_1c on adhesive capsulitis was significant; for each unit of time that the HbA_1c level was greater than 7, there was a 2.77% increase in the risk of adhesive capsulitis.

Cumulative HbA_1c was associated with an increased incidence of adhesive capsulitis. This finding suggests that the effects of diabetes that predispose patients to the development of adhesive capsulitis are dose dependent. Patients with worse blood sugar control over a longer period are at an increased risk of the development of adhesive capsulitis.