DISCUSSION
The present study was conducted to assess the prognostic utility of GNRI
in patients with aspiration pneumonia, mainly comprising older
individuals. Multivariate analysis revealed that male sex, a history of
CHF and malignancy, disease severity evaluated using the A-DROP scoring
system, lower GNRI score, and an initial antibiotic change were negative
prognostic factors. To the best of our knowledge, this is the first
study demonstrating the prognostic value of GNRI in patients with
aspiration pneumonia.
Aging is an irreversible biological process characterized by decreased
organ system reserve and weakened homeostatic
control.20 In older adults, these changes may lead to
decreases in food intake and absorption caused by impaired
gastrointestinal function, resulting in undernutrition. Furthermore,
underlying disease and inadequate dietary habits may negatively affect
nutritional status. Consequently, undernutrition leads to decreased
activity and weakened immune function, resulting in the further
deterioration of organ function and nutritional
status.21 Undernutrition is associated with weakening
of swallowing muscles and skeletal muscles and is a significant risk
factor for aspiration
pneumonia.6, 21Several studies have reported the utility of serum albumin levels and
BMI as prognostic factors for older patients with
pneumonia.23-26 Nevertheless, despite the ease of
evaluating these indicators, they may be influenced by various factors.
This study demonstrated that lower GNRI was a significant prognostic
factor for older patients with aspiration pneumonia. GNRI is calculated
based on serum albumin levels and a physique-based index. This
nutrition-related index is easily assessed without the need for complex
procedures such as the measurement of grip strength or limb
circumference. Our ROC analysis indicated that the AUC value for GNRI
was greater than that for albumin and BMI, and a significant difference
was observed with albumin. Serum albumin is affected by extracellular
fluid volume, dehydration status, and inflammatory
dynamics.27 BMI, a physique-based index, is also
affected by recent dehydration status. Thus, GNRI, which is derived from
serum albumin levels, height, and body weight, may have optimized the
deviation caused by these factors.
Recent studies have highlighted the prognostic significance of GNRI in
various diseases. According to seminal reports, GNRI < 98 was
defined as nutrition risk.10 In our cohort, more than
70% of patients had GNRI < 98 (even in the survivor group),
suggesting that most patients with aspiration pneumonia in our cohort
were at nutritional risk. Thus, establishing a cut-off value for GNRI in
patients with aspiration pneumonia is critical and warrants resolution.
The multivariate analysis revealed several independent prognostic
factors other than GNRI, including male sex, CHF, history of malignancy,
and higher A-DROP score. CHF is a risk factor for hospitalization with
pneumonia.28 In patients with heart failure, alveolar
flooding may disrupt immune function in the alveoli, including effective
opsonization and macrophage function, consequently affecting microbial
clearance and increasing the risk of pneumonia.29 In
addition, patients with impaired cardiac function may fail to meet the
increased demand for cardiac output owing to hemodynamic changes
associated with pneumonia.30 A current or latent
history of malignancy can adversely affect the clinical course of
patients with aspiration pneumonia. Cancer-related inflammation causes
exhaustion, which leads to undernutrition and inactivity. Systemic
cytotoxic chemotherapy or radiotherapy may attenuate immunity owing to
impaired bone marrow function, dysfunction of immunocytes, and prolonged
gastrointestinal dysfunction. The prognostic utility of scoring systems
such as CURB-65, A-DROP, and pneumonia severity index for older patients
with pneumonia remains controversial owing to heterogeneity in older
adults.31-33 These scoring systems comprise age,
gender, vital signs, laboratory findings, and comorbidities but lack
nutritional indicators. Moreover, an initial antibiotic change may
represent treatment failure and/or lead to the development of side
effects. Though dissecting this factor is challenging, an initial
antibiotic change may lead to prolonged treatment duration and result in
further deterioration in general condition and patient outcomes. As
stated above, similar to previous reports, we conjectured that the
prognostic evaluation of older patients with aspiration pneumonia
requires comprehensive assessments of patient status, disease severity,
and microbiological and/or antibiotic components.
This study had some limitations. First, this was a retrospective study
at a single institute. Patient characteristics and backgrounds may
differ between countries and/or local regions. Thus, the
generalizability of our findings to other populations may be limited.
Second, the diagnosis of aspiration pneumonia was conducted based on
clinical symptoms, test results compatible with pneumonia, and findings
regarding aspiration assessed by the ST and trained nurse. Given the
lack of consensus on diagnostic criteria for aspiration pneumonia, this
issue warrants further discussion. Third, this study did not precisely
investigate the cause of death, which may include mortality events other
than aspiration pneumonia. Notably, unlike CAP in younger patients, some
patients developed aspiration pneumonia in the course of senility and
exhibited fatal outcomes. Despite these limitations, this study employed
a relatively large sample size compared with previous studies on
patients with aspiration pneumonia.
In conclusion, the assessment of nutrition, disease severity,
microbiological findings, and antibiotic factors in older patients with
aspiration pneumonia is crucial for predicting prognosis. In particular,
GNRI is easy to calculate and may have a greater prognostic value than
conventional nutritional indicators. Further investigations are
warranted to validate the results of the present study.