Low Geriatric Nutritional Risk Index Increases Postoperative Delirium Risk

Nutritional Vulnerability and Acute Postoperative Cognitive Decline

Postoperative delirium remains a frequent and costly complication in the geriatric surgical population, often leading to increased mortality, prolonged hospitalization, and a loss of functional independence [1, 2]. While several risk factors for this acute neurocognitive disorder are nonmodifiable, clinical focus has increasingly shifted toward identifying and addressing physiological vulnerabilities before the patient enters the operating room [3]. Malnutrition is a particularly significant concern, as it has been linked to a nearly threefold increase in delirium risk among patients undergoing surgery for hip fractures [4]. Current clinical guidelines emphasize the importance of multicomponent preventive strategies, yet the utility of specific, objective nutritional screening tools in predicting these adverse outcomes remains a subject of active investigation [2]. A new meta-analysis now offers fresh insights into the predictive value of a standardized nutritional index for identifying patients at risk for this postoperative complication.

Quantifying Risk Across 12,000 Surgical Patients

The researchers conducted this meta-analysis to clarify the association between the geriatric nutritional risk index and the risk of postoperative delirium. The geriatric nutritional risk index is a simple indicator of nutritional status calculated using a patient's serum albumin levels and body weight, providing a more objective measure than subjective dietary recalls. To gather relevant data, the authors performed a comprehensive search of PubMed, Embase, and Web of Science, specifically looking for observational studies that evaluated the relationship between categorized geriatric nutritional risk index scores and the development of delirium following surgery. The final analysis incorporated twelve cohort studies involving a total of 12,332 surgical patients, providing a robust sample size to evaluate clinical outcomes. Using random-effects models, which is a statistical method that assumes the effects being estimated vary across studies due to differences in patient populations or surgical types, the researchers calculated pooled risk ratios and 95% confidence intervals. The findings demonstrated that a low geriatric nutritional risk index was associated with a significantly increased risk of postoperative delirium, with a pooled risk ratio of 1.62 (95% CI: 1.34 to 1.96). This indicates that patients identified as nutritionally at risk by this metric are 62% more likely to experience delirium during their recovery, a finding that allows clinicians to flag high-risk individuals using existing laboratory data. The statistical reliability of these results was supported by a relatively low level of heterogeneity among the included studies, with an I-squared value of 27% for the primary outcome. This percentage, which measures the proportion of variation in effect estimates that is due to real differences between studies rather than chance, suggests that the geriatric nutritional risk index is a consistent tool for preoperative risk stratification. By integrating objective laboratory data like albumin, a marker of chronic protein status and systemic inflammation, with physical measurements of body weight, clinicians can more accurately identify vulnerable patients who may benefit from targeted nutritional interventions or enhanced delirium prevention protocols before undergoing surgery.

Age and Thresholds Influence Predictive Accuracy

The researchers performed subgroup analyses to determine how patient demographics and specific scoring thresholds affected the predictive power of the geriatric nutritional risk index. They found that the association between a low index score and postoperative delirium was significantly stronger in studies where the mean patient age was greater than 74 years compared to those with a mean age of 74 years or younger (p for subgroup difference = 0.02). This suggests that the oldest surgical patients may be particularly susceptible to the neurocognitive effects of poor nutritional status, perhaps due to reduced physiological reserve. Furthermore, the specific threshold used to define nutritional risk influenced the results. Studies utilizing geriatric nutritional risk index cutoffs of less than 98 demonstrated a stronger association with delirium than those using cutoffs of 98 or higher (p = 0.04). The strength of the correlation also varied based on the statistical methods employed across the included studies. The association between nutritional risk and delirium was weaker in studies that utilized multivariate analyses, which are statistical models that adjust for multiple confounding variables simultaneously such as comorbidities and surgical duration, compared to those using univariate analyses (p = 0.01). Despite this variation, the overall trend remained significant across different study designs. To further investigate the sources of heterogeneity, the authors conducted a meta-regression, a technique used to explore how study-level characteristics relate to the size of the effect. This meta-regression indicated that the specific geriatric nutritional risk index cutoff values significantly influenced the pooled effect (p = 0.04). These findings highlight the importance of selecting appropriate clinical thresholds when using nutritional indices to screen for postoperative complications in surgical settings, as a cutoff of 98 may serve as a more sensitive trigger for clinical intervention.

Clinical Implications for Preoperative Screening

The statistical integrity of these findings suggests that the geriatric nutritional risk index serves as a reliable tool for identifying patients at risk for postoperative delirium. Although the funnel plot showed mild asymmetry, which can sometimes suggest a bias toward publishing positive results, the Egger’s test for publication bias was not significant (p = 0.11). To further validate the data, the researchers performed a trim-and-fill analysis, a statistical method used to estimate the effect of potentially missing studies on the overall results by mathematically imputing "missing" data points to achieve symmetry. This trim-and-fill analysis produced a similar pooled estimate (RR = 1.54, 95% CI: 1.26 to 1.87), confirming that the 54 percent to 62 percent increase in delirium risk remains robust even after accounting for potential publication bias. For transparency and methodological rigor, the study protocol was registered prospectively in the PROSPERO database (registration number: CRD420261335609). For the practicing clinician, these results underscore that malnutrition is an important contributor to postoperative delirium, a complication that often leads to poor surgical outcomes and long-term cognitive decline. Because the geriatric nutritional risk index relies solely on serum albumin and body weight, it provides an objective and efficient method for preoperative screening that can be easily integrated into electronic health records. Identifying high-risk patients through this index allows for targeted preoperative nutritional optimization, potentially mitigating the neurocognitive decline associated with surgery. By integrating these two common clinical markers into standard preoperative assessments, surgical teams can better stratify risk and implement preventive strategies for the 12,332 patients represented in this meta-analysis and the broader geriatric surgical population.

References

1. Tjeertes EK, Fessem JMKV, Mattace‐Raso F, Hoofwijk AGM, Stolker RJ, Hoeks SE. Influence of Frailty on Outcome in Older Patients Undergoing Non-Cardiac Surgery - A Systematic Review and Meta-Analysis. Aging and Disease. 2020. doi:10.14336/ad.2019.1024

2. Aldecoa C, Bettelli G, Bilotta F, et al. Update of the European Society of Anaesthesiology and Intensive Care Medicine evidence-based and consensus-based guideline on postoperative delirium in adult patients. European Journal of Anaesthesiology. 2023. doi:10.1097/eja.0000000000001876

3. Adults TAGSEPOPDIO. American Geriatrics Society Abstracted Clinical Practice Guideline for Postoperative Delirium in Older Adults. Journal of the American Geriatrics Society. 2014. doi:10.1111/jgs.13281

4. Chiavarini M, Ricciotti G, Genga A, et al. Malnutrition-Related Health Outcomes in Older Adults with Hip Fractures: A Systematic Review and Meta-Analysis. Nutrients. 2024. doi:10.3390/nu16071069