Age and clinical outcomes after hip fracture surgery: Do octogenarian, nonagenarian and centenarian classifications matter?

Background: older patients with hip fractures are arbitrarily classified as octogenarians, nonagenarians and centenarians. We have designed this study to quantify in-hospital mortality and complications among each of these groups. We hypothesised that the associations between age and in-hospital mortality and complications are continuously increasing, and that these risks increase rapidly when patients reach a certain age. Methods: this research is a retrospective cohort study using nationwide database between 2010 and 2018. Patients undergoing hip fracture surgery, and aged 60 or older, were included. The associations between patient age, in-hospital mortality and complications were visualised using the restricted cubic spline models, and were analysed employing multivariable regression models. Then, octogenarians, nonagenarians and centenarians were compared. Results: among a total of 565,950 patients, 48.7% (n = 275,775) were octogenarians, 23.0% (n = 129,937) were nonagenarians and 0.7% (n = 4,093) were centenarians. The models presented three types of association between age, in-hospital mortality and complications: (i) a continuous increase (mortality and respiratory complications); (ii) a mild increase followed by a steep rise (intensive care unit admission, heart failure, renal failure and surgical site hematoma) and (iii) a steep increase followed by a limited change (coronary heart disease, stroke and pulmonary embolisms). Conclusion: we identified three types of association between age and clinical outcomes. Patients aged 85-90 may constitute the upper threshold for age categorisations, because the risk of in-hospital complications changed dramatically at that stage. This information can improve clinical awareness of various complications and support collective decision-making.