Pre-admission Nutritional Risk as an Independent Predictor of 28-Day Mortality After Hip Fracture: A Retrospective Cohort Study.

backgroundHip fracture carries a substantial risk of early mortality in older adults. Malnutrition is common in this population and is closely correlated with age, frailty, and cognitive impairment, making its independent contribution to short-term mortality difficult to disentangle from these established prognostic factors. Whether nutritional risk on admission predicts 28-day mortality after accounting for age, sex, anesthetic risk grade, and cognitive status remains uncertain.

methodsWe conducted a retrospective cohort study of 709 consecutive patients admitted with hip fracture. Nutritional risk was assessed on admission using the Malnutrition Universal Screening Tool (MUST) and categorized as normal or any nutritional risk (at-risk and malnourished combined) for the primary analysis. The primary outcome was all-cause mortality within 28 days. Eighteen patients with an ungradable American Society of Anesthesiologists (ASA) grade were excluded, leaving 691 patients in the final analysis. Multivariable logistic regression estimated the association between nutritional risk and 28-day mortality, adjusting for age, sex, ASA grade, and admission cognitive status (Abbreviated Mental Test Score (AMTS)). Sensitivity analyses examined a three-category MUST classification; exploratory analyses examined post-admission delirium and mobilization status.

resultsOf 691 patients, 128 (18.5%) had nutritional risk on admission. Twenty-eight-day mortality was higher in this group than in patients with normal nutritional status (14.8% vs 5.2%; p < 0.001). Nutritional risk remained independently associated with mortality after adjustment (adjusted odds ratio (OR) 3.24, 95% confidence interval (CI) 1.65-6.35; p = 0.0006), with minimal change from the unadjusted estimate (OR 3.21, 95% CI 1.74-5.93), indicating the association is not substantially explained by age, sex, ASA grade, or cognition. Male sex (adjusted OR 3.31; p = 0.0003) and lower AMTS (adjusted OR 0.90 per point; p = 0.009) were independently predictive. In a sensitivity analysis using the three-category MUST classification, the "at-risk" group remained independently associated with mortality (adjusted OR 3.87, 95% CI 1.87-7.99), while the "malnourished" group did not reach statistical significance (adjusted OR 1.77, 95% CI 0.48-6.52), likely reflecting limited power in this smaller subgroup. Delirium severity and failure to mobilize postoperatively were both strongly associated with mortality in exploratory analyses (both p < 0.001) but were excluded from the primary model as post-admission factors.

conclusionAdmission nutritional risk, as identified by the MUST, was associated with 28-day mortality following hip fracture, independent of age, sex, ASA grade, and cognitive status, although residual confounding by unmeasured factors cannot be excluded. These findings support the value of early nutritional assessment as part of a broader, multidimensional approach to identifying patients at increased risk of early death.