Analysis of Immune Dysfunction and Predictors of Poor Prognosis in Patients with Alzheimer's Disease

[Abstract] Background: Alzheimer’s disease (AD) is a serious disease causing human dementia and social problems. The quality of life and prognosis of AD patients have attracted much attention. The role of chronic immune inflammation in the pathogenesis of AD is becoming more and more important. It is necessary to study the relationship among cognitive dysfunction, abnormal cellular immune function, neuroimaging results and poor prognostic factors in patients. Methods: A retrospective analysis of 62 hospitalized patients clinical diagnosed with AD who were admitted to our hospital from November 2015 to November 2020. Collect cognitive dysfunction performance characteristics, laboratory test data and neuroimaging data from medical records within 24 hours of admission, including MMSE score, drawing clock test (CTD), blood T lymphocyte subsets, and neutrophils and lymphocyte ratio (NLR), disturbance of consciousness, extrapyramidal symptoms, electroencephalogram (EEG) and head nucleus magnetic spectroscopy (MRS) and other data. Multivariate logistic regression analysis was used to determine independent prognostic factors. the modified Rankin scale (mRS) was used to determine whether the prognosis was good. The correlation between drug treatment and prognostic mRS score was tested by the rank sum test. Results: Univariate analysis showed that abnormal cellular immune function,


Introduction
Alzheimer's disease (AD) is a neurodegenerative disease with severe cognitive dysfunction.
The prominent clinical manifestations are memory loss, confusion of thinking and logic, and abnormal mental behavior. It accounts for about 40-60% of dementia patients ( Scheltens et al., 2016;Jacus et al., 2020). At present, it is also inclined to think that AD is a chronic inflammatory significance. Some AD patients may have a long life, but whether this longevity has social value is worth exploring. Longevity with obvious lack of quality of life and heavy burden on families may not be worth advocating. We need to make AD patients live a healthy life and return to society as much as possible (Reitz, 2015;Wang et al., 2020).
The role of chronic immune inflammation in the pathogenesis of AD is becoming more and more important. The ratio of neutrophil to lymphocyte (NLR) in blood is an important systemic inflammatory biomarker. NLR is calculated by absolute counting of neutrophils divided by absolute counts of lymphocytes. NLR has been reported to be increased in diabetes, hypertension, myocardial infarction. stroke and some tumor patients, which may be a new index to evaluate the prognosis of these patients (Kim et al., 2020;Sayed et al., 2020;Hamelin., 2018). The detection of T lymphocytes, B lymphocytes and natural killer cells in blood by flow cytometry can evaluate whether the immune function of AD patients is abnormal. Combined with the detection of relevant biochemical markers and EEG wave indexes by cranial MRS, it has great clinical significance for the early diagnosis and prognosis evaluation of AD patients. As far as we know, little research work has been carried out in this regard (Fani et al., 2021;Bregman et al., 2020). Therefore, this study focuses on the correlation between abnormal immune function and adverse prognostic factors in AD patients, and hope to find some valuable clues.

Case study
This retrospective case study was reviewed and approved by the Medical Ethics Committee The 68 patients in this retrospective study are all clinically diagnosed AD patients. The 68 AD patients who met the needs of this study were selected for follow-up. After the patients are discharged from the hospital, they will be followed up and followed up by family members or guardians by telephone every 3 months. The prognosis will be assessed after detailed inquiries, and semi-quantitative according to the classic scale.

Data collection
Collect the following medical history and clinical data: age of onset, gender, chief complaint, duration of disease, first symptoms, other symptoms, main positive signs, cranial MRI, cranial magnetic spectroscopy (MRS), electroencephalogram (EEG), blood routine, blood immunity Results of cell examination and drug treatment. The main metabolites detected by MRS include N-acetylaspartate (NAA), creatine (Cr), choline (Cho), inositol (MI), etc. NAA/Cr ratio and MI/Cr ratio were collected as key analysis indicators. Regarding EEG data, it is mainly to pay attention to the abnormal β wave and slow wave (θ wave and δ wave), especially the ratio of (θ+δ) to (α+β) in the whole brain [(θ+δ)/(α+β)]. We also pay attention to the ratio of neutrophils to lymphocytes (NLR) in the blood. The percentage values of T lymphocytes, B lymphocytes and natural killer cells (NK cells) detected by flow cytometry are also collected. As the value of Aβ protein and tau protein in the blood in the diagnosis of AD is controversial sometimes, this study was not collected. The decrease of Aβ42 protein in the cerebrospinal fluid (CSF) and the increase of phosphorylated tau protein do have certain value in the diagnosis of AD, but there are many lack of data in this group of cases, and they have not been collected. In addition, we collected MMSE score data and cognitive function screening scale scores for AD patients.

Prognosis assessment
The Modified Rankin Scale (mRS) was used to assess neurological function at admission, discharge, and follow-up. There are 6 grades of mRS score: 0 score is for full recovery; a score of 1 score is defined as having no apparent dysfunction or being able to perform daily life and work tasks despite symptoms; 2 score is mild disability, but basically able to complete daily life and work tasks independently; 3 score is moderate disability, unable to complete all previous activities, difficult to handle own affairs independently; 4 score is severely disabled and needs to be cared for by someone else; 5 score is severe disability who require intensive care by medical staff; 6 score is defined as death case. According to The mRS during the follow-up period, all patients were divided into two groups: Those with mRS score of 0-2 scores were defined as "good prognosis"; 3-6 scores was defined as "poor prognosis".

Statistical analysis
SPSS software was used for statistical analysis (version 17.0). The data collected are expressed as mean ± standard deviation or median (range). Count data is expressed as a ratio or percentage. Univariate correlation analysis was used to compare the differences between the two groups. Student t test or Mann Whitney test is used for measurement data, t test is used for variables with normal distribution, and Mann Whitney test is used for variables with non normal distribution. The counting data were compared by chi square test. Logistic regression analysis was used to determine the independent risk factors of poor prognosis. Differences in MRS scores between two groups were determined using Spearman rank correlation test. The best cut-off value of NAA/Cr as a prognostic index of AD was determined by the analysis of receptor working curve (ROC). P values less than 0.05 (bilateral) were considered statistically significant.

Basic information of clinical data:
Through the electronic medical records database of the inpatient department and medical record

Auxiliary inspection results:
The

The relevant situation of the treatment effect:
All patients were treated with medications, mainly medications that may improve cognitive

Prognosis and predictive factors
Univariate analysis showed that there were significant differences in five indexes in the corresponding auxiliary examination test values between the groups with good prognosis and poor prognosis, including Hallucination (P = 0.025), abnormal EEG (P = 0.003), the ratio of (θ+δ)/(α+β) by EEG (P=0.019), abnormality of hippocapus (P = 0.001), the proportion of T lymphocytes obtained by flow cytometry (P=0.008). We found that the proportion of T lymphocytes <55% can be used as the cut-off threshold for predicting the poor prognosis of AD. We also found that the ratio of (θ+δ)/(α+β) was usually greater than or equal to 1.8 in the poor prognosis group. In addition, patients with severe depressive symptoms, moderate or severe brain atrophy, severe abnormal electroencephalogram, and significantly reduced ratios of T lymphocytes or NK cells were associated with poor prognosis in AD patients ( Table 2).  The NLR ratio in blood, the severity of memory impairment and the time of drug treatment had no significant correlation with the prognosis of AD patients. The ROC analysis of NAA / Cr obtained by MRS can predict the adverse prognosis of AD patients, and the area under the curve is 0.825 (95% CI, 0.126-0.958; P ＜ 0.01). According to the ROC curve, the best intercept value is 1.52, the sensitivity is 85.6%, and the specificity is 89.3% (see Figure 2). Subsequently, Spearman correlation analysis or the Rank Sum test was performed. The correlation between the NAA/Cr ratio and mRS score after the treatment of donepezil in 28 patients was analyzed, and it was found that there was a positive correlation between the two group (r = 0.609, P < 0.05); The number of days of donepezil treatment to improve cognitive function was negatively correlated with mRS score (r= 0.578, P＜0.05).

Discussion
In this project, we retrospectively studied the subsequent prognosis of patients initially diagnosed with AD. We analyzed the clinical features, blood examination results, imaging data, EEG results and flow cytometry results. It also focused on the factors that are closely related to the poor prognosis. This study showed that the median T lymphocyte percentage in the poor prognosis group was significantly lower than that in the good prognosis group. resonance spectrum peaks in the MRS examination: NAA peak, Choline complex (Cho) peak, Cr peak, inositol peak, and glutamate peak. The decrease in NAA peak can be used as a sign of neuron loss or damage in the brain. The content of Cr in the gray matter of the brain is higher than that of the white matter, and it is a high energy phosphoric acid reserve substance for ATP/ADP conversion (Joe et al., 2019). This research found that the NAA/Cr ratio of the AD poor prognosis group was significantly lower than the NAA/Cr ratio of the good prognosis group. The decrease in NAA/Cr ratio indicates that there is more loss of bilateral hippocampal neurons, which can be used as a biomarker for the transition from mild cognitive impairment to AD. Zhang et al. (Zhang et al., 2015) found that the NAA/Cr ratio of the posterior cingulate gyrus of MCI patients who progressed to AD dementia was lower than that of patients who progressed to Lewy body dementia (DLB). The prognosis of AD type dementia and DLB. Kantarci et al. (Kantarci et al., 2004) tested the cranial MRS of AD, VD, and DLB patients and found that NAA/Cr in AD and VD patients were lower than normal. AD patients had NAA/Cr lower than DLB patients. The Cho/Cr ratio of AD and DLB patients was higher than normal. The researcher believe that in dementia characterized by neuronal loss, NAA/Cr ratio is reduced, and in dementia characterized by severe cholinergic insufficiency, Cho/Cr ratio is elevated. By examining the cranial MRS of AD patients, it can not only be used to diagnose AD, but also be used to evaluate the prognosis of AD patients.
EEG examination is mainly used for differential diagnosis of epilepsy, as well as auxiliary diagnosis of encephalitis and certain encephalopathy (Bagattini et al., 2019). This study also found that the prognosis of AD patients with a ratio of (θ+δ)/(α+β) greater than or equal to 1. showed that the area under the curve was 0.78, the corresponding sensitivity was 71%, and the specificity was 69%. Researcher believe these SCD and MCI patients are at high risk of developing dementia within five years. Our study also found that the clinical prognosis of AD patients with severe depressive symptoms, moderate or severe brain atrophy, and severe abnormal EEG is poor. These aspects need to be grasped as a whole and further analyzed. Olichney et al. (Olichney et al., 2008) believed that when abnormal N400 and P600 repeat effects were detected by cognitive event related potential (ERP) in AD patients, it indicated that the synaptic plasticity in the brain of the patients had been significantly abnormal. Abnormalities of P600 or N400 in MCI patients are significantly associated with an increased risk of subsequent conversion to AD, and ERP test could provide a useful biomarker for the diagnosis of AD patients.
NLR is considered to be an easy to detect and operate systemic inflammatory index, which is related to the abnormal cellular immune function. Based on the above considerations, we analyzed the impact of NLR on the prognosis of AD patients. The results showed that there was no significant correlation between the ratio of NLR in blood and the prognosis of AD patients. Rembach et al. (2014) found that the sensitivity of NLR itself is not enough to diagnose AD.
There is indeed a certain correlation between NLR and neocortical amyloid load in the cross section, but this relationship disappeared after longitudinal analysis. Moreover, the association between NLR and cognitive decline is also limited. They believe that NLR may only reflect the peripheral blood related inflammatory process, which is greatly affected by age and gender. These immunoglobulin test were not carried out. Third, the sample size of this study is relatively small, and it is a single institution study, and the popularization value of the conclusion is limited.
Nevertheless, this research still has some valuable findings in predicting the correlation between abnormal cellular immune function and poor prognosis in AD patients.

Conclusion
The decrease in the proportion of T lymphocytes may have predictive value for the poor prognosis of AD. It is suggested that the proportion of T lymphocytes less than 55% should be used as the cut-off threshold for predicting the poor prognosis of AD. In addition, MRS combined with EEG detection is also worthy of recognition in predicting the poor prognosis of AD. Yet the early and continuous drug treatment that improve cognitive function is associated with a good prognosis.