Association of obesity and nutritional status on early sepsis-associated acute kidney injury in older patients with sepsis

BACKGROUND: Despite numerous studies have examined the impact of obesity and poor nutritional status on the prognosis of critically ill patients, their relationship with sepsis-associated acute kidney injury (SA-AKI), particularly in older patients, remains unclear. This study aimed to investigate the association between obesity, nutritional status, and early SA-AKI in older patients with sepsis. METHODS: This retrospective cohort study utilized data from the Medical Information Mart for Intensive Care IV (MIMIC-IV) database. Older septic patients without pre-existing chronic kidney disease (CKD) stage 3-5 or elevated serum creatinine (SCr; >1.2 mg/dL in males and > 1.1 mg/dL in females) at admission were included to focus on incident early SA-AKI. Obesity was measured by body mass index (BMI), and nutritional status was evaluated using the Geriatric Nutritional Risk Index (GNRI) and Prognostic Nutritional Index (PNI) as prognostic indicators. Multivariable logistic regression, multivariable fractional polynomial regression, and restricted cubic spline models were applied to analyze the associations between BMI, GNRI, PNI, and early SA-AKI. Additionally, the relationships between BMI, GNRI, PNI and outcomes were examined in early SA-AKI patients. RESULTS: Among 4238 older septic ICU patients without pre-existing renal dysfunction, approximately 50% developed SA-AKI within 48 h of Intensive care unit (ICU) admission. Overweight (adjusted odds ratio [AOR] 1.39, 95% confidence interval [CI] 1.17-1.65), obese (AOR 1.95, 95% CI 1.63-2.35), and severely obese (AOR 2.19, 95% CI 1.63-2.94) were associated with higher odds of early SA-AKI risk compared with normal weight patients, while each 1-point increase in BMI raised risk of early SA-AKI by 4% (95% CI 1.03-1.05). No significant correlations were found between GNRI or PNI and early SA-AKI risk. Among older patients with early SA-AKI, underweight (In-hospital mortality: AOR 2.06, 95% CI 1.07-3.96; 6-month mortality: adjusted hazard ratio [AHR] 1.88, 95% CI 1.21-2.92) and lower GNRI (In-hospital mortality: AOR 1.80, 95% CI 1.00-3.22; 6-month mortality: AHR 1.38, 95% CI 1.06-1.81) predicted higher in-hospital and 6-month mortality. CONCLUSION: In a selected cohort of older septic ICU patients without pre-existing renal dysfunction, overweight and obesity are associated with a higher risk of early SA-AKI. Once SA-AKI develops, underweight and poorer nutritional status are related to worse survival. These findings highlight the prognostic value of BMI and nutritional indices for risk stratification in this population. Further prospective studies are warranted to validate these associations and explore their potential implications for risk stratification.