Are patients with newly diagnosed frozen shoulder more likely to be diagnosed with type 2 diabetes? A cohort study in UK electronic health records.

Aim: To estimate the association between newly diagnosed frozen shoulder and a subsequent diagnosis of type 2 diabetes in primary care.

Methods: We conducted an age-, gender- and practice-matched cohort study in UK primary care electronic medical records containing 31 226 adults diagnosed with frozen shoulder, matched to 31 226 without frozen shoulder. Patients with pre-existing diabetes were excluded. Variables were identified using established Read codes. A hazard ratio (HR) for the association between incident frozen shoulder and a subsequent type 2 diabetes diagnosis was estimated using shared frailty Cox regression, adjusted for age and gender. To determine whether the association could be explained by increased testing for type 2 diabetes based on other risk factors, a secondary analysis involved re-running the Cox model adjusting for the mean number of consultations per year, hyperlipidaemia, hypertension, obesity, thyroid dysfunction, ethnicity, deprivation, age, and gender.

Results: Participants with frozen shoulder were more likely to be diagnosed with type 2 diabetes (1559 out of 31 226 patients [5%]) than participants without frozen shoulder (88 out of 31 226 patients [0.28%]). The HR for a diagnosis of type 2 diabetes in participants with frozen shoulder versus people without frozen shoulder was 19.4 (95% confidence interval [CI] 15.6-24.0). The secondary analysis, adjusting for other factors, produced similar results: HR 20.0 (95% CI 16.0-25.0).

Conclusions: People who have been newly diagnosed with frozen shoulder are more likely to be diagnosed with type 2 diabetes in the following 15.8 years. The value of screening patients presenting with frozen shoulder for type 2 diabetes at presentation, alongside more established risk factors, should be considered in future research.