Pneumonia in hospitalized elderly hip fracture patients: the effects on length of hospital-stay, in-hospital and thirty-day mortality and a search for potential predictors

Background: Hip fracture in the elderly is associated with increased morbidity and mortality. Pneumonia during hospitalization is not uncommon and is associated with poorer outcomes, such as an increased risk of readmission and higher mortality rates. We aim to identify independent predictive factors for developing pneumonia during hospitalization in this group and also assessed the effect pneumonia has on hospital-stay, in-hospital and 30-day mortality. Methods: Retrospective cohort study with prospectively collected data from hospitalized elderly hip fracture patients between January 2015 and January 2017. Examined predictors were age, gender, pre-fracture living situation, pre-fracture mobility score, pre-fracture ADL-status, history of dementia, diabetes, congestive heart failure, chronic obstructive pulmonary disease and prior stroke, ASA-score, anemia at admission, surgery within 48 hours, surgical procedure and anesthesia used. Multivariable regression analysis including resampling methods (bootstrapping) was used to examine the effects of predictors. Results: Of 407 patients, 62 (15.2%) were treated for pneumonia during hospitalization. Only gender, surgery within 48 hours and history of COPD differed significantly at baseline between the groups with and without pneumonia. Adjusted for age and gender, we observed a 1.6 times longer hospital-stay (95% CI 1.4-1.9, p<0.001), higher in-hospital mortality (OR 8.0, 95% CI 2.97-22.29) and 30-day mortality (OR 3.22, 95% CI 1.44-6.94) in the pneumonia-group. Pneumonia explained 9.1% of the variance in the length of hospital-stay aside from age and gender. Eight candidate predictors from the univariate analyses with a p<0.20 were selected for a multivariable logistic regression in 1000 bootstrap samples. Gender and history of COPD were most often found to have a p<0.10 (61.3% and 58.2%, respectively) in the bootstrap analyses and more than 80% stability in their B-coefficient signs. The discriminative quality of these two variables alone resulted in an AUC of 61.7% (95% CI 54%-69%). Conclusion: Pneumonia resulted in longer hospital-stay and higher mortality rates. Of the 15 selected potential risk-factors for developing pneumonia during admission, male gender and history of COPD appeared to have the best potential as predictors. The other risk-factors had poorer performance, probably due to the few events and limited occurrence of some candidate variables in our study population.