Malnutrition as a hidden driver of inpatient mortality in gastrointestinal cancer: A national analysis of the U.S. National Inpatient Sample, 2016–2023.

Abstract

e23235 Background: Inpatient mortality among patients with gastrointestinal (GI) malignancies remains high, yet risk stratification during acute hospitalization is limited. Malnutrition is frequently underrecognized in administrative data but may represent a marker of physiologic vulnerability. We evaluated the association between malnutrition and inpatient outcomes among hospitalized adults with GI cancer in the United States. Methods: We conducted a retrospective, survey-weighted analysis of the National Inpatient Sample (NIS), 2016–2023. Adult hospitalizations (≥18 years) with any-diagnosis GI malignancy (ICD-10-CM C15–C20, C22–C25) were included. Admissions with palliative care coding (Z51.5) were excluded. Malnutrition was defined using a narrow definition (E43, E44, E46) and a broad definition (E43, E44, E46, R64). The primary outcome was in-hospital mortality. Secondary outcomes included length of stay (LOS), hospitalization cost, acute kidney injury (AKI), shock, mechanical ventilation, dialysis, and discharge disposition. Survey-weighted regression models adjusted for demographics, payer, socioeconomic status, admission characteristics, hospital factors, cancer site, calendar year, and teaching status. Results: The analysis included 748,734 unweighted GI cancer hospitalizations after palliative exclusion. Malnutrition was present in 21.5% of admissions using the narrow definition and 22.8% using the broad definition. Crude inpatient mortality was higher among malnourished admissions (narrow: 4.96% vs 2.41%; broad: 5.21% vs 2.29%; both p < 0.001). Malnutrition was associated with longer LOS (9.27 vs 5.59 days), higher mean hospitalization costs ($31,904 vs $22,409), and increased rates of AKI (26.4% vs 17.3%) and shock (3.13% vs 1.61%). After adjustment, malnutrition remained independently associated with increased inpatient mortality (narrow: aOR 1.86, 95% CI 1.80–1.93; broad: aOR 2.05, 95% CI 1.98–2.12). In sensitivity analyses restricted to hospitalizations with a principal diagnosis of GI cancer, the association was stronger (aOR 2.15, 95% CI 2.01–2.31). Malnutrition was also independently associated with longer LOS (β +3.74 days, 95% CI 3.67–3.81) and higher costs (β 0.402, 95% CI 0.386–0.418), corresponding to an approximate 49.5% relative cost increase. Conclusions: Malnutrition is common among hospitalized patients with GI cancer and is independently associated with higher inpatient mortality, longer LOS, and increased resource utilization. These findings support malnutrition as an underrecognized marker of acute vulnerability and a potential target for inpatient risk stratification and quality improvement in GI oncology care.