Beyond the MNA: A Biological Vulnerability Phenotype Associated with Prolonged Hospitalization in Older Adults

Nutritional status in hospitalized older adults is usually evaluated using screening tools such as the Mini Nutritional Assessment (MNA). During acute illness, however, these tools may overlook biologically relevant vulnerability related to inflammation and metabolic stress, a condition often described as occult malnutrition. The clinical implications of applying a more stringent biological definition of this phenotype are still poorly defined.

We conducted an observational cohort study including 172 hospitalized older adults (mean age 86.7 ± 6.0 years) in an acute geriatric setting with complete data on MNA, serum albumin, hemoglobin, and C-reactive protein (CRP). Occult malnutrition was defined by the coexistence of at least two abnormal biological markers: hypoalbuminemia (albumin < 3.5 g/dL), anemia (Hb < 12 g/dL), and elevated CRP (>0.5 mg/dL). Prolonged length of stay (LOS) was defined as LOS above the 75th percentile. Associations between occult malnutrition, MNA categories, and prolonged LOS were examined using chi-square tests and multivariable logistic regression models adjusted for age ≥ 85 years, sex, primary reason for hospital admission and comorbidity burden.

Among 172 acutely hospitalized older adults (mean age 86.7 ± 6.0 years), hypoalbuminemia, anemia, and elevated CRP were observed in 42.4%, 46.5%, and 72.1% of patients, respectively. Occult malnutrition was identified in 54.7% of the cohort. Prolonged length of stay (LOS > 75th percentile) occurred in 50.0% of patients. Compared with patients without occult malnutrition, those with occult malnutrition were older, had significantly longer hospital stays, and a higher prevalence of prolonged LOS (59.6% vs. 38.5%, p = 0.006). The prevalence of occult malnutrition increased across worsening MNA categories (p = 0.022) and was present in 40.7% of patients with a normal MNA score. Occult malnutrition was independently associated with prolonged LOS in multivariable models adjusting for age, sex, admission reason, comorbidity burden, and MNA (adjusted OR range 1.97-2.14, all p < 0.05), whereas MNA itself was not independently associated with prolonged hospitalization.

A stringent biological definition of occult malnutrition identifies a large subgroup of hospitalized older adults at increased risk of prolonged hospitalization, including patients considered nutritionally normal by standard screening. These findings underline the limitations of screening-based assessment alone and support the use of simple biological markers to refine risk stratification in acute geriatric care.