Older patients hospitalized for traumatic injury have more complex and frequently unfavorable clinical courses than younger patients. In this large national dataset of hospitalized patients with moderate to severe traumatic injury, we found that nearly all infections in the post-injury hospital course, including pneumonia, abscess, wound infection, empyema, urinary tract infection, bacteremia, and aspiration pneumonia, were associated with at least double the risk of death for older versus younger patients. Certain non-infectious complications also were identified as associated with greater mortality among older patients, including failure of reduction/fixation, pressure ulcer, deep venous thrombosis, pneumothorax, pulmonary embolism, and compartment syndrome. Based on these age-related mortality differences, we developed a new outcome, mortality-associated geriatric complications (MGCs). By categorizing the level of pre-existing condition burden based on age, co-morbidity, and gender, we present a simple clinical nomogram () to identify risk of MGCs or death at the time of admission.
Our findings extend prior research on risk factors for traumatic injury and mortality15,19-26
by examining a broader outcome, MGCs, in relation to hospital mortality. Inpatient and post- surgical complications are the focus of increasing efforts to improve acute care outcomes11
and are associated with death27
, increased cost 28
, and length of stay.29,30
In our series, 14 % of all patients suffered at least one complication during hospitalization. Compared to younger patients, older patients had a staggering 34% risk of developing an MGC. Hospital complications are most likely the explanation of why older trauma patients that represent 13% of trauma admissions consume 25% of hospital resources.31
In a recent study of hospital complications of trauma injury, which focused on trends in prevalence with increasing age, Adams et al.9
found that infectious complications was less common above age 45, attributing this surprising finding to increasing difficulty of diagnosing infection in older patients. In a differing approach, we examined our patients' mortality risk in the presence of each specific complication and identified complications that posed the greatest risk among older adults. We found that older patients with infections are at the greatest risk of dying in relation to younger patients. While we recommend more empirical work in this area, both studies suggest that infection in older trauma patients should be a natural target for future hospital interventions such as early recognition, increased surveillance or preventive efforts.
This study extends prior research on co-morbidity that has focused on specific conditions and their independent contributions to mortality,23,32
and on age differences in co- morbidity risk in older patients.34
We instead focused on co-morbidities available to us in the NTDB and conceptualized patients' condition count as their overall burden of pre-existing disease. As expected, we found that co-morbidity contributes to risk of MGCs and death. We also found a steeper relationship between age and MGCs among patients with 3 or more pre- existing conditions compared to those with fewer conditions, with co-morbidity contributing increasing risk above the age of 45. This finding is in agreement with prior observations that mortality in trauma patients increases after the age of 45 years, suggesting a younger age definition for the geriatric population in trauma patients.9,12,13
Co-morbidity may be a partial explanation for this increase in risk.
We developed a nomogram () that can be used to stratify risk of death and MGCs based on age, gender, and a simple categorization of co-morbidity count. The potential broader impact of such risk stratification is better identification of aging trauma patients who have the most to gain from in-hospital preventive measures and targeted interventions. This can range from a systems-level approach to preventing the MGCs to a patient-level tool to tailor risk based on known information (age, gender, chronic conditions) at the beginning of the hospitalization, when preventive efforts can feasibly be implemented and be more effective. Such clinical risk tools are supported by current trauma guidelines in older patients.12,13
The nomogram we provide might be a starting point to prioritize scarce hospital services and preventive efforts for the individual patients at the greatest risk, e.g., intensified infection-prevention or mobility promotion interventions.
The main strength of this analysis is that we used a very large dataset representing all four geographic quadrants of the United States, spanning trauma centers from levels 1 through 3, with a wealth of data concerning age, co-morbidity, and hospital complications. Despite this vast advantage, we identified a number of limitations inherent to using the NTDB for outcomes research.
Current practice guidelines recommend against the use of injury severity indices in clinical care of individual patients because these are not known until discharge.12,13
We did not focus on small differences in ISS for this reason. However, because injury severity is such a strong predictor of death and complications in older hospitalized patients,4-10
injury severity was a necessary part of our study design. Our results should be interpreted in light of our study inclusion criteria of moderate-to-severe injury (ISS≥16, mean ISS=25). Even after limiting by injury severity, the older patients had a slightly lower ISS than the younger patients. Although this difference is likely not clinically relevant, we accounted for it by further controlling for ISS in the analyses. We speculate that the reason for the difference was that older patients are more likely to be hospitalized, and therefore, reported in the NTDB, than younger patients with the same ISS.
Another potential reason is that mechanism of injury differs between the two groups. Low-level falls and blunt injury were more common among the old despite removing low-severity injury from the sample. Future research is needed to develop ways that specific mechanisms of injury and simpler injury severity measures can be identified early in hospital course to stratify risk.
Our study has several additional limitations. The NTDB is a voluntary registry of hospitals, and not a population-based study, with known variation in reporting practices.14
We attempted to address potential bias against older patients' injuries using analytic weights. Additionally, some hospitals did not report complications or pre-existing conditions. Reporting differences have been shown to change ranking order of complication rates between facilities.16
Therefore, we only considered patients for complications based on facility-level reporting practice.16
Using similar logic, we approached multi-morbidity by limiting our analysis to facilities reporting multiple pre-existing conditions. The NTDB also does not include pre-injury functional status, an important geriatric screening tool that prospectively predicts development of hospital complications in older trauma patients.35
Finally, the MGCs we identified should be interpreted as having an association with, rather than cause of, increased mortality. In this retrospective dataset, it is possible that participating institutions were more likely to report infections among older patients who died. Therefore, future prospective and interventional studies focusing on infectious complications in older patients are needed. The risk nomogram that we developed may be useful in combination with screening for pre-injury functional impairment35
and physiologic parameters36
to identify older patients most vulnerable to a complex clinical course.
In summary, we found that older patients with certain specific complications are at differentially higher risk of death due to their age, even after controlling for other known risk factors. We present a risk nomogram to predict death and a new outcome, MGCs. Future work is needed to validate the nomogram prospectively and in population-based studies. The potential impact of this work will be a more efficient approach to the complex clinical needs of older trauma patients with multiple chronic conditions.