Risk factors for in-hospital post-hip fracture mortality

Abstract

Introduction

Approximately 10% of hip fracture patients die during hospitalization; however, it is not clear what risk factors contribute to the excess mortality. This study sought to examine risk factors of, and to develop prognostic model for, predicting in-hospital mortality among hip fracture patients.

Methods

We studied outcomes among 410 men and 1094 women with a hip fracture who were admitted to a major-teaching-hospital in Sydney (Australia) between 1997 and 2007. Clinical data, including concomitant illnesses, were obtained from inpatient data. The primary outcome of the study was in-hospital mortality regardless of length of stay. A Log-binomial regression model was used to identify risk factors for in-hospital mortality. Using the identified risk factors, prognostic nomograms were developed for predicting short term risk of mortality for an individual.

Results

The median duration of hospitalization was 9 days. During hospitalization, the risk of mortality was higher in men (9%) than in women (4%). After adjusting for multiple risk factors, increased risk of in-hospital mortality was associated with advancing age (rate ratio [RR] for each 10-year increase in age: 1.91 95% confidence interval [CI]: 1.47 to 2.49), in men (RR 2.13; 95% CI 1.41 to 3.22), and the presence of comorbid conditions on admission (RR for one or more comorbid conditions vs. none: 2.30; 95% CI 1.52 to 3.48). Specifically, the risk of mortality was increased in patients with a pre-existing congestive heart failure (RR 3.02; 95% CI: 1.65 to 5.54), and liver disease (RR 4.75; 95% CI: 1.87 to 12.1). These factors collectively accounted for 69% of the risk for in-hospital mortality. A nomogram was developed from these risk factors to individualize the risk of in-hospital death following a hip fracture. The area under the receiver operating characteristic curve of the final model containing age, sex and comorbid conditions was 0.76.

Conclusion

These data suggest that among hip fracture patients, advancing age, gender (men), and pre-existing concomitant diseases such as congestive heart failure and liver disease were the main risk factors for in-hospital mortality. The nomogram developed from this study can be used to convey useful prognostic information to help guide treatment decisions.

Introduction

Hip fracture is one of the most serious consequences of osteoporosis, because it is relatively common in the elderly population, and is associated with increased risk of mortality [1], [2], [3]. Approximately 10% of women and 5% of men aged 60 years or above will sustain a hip fracture during their remaining lifetime [4]. Several studies have shown that approximately 20% of women and 30% of men die in the first year following a hip fracture [2], with men having a higher risk of mortality than women [5]. Worldwide, approximately 1.6 million hip fractures occur in elderly men and women each year, making it one of the most important public health burdens in the world [6].

Virtually all patients with hip fracture are hospitalized. A recent meta-analysis has suggested that the risk of mortality during the first 3 months after a hip fracture (including during hospitalization) is highest, with men having greater risk than women [7]. Indeed, the risk of in-hospital mortality has been estimated to range between 4 and 12% [5], [8], [9], [10]. However, it has not been clear which risk factors are associated with increased risk of in-hospital mortality. While pre-existing co-morbidity seems to be associated with increased risk of post hip-fracture mortality [9], [11], [12], its relative importance in the prognosis of in-hospital mortality has not been documented.

Knowledge of risk factors for mortality in hip fracture patients during hospitalization is critically important, because such knowledge can be translated into prognostic information, which can help allocate clinical care resources and risk counseling for patients and their relatives. Such knowledge can also help identify high-risk patients for early intervention to reduce their risk of death after hospital discharge. The present study sought to examine risk factors, and to develop a prognostic model for predicting absolute risk of in-hospital mortality among hip fracture patients.