Effect of Dementia on Postoperative Mortality in Elderly Patients with Hip Fracture

Background: The aim of this study was to assess the prevalence of dementia as an underlying disease in elderly patients with hip fracture, to investigate the effect of dementia on postoperative mortality after surgery of hip fracture, and to analyze the differences in postoperative mortalities according to the severity of dementia through subgroup analysis. Methods: This study selected 2,346 elderly patients who were diagnosed with unilateral intertrochanteric or femoral neck fractures who underwent surgery between January 2004 and December 2018. The patients were classified into the non-dementia group (2,196 patients) and dementia group (150 patients; no-medication [66 patients] and medication [84 patients] subgroups). The cumulative crude mortality rate was calculated, and 30-day, 60-day, 3-month, 6-month, and 1-year mortality rates were compared between the groups. A univariate regression test was performed using age, sex, diagnosis, surgery type, and Charlson's comorbidity index (CCI), as these variables had Pvalues of < 0.10. Multivariate regression analysis was performed to identify independent risk factors associated with mortality. Results: The 30-day, 60-day, 3-month, 6-month, and 1-year postoperative cumulative mortality rates were 1.8%, 3.8%, 5.6%, 8.9%, and 13.6%, respectively, in the non-dementia group, and 2%, 7.3%, 14%, 19.3%, and 24%, respectively, in the dementia group (P = 0.748, P = 0.048, P < 0.001, P < 0.001, and P = 0.001). The factors that affected the 1-year mortality were age (odds ratio [OR], 1.06; 95% confidence interval [CI], 1.02-1.08; P < 0.001), sex (OR, 2.68; 95% CI, 2.07-3.47; P < 0.001), CCI (OR, 1.34; 95% CI, 1.23-1.47; P < 0.001), and dementia (OR, 1.70; 95% CI, 1.46-1.08; P = 0.016). In subgroup analysis, severity of dementia influenced the 6-month mortality (OR, 1.41; 95% CI, 1.70-2.01; P = 0.018), and 1-year mortality (OR, 1.30; 95% CI, 1.17-1.90; P = 0.027). Conclusion: In elderly hip fracture patients, the comparison between patients with and without dementia revealed that dementia was an independent risk factor for mortality at a minimum of 1 year of follow-up, and the severity of dementia in hip fracture patients was a risk factor for mortality within 6 months and 1 year, postoperatively.