Impact of diabetes on the risk of subsequent fractures in 92,600 patients with an incident hip fracture: A Danish nationwide cohort study 2004–2018

We investigated the incidence rates of a subsequent hip fracture (HF) and other subsequent fractures than HF after first incident HF, comparing patients with and without diabetes. Using Danish medical databases, we identified 92,600 incident HF patients in the period 2004–2018. Diabetes exposure was examined overall, by type of diabetes (T2D and T1D), and by presence of diabetes complications. We estimated cumulative incidence of subsequent HFs and fractures other than HF within two years of the incident HF. Using Cox regression, adjusted hazard ratios (aHRs) with 95 % confidence interval (CI) were calculated. Among incident HF patients, 11,469 (12 %) had diabetes, of whom 10,253 (89 %) had T2D and 1216 (11 %) had T1D. The 2-year incidence rates for a new subsequent HF were 4.8 % (95 % CI: 4.6–4.9) for patients without diabetes (reference group), 4.1 % (95 % CI: 3.8–4.6) for T2D, and 4.3 % (95 % CI: 3.3–5.6) for T1D. Corresponding aHRs were 1.01 (95 % CI 0.90–1.14) for T2D and 1.17 (95 % CI 0.87–1.58) for T1D. There was effect modification by sex, as women with T1D had an aHR of 1.52 (95 % CI: 1.09–2.11) for subsequent HF, and by specific diabetes complications (for example, patients with T2D and prior hypoglycemia had an aHR of 1.75 (95 % CI: 1.24–2.42) for subsequent HF, while patients with T1D and neuropathy had an aHR of 1.73 (1.09–2.75), when compared with patients without diabetes). For fractures other than HF, the 2-year incidence rates were 7.3 % (95 % CI: 7.2–7.5) for patients without diabetes, 6.6 % (95 % CI: 6.1–7.1) for T2D, and 8.5 % (95 % CI: 7.0–10.1) for T1D, with corresponding aHRs of 1.01 (95 % CI 0.92–1.11) for T2D and 1.43 (95 % CI: 1.16–1.78) for T1D. T2D was only a risk factor for other subsequent fractures among HF patients of high age (age 86–89 years: aHR 1.22 (95 % CI 0.99–1.55), age 90+ years: aHR 1.37 (95 % CI 1.08–1.74)), whereas T1D was robustly associated with increased risk of fractures other than HF in all subgroups. Among HF patients, we found no strong overall association of T2D or T1D with increased risk of subsequent HF, but diabetes patients with prior hypoglycemic events or neuropathy were at increased risk. In contrast, patients with T1D had a clearly increased risk of subsequent fractures other than HF.