Hospitalisation and subsequent fracture risk—a national matched cohort study in Denmark

In a national matched cohort study in Denmark, time-to-event analyses described binary and dose-response associations between hospitalisation and subsequent fracture events. Hospitalisation was confirmed as a risk factor for subsequent MOFs, with sex differences and dose-dependencies observed. Major osteoporotic fractures (MOFs) are a cause and, importantly, a consequence of hospitalisation. PURPOSE: Frailty and osteoporosis are risk factors of major osteoporotic fractures (MOFs) and associated mortality. Moreover, hospitalisation is associated with a subsequent increase in frailty, partly due to immobilisation. METHODS: This national matched cohort study was performed using Danish registry data available for individuals aged >45 years. Individuals with at least one day in hospital during 2023 were matched to controls using age, sex, and comorbidities. The end date of the last hospitalisation in 2023 was used as the start of follow-up. Days hospitalised in total, during the last hospitalisation, and the count of hospitalisations in an exposure window reaching 364 days past the last day of the last hospitalisation were collected for dose-response analyses. Cumulative incidence of MOF was estimated with a two-step adjustment for the competing risk of mortality, complemented by cause-specific Cox proportional hazards models adjusted for confounders. RESULTS: Hospitalisation was associated with a higher risk of MOF. The fully adjusted model showed a greater risk of MOF in the hospitalised sample at 14 days (HR: 1.77; 1.47-2.14), 30 days (HR: 1.28; 1.12-1.47), one year and complete follow-up (HR: 1.03 and 1.10, respectively). Females had consistently higher MOF rates and, in contrast to males, showed temporary normalisation of MOF cumulative incidence and cause-specific risk at 90 days (HR: 0.93; 0.84-1.03). Significant dose-response associations were reported for hospitalisation duration and count. CONCLUSION: There is a time-dependent sex-specific association between hospitalisation and MOF, supported by several dose-dependencies.