Appropriate Anthropometric Indices for Geriatric Nutritional Risk Index in Predicting Mortality in Older Japanese Patients: A Comparison of the Lorentz Formula and Body Mass Index

Abstract

The Geriatric Nutritional Risk Index (GNRI) is a popular nutritional screening tool. However, the calculation of ideal body weight (IBW) differs among studies. We aimed to compare GNRI calculated using the Lorentz formula (LF) with a body mass index (BMI) and to investigate the cutoffs based on original or quartile criteria for the association with mortality in elderly patients in Japan. This retrospective study enrolled patients aged 65 and older in a long-term care hospital. The GNRI was calculated using two different IBW methods: the LF and a BMI of 22 kg/m². We categorized GNRI results based on the original criteria or quartile criteria. Mortality outcomes were analyzed using the GNRI based on IBW (LF or BMI) and its classification (original criteria or quartile) through Cox proportional hazard regression. There were 262 participants, including 160 women, with a median age of 86. There was a notable difference between GNRI-BMI and GNRI-LF. The GNRI-LF original and quartile criteria did not show an association with mortality. A significant association with mortality was found between Q1 and Q4 in the GNRI-BMI quartile criteria (hazard ratio: 2.60; 95% confidence interval: 1.66-4.07, p < 0.01), but not the GNRI-BMI original criteria. The GNRI calculated using BMI with quartile criteria proved to be a reliable predictor of mortality for Japanese elderly inpatients. The calculation method of GNRI and the appropriate cutoff point should be considered based on the patient’s background.