Background: Comprehensive evaluations of the nutritional parameters associated with length of hospital stay are lacking. We investigated the association between malnutrition and length of hospital stay in a cohort of ambulatory adult patients. Methods: From September 2006 to June 2009, we systematically evaluated 1274 ambulatory adult patients ad - mitted to hospital for medical or surgical treatment. We evaluated the associations between malnutrition and pro - longed hospital stay (> 17 days [> 75th percentile of distribution]) using multivariable log-linear models adjusted for several potential nutritional and clinical confounders re - corded at admission and collected during and at the end of the hospital stay. Results: Nutritional factors associated with a prolonged hospital stay were a Nutritional Risk Index score of less than 97.5 (relative risk [RR] 1.64, 95% confidence interval [CI] 1.31-2.06) and an in-hospital weight loss of 5% or greater (RR 1.60, 95% CI 1.30-1.97). Sensitivity analysis of data for patients discharged alive and who had a length of stay of at least three days (n = 1073) produced similar findings (adjusted RR 1.51, 95% CI 1.20-1.89, for Nutritional Risk Index score <97.5). A significant association was also found with in-hospital starvation of three or more days (RR 1.14, 95% CI 1.01-1.28). Interpretation: Nutritional risk at admission was strongly associated with a prolonged hospital stay among ambulatory adult patients. Another factor associated with length of stay was worsening nutritional status during the hospital stay, whose cause-effect relationship with length of stay should be clarified in intervention trials. Clinicians need to be aware of the impact of malnutrition and of the potential role of worsening nutritional status in prolonging hospital stay.
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