Relationship between serum neutrophil gelatinase-associated lipocalin levels and cognitive impairment, anxiety, and depressive symptoms in acute ischemic stroke

Abstract

BACKGROUND

Acute ischemic stroke (AIS) is a significant global health issue with increasing incidence owing to aging populations and rising cardiovascular risk factors. In addition to physical impairments, AIS frequently leads to neuropsychiatric complications, such as cognitive impairment, anxiety, and depressive symptoms, which adversely affect patients’ quality of life and rehabilitation. Neutrophil gelatinase-associated lipocalin (NGAL) has emerged as a potential biomarker for various conditions, including AIS. This study investigated the association between serum NGAL levels at admission and neuropsychiatric complications in patients with AIS.

AIM

To investigate the relationship between serum NGAL levels at admission and neuropsychiatric complications in patients with AIS.

METHODS

Between January 2022 and December 2023, 150 patients with AIS were enrolled. Serum NGAL levels were measured at admission using an enzyme-linked immunosorbent assay. Cognitive function was assessed using the Mini-Mental State Examination, while anxiety and depressive symptoms were evaluated using the Hospital Anxiety and Depression Scale at discharge. The relationship between serum NGAL levels and cognitive impairment, anxiety, and depressive symptoms was analyzed using multivariate logistic regression, adjusted for potential confounders of age, sex, body mass index, smoking status, hypertension, diabetes mellitus, dyslipidemia, previous stroke, and stroke severity.

RESULTS

The mean age of the participants was 65.4 ± 10.2 years, and 58% were males. Prevalence rates of cognitive impairment, anxiety, and depressive symptoms at discharge were 34.7%, 28.0%, and 32.0%, respectively. Serum NGAL levels were significantly higher in patients with cognitive impairment (median: 5.6 ng/mL vs 3.2 ng/mL, P < 0.001), anxiety (median: 5.1 ng/mL vs 3.5 ng/mL, P = 0.002), and depressive symptoms (median: 5.4 ng/mL vs 3.3 ng/mL, P < 0.001), compared to those without these conditions. Multivariate logistic regression analysis showed that higher serum NGAL levels at admission were independently associated with cognitive impairment [odds ratio (OR) = 1.42, 95% confidence interval (CI): 1.18-1.71, P < 0.001], anxiety (OR = 1.28, 95%CI: 1.09-1.51, P = 0.003), and depressive symptoms (OR = 1.39, 95%CI: 1.16-1.67, P < 0.001) after adjusting for potential confounders.

CONCLUSION

Elevated serum NGAL levels were independently associated with cognitive impairment, anxiety, and depressive symptoms in patients with AIS; and may function as potential biomarkers for patients at risk.

Key Words: Neutrophil gelatinase-associated lipocalin; Neuropsychiatric complications; Biomarker; Acute ischemic stroke; Cognitive impairment; Anxiety; Depressive symptoms

Core Tip: This study reveals the relationship between serum neutrophil gelatinase-associated lipocalin (NGAL) levels at admission and neuropsychiatric complications, including cognitive impairment, anxiety, and depressive symptoms, in patients with acute ischemic stroke (AIS). The findings indicate that higher NGAL levels are significantly associated with these complications. NGAL can serve as a potential biomarker for early identification of patients with AIS at risk for neuropsychiatric issues, enabling timely interventions and improved outcomes. This study highlights NGAL’s multifaceted roles in AIS-related neuropsychiatric complications and its potential therapeutic implications.

INTRODUCTION

Acute ischemic stroke (AIS) is a major global health concern with an increasing incidence and prevalence due to an aging population and the rising burden of cardiovascular risk factors[1]. In addition to well-recognized physical impairments, AIS is frequently associated with neuropsychiatric complications, such as cognitive impairment, anxiety, and depressive symptoms[2]. These comorbidities adversely affect patients’ quality of life and hinder rehabilitation efforts and worsen overall prognosis[3]. Therefore, early identification of patients at risk for developing these complications is crucial for timely intervention and improved outcomes.

Neutrophil gelatinase-associated lipocalin (NGAL), a member of the lipocalin family, has emerged as a promising biomarker of various pathological conditions, including acute kidney injury, cardiovascular disease, and neurological disorders[4]. Recent studies have suggested that NGAL plays a role in the pathophysiology of ischemic stroke, with elevated levels observed during the acute phase of AIS[5,6]. To better understand the potential mechanisms underlying the relationship between NGAL and neuropsychiatric complications in AIS, it is essential to consider the multifaceted roles of NGAL in neuroinflammation, blood-brain barrier disruption, oxidative stress, and neurotransmitter signaling[7-10]. NGAL has been shown to be upregulated in activated microglia and astrocytes, contributing to the release of pro-inflammatory cytokines and chemokines, which may lead to neuronal damage and dysfunction[11,12]. Moreover, NGAL may be involved in blood-brain barrier disruption and oxidative stress, both of which have been implicated in the pathogenesis of neuropsychiatric complications after AIS[13,14]. Finally, NGAL regulates synaptic plasticity and neurotransmitter signaling, which are crucial for cognitive function and emotional processing[15,16].

However, the relationship between serum NGAL levels and neuropsychiatric complications following AIS remains largely unexplored. This study aimed to investigate the association between serum NGAL levels at admission with cognitive impairment, anxiety, and depressive symptoms in patients with AIS. We hypothesized that higher serum NGAL levels would be independently associated with an increased risk of developing these neuropsychiatric comorbidities after adjusting for potential confounders.

MATERIALS AND METHODS

Study design and participants

This prospective observational study was conducted from January 2022 to December 2023 in the Department of Neurology at the First Hospital of Lanzhou University in Gansu Province, China. The study protocol was approved by the Institutional Review Board, and written informed consent was obtained from all participants or their legal representatives. In total, 150 consecutive patients diagnosed with AIS were enrolled in this study. A diagnosis of AIS was confirmed using neuroimaging (computed tomography or magnetic resonance imaging) and a clinical assessment by an experienced neurologist. Patients were excluded if they had a history of a pre-existing cognitive impairment, psychiatric disorder, severe head trauma, or other neurological disease that may have affected their cognitive function or mood.

To ensure a comprehensive assessment of potential confounders, detailed demographic and clinical data, including age, sex, body mass index (BMI), smoking status, medical history (hypertension, diabetes mellitus, dyslipidemia, and previous stroke), and stroke severity were assessed using the National Institutes of Health Stroke Scale (NIHSS) score at admission, collected from medical records. Serum NGAL measurement blood samples were collected within 24 hours of admission, and serum NGAL levels were measured using a commercially available enzyme-linked immunosorbent assay kit (R&D Systems, Minneapolis, MN, United States) according to the manufacturer’s instructions. The assay had a detection range of 0.156-10 ng/mL, with intra- and inter-assay coefficients of variation of < 10%. All the samples were run in duplicate, and the mean values were used for the analysis.

Cognitive function assessment

Cognitive function was performed using the Mini-Mental State Examination (MMSE)[17] at discharge (approximately 7-10 days after admission). The MMSE is a widely used screening tool for cognitive impairment, with scores between 0-30. The MMSE assesses various cognitive domains, including orientation, registration, attention and calculation, recall, language, and visuospatial skills. Cognitive impairment was defined as an MMSE score of ≤ 24 points[18], which has been shown to have high sensitivity and specificity for detecting cognitive impairment in patients with stroke[19].

Anxiety and depressive symptoms assessment

Anxiety and depressive symptoms were evaluated using the Hospital Anxiety and Depression Scale (HADS)[20] at discharge. The HADS is a 14-item self-report questionnaire with two subscales (anxiety and depression), each containing seven items scored on a four-point Likert scale. The HADS has been validated for use in patients with stroke and has shown good psychometric properties[21]. Scores of ≥ 8 on either subscale are considered indicative of clinically significant anxiety or depressive symptoms[22].

Statistical analysis

Continuous variables are expressed as mean ± SD or median (interquartile range), depending on their distribution, while categorical variables are expressed as frequencies and percentages. Normality was assessed using the Shapiro-Wilk test. Comparisons between groups were performed using the Student’s t-test or Mann-Whitney U test for continuous variables, and the χ² test or Fisher’s exact test for categorical variables, as appropriate.

The relationships between serum NGAL levels and cognitive impairment, anxiety, and depressive symptoms were analyzed using multivariate logistic regression adjusted for age, sex, BMI, smoking status, hypertension, diabetes mellitus, dyslipidemia, previous stroke, and NIHSS score at admission. These potential confounders were selected based on their known associations with neuropsychiatric complications in patients with AIS. The results were expressed as odds ratios (ORs) with 95% confidence intervals (CI).

The relationships between serum NGAL levels and cognitive impairment, anxiety, and depressive symptoms were analyzed using multivariate logistic regression adjusted for age, sex, BMI, smoking status, hypertension, diabetes mellitus, dyslipidemia, previous stroke, and NIHSS score at admission. These potential confounders were selected based on their known associations with neuropsychiatric complications in patients with AIS[23,24]. Continuous variables were included as linear terms, while categorical variables were included as dummy variables. The results were expressed as ORs with 95%CI.

A receiver operating characteristic (ROC) curve analysis was performed to further explore the discriminative ability of serum NGAL levels to predict cognitive impairment, anxiety, and depressive symptoms; and the optimal cut-off value for serum NGAL levels was determined using the Youden index (sensitivity + specificity - 1). All statistical analyses were performed using SPSS version 25.0 (IBM Corp., Armonk, NY, United States). Statistical significance was set at a two-tailed P value < 0.05.

RESULTS

Baseline characteristics

The study comprised 150 patients with AIS (mean age: 65.4 ± 10.2 years; 58% male). The median NIHSS score at admission was 6 (interquartile range: 3-10), indicating moderate stroke severity. The prevalence rates of cognitive impairment, anxiety, and depressive symptoms at discharge were 34.7%, 28.0%, and 32.0%, respectively. Table 1 provides the baseline characteristics of the study population, stratified by the presence or absence of cognitive impairment, anxiety, and depressive symptoms. Patients with cognitive impairment were significantly older (P = 0.010) and had higher NIHSS scores upon admission (P = 0.001) than those without cognitive impairment. There were no significant differences in age, sex, BMI, smoking status, or comorbidities between patients with and without anxiety or depressive symptoms.

Table 1 Baseline characteristics of the study population stratified by the presence or absence of cognitive impairment, anxiety, and depressive symptoms.

Characteristic	Cognitive impairment		P value	Anxiety		P value	Depressive symptoms		P value
	Yes (n = 52)	No (n = 98)		Yes (n = 42)	No (n = 108)		Yes (n = 48)	No (n = 102)
Age, year, mean ± SD	68.3 ± 9.5	63.8 ± 10.3	0.010	66.9 ± 9.8	64.8 ± 10.3	0.261	67.5 ± 9.6	64.4 ± 10.3	0.083
Male, n (%)	28 (53.8)	59 (60.2)	0.448	22 (52.4)	65 (60.2)	0.379	25 (52.1)	62 (60.8)	0.312
BMI, kg/m2, mean ± SD	24.8 ± 3.2	24.3 ± 3.1	0.356	24.5 ± 3.3	24.5 ± 3.1	0.980	24.6 ± 3.2	24.4 ± 3.1	0.720
Smoking, n (%)	18 (34.6)	30 (30.6)	0.614	15 (35.7)	33 (30.6)	0.540	17 (35.4)	31 (30.4)	0.534
Hypertension, n (%)	37 (71.2)	61 (62.2)	0.273	29 (69.0)	69 (63.9)	0.548	33 (68.8)	65 (63.7)	0.544
Diabetes, n (%)	19 (36.5)	28 (28.6)	0.311	15 (35.7)	32 (29.6)	0.472	18 (37.5)	29 (28.4)	0.262
Dyslipidemia, n (%)	28 (53.8)	46 (46.9)	0.415	22 (52.4)	52 (48.1)	0.639	25 (52.1)	49 (48.0)	0.637
Previous stroke, n (%)	10 (19.2)	14 (14.3)	0.417	8 (19.0)	16 (14.8)	0.522	9 (18.8)	15 (14.7)	0.523
NIHSS score at admission, median (interquartile range)	8 (5-12)	5 (3-9)	0.001	7 (4-11)	6 (3-9)	0.118	8 (4-12)	5 (3-9)	0.007

BMI: Body mass index; NIHSS: National Institutes of Health Stroke Scale.

Serum NGAL levels and neuropsychiatric comorbidities

Patients with cognitive impairment had significantly higher serum NGAL levels at admission compared to those without cognitive impairment (median: 5.6 ng/mL vs 3.2 ng/mL, P < 0.001). Similarly, serum NGAL levels were higher in patients with anxiety (median: 5.1 ng/mL vs 3.5 ng/mL, P = 0.002) and depressive symptoms (median: 5.4 ng/mL vs 3.3 ng/mL, P < 0.001) compared to those without these conditions (Table 2).

Table 2 Serum neutrophil gelatinase-associated lipocalin levels at admission in patients with and without cognitive impairment, anxiety, and depressive symptoms.

Neuropsychiatric complication	Serum NGAL levels (ng/mL)		P value
	Yes	No
Cognitive impairment, median (interquartile range)	5.6 (4.2-7.1)	3.2 (2.4-4.3)	< 0.001
Anxiety, median (interquartile range)	5.1 (3.8-6.6)	3.5 (2.6-4.7)	0.002
Depressive symptoms, median (interquartile range)	5.4 (4.0-6.9)	3.3 (2.5-4.5)	< 0.001

NGAL: Neutrophil gelatinase-associated lipocalin.

Multivariate analysis and ROC curve analysis

Multivariate logistic regression analysis revealed that higher serum NGAL levels at admission were independently associated with an increased risk of cognitive impairment (OR = 1.42, 95%CI: 1.18-1.71, P < 0.001), anxiety (OR = 1.28, 95%CI: 1.09-1.51, P = 0.003), and depressive symptoms (OR = 1.39, 95%CI: 1.16-1.67, P < 0.001) after adjusting for age, gender, BMI, smoking status, hypertension, diabetes mellitus, dyslipidemia, previous stroke, and NIHSS score at admission (Table 3).

Table 3 Multivariate logistic regression analysis of the association between serum neutrophil gelatinase-associated lipocalin levels and neuropsychiatric comorbidities.

Outcome	Odds ratio (95%CI)	P value
Cognitive impairment	1.42 (1.18-1.71)	< 0.001
Anxiety	1.28 (1.09-1.51)	0.003
Depressive symptoms	1.39 (1.16-1.67)	< 0.001

Adjusted for age, sex, body mass index, smoking status, hypertension, diabetes mellitus, dyslipidemia, previous stroke, and National Institutes of Health Stroke Scale score at admission. CI: Confidence interval.

Analysis of subject operating characteristic curve

Receiver operating characteristic curve analysis showed that serum NGAL levels had good discriminative ability for predicting cognitive impairment [area under the ROC curve (AUC) = 0.78, 95%CI: 0.71-0.85], anxiety (AUC = 0.67, 95%CI: 0.58-0.76), and depressive symptoms (AUC = 0.71, 95%CI: 0.63-0.79) (Table 4).

Table 4 Discriminative ability of serum neutrophil gelatinase-associated lipocalin levels for predicting cognitive impairment, anxiety, and depressive symptoms using receiver operating characteristic curve analysis.

Neuropsychiatric complication	AUC (95%CI)	Optimal cut-off value (ng/mL)	Sensitivity (%)	Specificity (%)
Cognitive impairment	0.78 (0.71-0.85)	4.2	75.0	70.4
Anxiety	0.67 (0.58-0.76)	4.0	66.7	63.0
Depressive symptoms	0.71 (0.63-0.79)	4.1	70.8	65.7

AUC: Area under the receiver operating characteristic curve; CI: Confidence interval.

DISCUSSION

This prospective observational study demonstrated a significant association between elevated serum NGAL levels at admission and cognitive impairment, anxiety, and depressive symptoms in patients with AIS. These findings suggest that the serum NGAL level may serve as a potential biomarker for the early identification of patients at risk of developing neuropsychiatric complications following AIS. The mechanisms underlying the relationship between NGAL and neuropsychiatric comorbidities in AIS are likely to be multifactorial and involve complex interactions among neuroinflammation, blood-brain barrier disruption, oxidative stress, and neurotransmitter signaling[7-10]. NGAL has been shown to be upregulated in activated microglia and astrocytes, contributing to the release of pro-inflammatory cytokines and chemokines, which may lead to neuronal damage and dysfunction[11,12]. Moreover, NGAL may be involved in blood-brain barrier disruption and oxidative stress, both of which have been implicated in the pathogenesis of neuropsychiatric complications after AIS[13,14]. Finally, NGAL regulates synaptic plasticity and neurotransmitter signaling, which are crucial for cognitive function and emotional processing[15,16].

The early identification of patients at risk for developing cognitive impairment, anxiety, and depressive symptoms following AIS is crucial for timely intervention and improved outcomes. Our findings suggest that serum NGAL levels at admission may help stratify patients according to their risk of developing neuropsychiatric complications. The ROC curve analysis revealed that serum NGAL levels had a good discriminative ability for predicting cognitive impairment, anxiety, and depressive symptoms, with optimal cut-off values ranging from 4.0-4.2 ng/mL. These results highlight the potential utility of serum NGAL as a biomarker for risk stratification and targeted intervention in patients with AIS.

The implementation of targeted screening, monitoring, and therapeutic strategies based on serum NGAL levels may prevent or mitigate the effect of neuropsychiatric comorbidities on patients’ quality of life and overall prognosis. For example, patients with elevated serum NGAL levels can be closely monitored for the development of cognitive impairment and mood disorders, and early intervention with cognitive rehabilitation, psychological support, or pharmacotherapy may be initiated as needed. Future studies are required to explore the potential therapeutic implications of targeting NGAL and its associated pathways for the management of AIS-related neuropsychiatric complications. Our findings are consistent with several previous studies that have reported associations between elevated NGAL levels and neurological outcomes in patients with stroke. For example, Peng et al[25] reported that elevated levels of NGAL in ischemic brain tissue are associated with ischemic brain injury. Similarly, Zwirner et al[26] reported that the diagnostic accuracy of traumatic brain injury can be improved by biomarkers of central nervous system including NGAL.

Furthermore, our results align with the recent study by Liu et al[27], which investigated the relationship between serum lipocalin 2, also known as NGAL, and post-stroke depression (PSD) in patients with AIS. Their study of 358 patients with AIS observed that 25.7% were diagnosed with PSD at discharge. After adjusting for multiple potential confounding factors, they observed that the highest tertile of serum lipocalin 2 levels (≥ 140.12 ng/mL) was independently associated with the occurrence of PSD (OR = 2.639, 95%CI: 1.317-5.287, P = 0.006).

The strengths of this study include its prospective design, comprehensive assessment of cognitive function and mood symptoms using validated tools, adjustment for a wide range of potential confounders in the multivariate analysis, and use of the ROC curve analysis to evaluate the discriminative ability of serum NGAL levels. However, this study has several limitations. First, the single-center design and relatively small sample size may have limited the generalizability of our findings. Large multicenter studies are required to validate these results in diverse populations. Second, cognitive function and mood symptoms were assessed only at discharge, precluding the evaluation of long-term outcomes. Future studies should include longitudinal assessments to investigate the prognostic value of serum NGAL levels on long-term cognitive and neuropsychiatric outcomes. Third, the observational nature of this study did not allow for causal inferences. Experimental studies are needed to elucidate the mechanistic links between NGAL levels and neuropsychiatric complications in patients with AIS. Finally, we did not assess other potential biomarkers or neuroimaging parameters that may have contributed to the development of cognitive impairment or mood disorders following AIS. Future studies should employ a multimodal approach, integrating serum biomarkers, neuroimaging, and clinical assessments to improve risk stratification and personalized management of patients with AIS.

CONCLUSION

This study demonstrates that elevated serum NGAL levels at admission are independently associated with cognitive impairment, anxiety, and depressive symptoms in patients with AIS. These findings highlight the potential role of NGAL as a biomarker for the early identification of patients at risk of developing neuropsychiatric complications. Further studies are warranted to validate these results in larger multicenter cohorts, investigate the long-term prognostic value of serum NGAL levels, and explore the potential therapeutic implications of targeting NGAL in the management of AIS-related neuropsychiatric comorbidities. By improving our understanding of the complex interplay between NGAL, neuroinflammation, and neuropsychiatric complications in AIS, more effective strategies for prevention, early intervention, and personalized care may be developed, ultimately improving the quality of life and outcomes of stroke survivors.