Brain abscess, a serious intracranial infection, manifests as a pus collection within the brain tissue (1). Its complex pathogenesis involves a variety of infectious agents, such as bacteria (2), fungi (3), and parasites (4). Risk factors for the formation of a brain abscess include skull injuries, peripheral infections, a compromised immune system, malnutrition, and factors associated with advanced age. Brain abscesses can lead to severe consequences such as increased intracranial pressure, consciousness disturbances, brain herniation, abscess rupture causing meningitis or ventriculitis, focal neurological deficits, and seizures (5). The mortality rate for brain abscesses is around 10%, with 45% of affected patients experiencing neurological deficits post-treatment (4, 6, 7). In older patients, this mortality rate increases, with studies indicating a range of 20 to 40% (4, 7). The Glasgow outcome scale (GOS) is a scale used to systematically evaluate post-brain injury recovery, categorizing outcomes into five levels: death, vegetative state, severe disability, moderate disability, and good recovery (8). The GOS has been employed widely as a metric to assess the effectiveness of brain injury treatment and rehabilitation strategies (9, 10).

Nutritional status significantly influences the progression of brain abscesses and the efficacy of treatments (11). Inadequate nutrition weakens immune defenses, increasing infection risks (12). Furthermore, nutritional health is vital during treatment and recovery, with nutritional deficits potentially delaying wound healing, impeding neurological recovery, and prolonging the recovery process (13). Such deficiencies can negatively impact patient lifespan, and quality of life, and impose significant economic costs (14). The incidence of malnutrition and risk of nutritional deficits in elderly populations within hospital and nursing facility settings is nearly 50%. This condition is detrimental, with a profound link to clinical outcomes, and it significantly amplifies the risk of geriatric syndromes including dependency in activities of daily living, myasthenia gravis, and frailty (15). Given the heightened risk of malnutrition among the older due to aging, conducting a simple and objective assessment of malnutrition risk is imperative to develop effective nutritional interventions. The geriatric nutritional risk index (GNRI) serves as an objective screen tool to evaluate the nutritional status of older individuals and its association with health risks (16). The GNRI has emerged as a powerful prognostic indicator for the older, particularly regarding long-term postoperative outcomes (17–19). Numerous studies have demonstrated the utility of the GNRI in predicting outcomes among a wide range of clinical conditions in the older, including chronic kidney disease (20), heart failure (21), chronic obstructive pulmonary disease (22), and sepsis (23). Additionally, GNRIs have relevant applications in brain-related injuries. Su et al.’s study revealed that the GNRI is a prognostic factor for death in older patients with moderate to severe traumatic brain injuries (24). Furthermore, evidence from another study highlighted that a lower GNRI is an independent predictor of brain infarction and hemorrhage in patients on maintenance hemodialysis (25). Similarly, the study by Dai et al. demonstrated that GNRI was related to the risk of stroke-associated pneumonia (26).

To our knowledge, no study has examined the nutritional status of brain abscess patients and its correlation with clinical outcomes. Therefore, this study employed the GNRI to assess the risk of malnutrition among older brain abscess patients, exploring the relationship between nutritional status and clinical features. Additionally, we employed the GOS to evaluate recovery post-discharge in these patients, further exploring GNRI’s predictive value for GOS scores in older brain abscess patients’ post-discharge.

This study’s final analysis included a cohort of 100 older patients diagnosed with brain abscess. Table 1 revealed the median age to be 68 years (IQR 64.5–72), with females constituting 61% (61/100) of the sample. In this cohort, 11% (11/100) were underweight, and 30% (30/100) were overweight. The proportion of alcohol consumption and smoking was noted in 19% (19/100) and 18% (18/100) of the patients, respectively. Comorbidities were prevalent in older brain abscess patients, with the median number of comorbidities being 2 (IQR 0–3). The most common comorbidity was hypertension (36%, n = 36), followed by diabetes (31%, n = 31). GNRI assessments conducted within 48 h of admission indicated malnutrition risks in 48% of patients, with 4% facing major malnutrition risk, 23% moderate risk, and 21% low risk. The median hospital stay duration was 15 days (IQR 10–22), and the median GOS score at 6 months post-discharge was 5 (IQR 3–5), reflecting generally favorable outcomes.

As shown in Table 2, individuals at risk for malnutrition had significantly lower BMI compared to those not at risk (p < 0.001). This group also had a higher median comorbidity count of 3 (IQR 1–4) (p < 0.001), suggesting a higher burden of comorbid conditions. Furthermore, aCCI scores were significantly higher in the malnutrition risk group (p < 0.001). Admission CRP levels were also higher in the malnutrition risk group than in the non-risk group (p = 0.017), indicating more severe inflammation. Treatment strategies varied, with a larger fraction of the malnutrition risk group receiving conservative medical treatment (66.7%) compared to the non-risk group (38.5%) (p = 0.003). Additionally, the malnutrition risk group had lower median GOS scores of 3 (IQR 3–4) (p < 0.001), indicating a worse prognosis.

Table 3 demonstrated the relationships between GNRI scores and various clinical parameters. Specifically, CRP levels (Spearman’s ρ = −0.291, p = 0.006), the total number of comorbidities (Spearman’s ρ = −0.284, p = 0.004), and aCCI scores (Spearman’s ρ = −0.310, p = 0.002) are inversely correlated with GNRI scores. In contrast, GOS scores show a strong positive correlation with GNRI scores (Spearman’s ρ = 0.624, p < 0.001), indicating that higher nutritional status is associated with better neurological outcomes. Figure 2 delineates the distribution of GOS scores across varying malnutrition risk categories, with the precise value distribution elaborated in Supplementary Table S1 (p < 0.001). Furthermore, by assigning numerical values to surgical methods—1 for conservative therapeutic, 2 for aspiration, and 3 for excision—a positive correlation is observed between these values and GNRI scores (Spearman’s ρ = 0.340, p < 0.001). This suggests a preference for conservative treatment in patients with poorer nutritional status, consistent with the trends shown in Table 2.

In the univariate logistic regression analyses, the association of each predictor variable with the GOS score was assessed. The results revealed no significant correlation for age or gender with the GOS score. BMI and GNRI score were significantly negatively correlated with the GOS score, whereas CRP, aCCI score, and number of comorbidities showed a positive correlation with the GOS score. In the subsequent multivariable logistic regression analysis, which incorporated variables with a p-value of less than 0.2 from the univariate analysis, GNRI was found to have a significant negative correlation with GOS score (Table 4). This highlights GNRI’s potential as a predictive factor for outcomes. Additionally, Figure 3 showed the ROC curve for GNRI in predicting poor recovery. The analysis yielded an Area Under the Curve (AUC) of 0.903, with the 95% Confidence Interval (CI) extending from 0.832 to 0.975. At the optimal threshold of 97.50, with a sensitivity of 90.57% and a specificity of 87.23% in predicting recovery outcomes.

This study represents the first study into the association between malnutrition risk, as determined by the GNRI, and clinical outcomes in older patients with brain abscess. Findings from this prospective cohort study revealed that nearly half of the older brain abscess patients exhibited malnutritional risk, which is related to their treatment modality as well. Concurrently, the GNRI displayed associations with both the quantum of comorbidities and the aCCI score, underscoring the intricate interplay between nutritional status and the aggregate health burden in this demographic. Notably, older brain abscess patients presenting with lower GNRI scores were observed to have diminished GOS scores, indicating that GNRI has a predictive impact on their clinical outcomes.

Malnutrition, often underreported and underdiagnosed, is widespread among older hospitalized patients, contributing to adverse clinical outcomes such as prolonged hospital stays and elevated mortality rates (29). The GNRI provides an efficient, objective, and age-specific approach to nutritional screening in the older (16). It assesses the nutritional risks of the older in a timely and accurate manner by utilizing current weight metrics and serum albumin levels, thereby minimizing recall bias associated with past weight changes (16). In this study, the GNRI was employed to assess the malnutrition risk in older patients with brain abscesses, revealing a significant prevalence of 48%. Similarly, Bao et al.’s study revealed that among older patients experiencing early neurological deterioration following acute ischemic stroke, 48.3% were at risk of malnutrition according to GNRI (30). In another study, the GNRI assessment revealed a malnutrition risk of approximately 42.5% (97/228) among older patients with mild traumatic brain injury (31). These results above suggest that brain injury in older patients is often accompanied by malnutrition. This high incidence of malnutrition in the older adults may be attributed to various factors. With advancing age, oral issues such as missing teeth impair chewing ability, impacting food intake and digestion (32). Moreover, older individuals frequently contend with chronic diseases like diabetes and heart disease, potentially increasing metabolic demands and subsequently heightening the risk of malnutrition (33). This study’s findings revealed a significant negative correlation between GNRI and the level of comorbidity, further substantiated that the heightened burden of chronic diseases contributes to the increased risk of malnutrition.

As an infectious disease affecting the nervous system, brain abscesses induce inflammation that escalates the body’s metabolic demands, thereby heightening nutritional requirements (1, 34). This, combined with the adverse effects of infection and pharmacological treatments on appetite, can precipitate a further decline in the nutritional status of patients with brain abscesses (34). In the correlation analysis conducted in this study, the GNRI and CRp values upon admission in older patients with brain abscesses were found to be significantly negatively correlated (p = 0.006), thereby further indicating the relation between the level of inflammation and the nutritional risk. Furthermore, we observed that patients at nutritional risk underwent more conservative treatment during hospitalization compared to their counterparts without nutritional risk (38.5% vs. 66.7%). This finding implies that the nutritional status of older patients with brain abscess may influence their treatment approach.

In clinical practice, the typical focus on infection control and acute neurological symptom management in brain abscess cases often overshadows the scrutiny of patients’ nutritional status. The findings of this study indicated that older brain abscess patients at higher malnutrition risk exhibit poorer clinical prognoses (p < 0.001). A positive correlation emerged between GNRI scores and GOS scores (p < 0.001), indicating a nutritional status may be significantly associated with recovery and long-term outcomes in brain abscess patients. Several studies also have demonstrated a correlation between elevated malnutrition risks and adverse clinical outcomes in geriatric patients (31, 35). It can be seen that in the process of diagnosis and treatment of geriatric diseases, the assessment of nutritional status cannot be ignored. However, there is no significant correlation was observed between smoking, alcohol consumption, and either the nutritional status or the GOS in elderly patients with brain abscess in this study. This lack of association is likely due to the standardized, individualized treatment these patients received, which effectively minimized the impact of lifestyle factors on their outcomes (36). The findings emphasize the importance of tailored clinical management in mitigating the potential negative effects of smoking and alcohol use in this patient population.

GNRI has been employed as an independent predictive factor for morbidity and mortality in older hospitalized patients with cancer (37). Research on older colorectal cancer patients revealed that the preoperative GNRI served as an independent prognostic factor for those who underwent curative colorectal resection (38). In another study, the GNRI has been identified as an independent predictor of prognosis and postoperative complications after radical nephroureterectomy for upper urinary tract urothelial carcinoma (39). In addition to its extensive application in forecasting postoperative complications and the long-term prognosis of tumors, the GNRI was also employed in other diseases for its prognostic significance for recuperation and clinical outcomes. A study focused on older patients with mild traumatic brain injury revealed that a higher GNRI was associated with a decreased risk of incomplete recovery at the 6-month mark. Furthermore, the ROC analysis established a GNRI threshold of 97.85 (31). And GNRI was considered a promising tool for predicting mortality outcomes in older patients with moderate to severe traumatic brain injuries (24). These findings indicated that GNRI may have applicability in diseases related to brain injury. In our multivariate regression analysis, we found that lower GNRI values were positively associated with poorer prognosis (i.e., lower GOS score). Moreover, the results of the ROC analysis, which yielded an AUC of 0.903, underscore the significant potential of GNRI in predicting the long-term outcomes for older patients with brain abscess.

Our study offered several strengths. Firstly, as a prospective cohort study, the high standardization of our data collection protocols ensures data quality, while simultaneously reducing selection and recall biases. Secondly, this is the inaugural investigation into the prevalence of nutritional risk among older patients with brain abscesses, providing a novel insight into the clinical implications of GNRI scores. Furthermore, our use of logistic regression analysis has elucidated the relationship between GNRI and the prognostic score for geriatric brain abscesses (GOS), affirming GNRI’s utility in predicting outcomes for older hospitalized patients with brain abscesses. Meanwhile, our study still has certain limitations that should be considered. The study was conducted at a single center, which may limit the generalizability of the findings to other healthcare settings or diverse patient populations. The potential for selection bias and the lack of variability in patient demographics could affect the broader applicability of our results. Although the study utilized a standard nutritional assessment, it did not include specific evaluations for macro or micronutrient deficiencies. This omission may have restricted our understanding of the detailed nutritional profiles of elderly patients with brain abscesses and their impact on treatment efficacy and recovery outcomes. Additionally, reliance on a single prognostic measure, the GOS, may not fully capture the nuanced aspects of patient recovery, suggesting a need for more diverse and sensitive outcome assessment tools in future studies. Therefore, future research should be conducted across multiple centers, incorporate larger patient samples, and integrate additional nutritional assessment methods, such as Dual-energy X-ray Absorptiometry (DXA) or Bioelectrical Impedance Analysis (BIA). To deepen our understanding of the nutritional status of older patients with brain abscess and further explore the impact of nutritional status on treatment and clinical outcomes.

This study on the nutritional status of older patients with brain abscesses revealed that nearly half are at risk of malnutrition according to the GNRI. The GNRI is correlated with the number of comorbidities, aCCI scores, and treatment modalities, underscoring the intricate relationship between nutritional status and the overall health burden in this demographic. Moreover, the study observed that lower GNRI scores in these patients were associated with decreased GOS scores, and found that GNRI is a prognostic indicator of clinical outcomes. Clinically, heightened attention is warranted for patients with GNRI scores below the critical threshold of 97.5, and prompt nutritional interventions should be administered. Consequently, we advocate regular nutritional evaluations for all older patients with brain abscesses, ensuring early intervention with nutritional therapy to preserve their nutritional health and mitigate the risk of adverse outcomes.

The original contributions presented in the study are included in the article/Supplementary material, further inquiries can be directed to the corresponding authors.

The studies involving humans were approved by Ethics Committee of Huashan Hospital affiliated with Fudan University School of Medicine. The studies were conducted in accordance with the local legislation and institutional requirements. The participants provided their written informed consent to participate in this study.

XP: Conceptualization, Data curation, Formal analysis, Methodology, Writing – original draft. YZ: Data curation, Formal analysis, Writing – original draft. DJ: Data curation, Methodology, Writing – review & editing. MZ: Data curation, Methodology, Writing – review & editing. JF: Data curation, Writing – review & editing. YN: Supervision, Validation, Writing – review & editing. MT: Supervision, Visualization, Writing – review & editing. SH: Conceptualization, Supervision, Validation, Visualization, Writing – original draft, Writing – review & editing.