Background The objectives of this study were to delineate whether delirium in older adults is associated with activation of the immune-inflammatory response system (IRS) as indicated by activation of M1, T helper (Th)1, and Th17 profiles, and/or by reduced activities of the compensatory immunoregulatory system (CIRS), including Th2 and T regulatory profiles. Methods We recruited 65 older adult patients with a low energy impact hip fracture who underwent hip fracture operation. The CAM-ICU and the Delirium Rating Scale, Revised-98-Thai version (DRS-R-98) were assessed pre-operatively and 1, 2 and 3 days after surgery. Blood samples (day 1 and 2) post-surgery were assayed for cytokines/chemokines using a MultiPlex assay and the neutrophil/lymphocyte ratio. Results We found that delirium and/or the DRS-R-98 score were associated with IRS activation as indicated by activated M1, Th1, Th17 and T cell growth profiles and by attenuated CIRS functions. The most important IRS biomarkers were CXCL8, interleukin (IL)-6, and tumor necrosis factor-α, and the most important CIRS biomarkers were IL-4 and soluble IL-1 receptor antagonist. We found that 42.5% of the variance in the actual changes in the DRS-R-98 score (averaged from day 1 to day 3) was explained by T cell growth factors, baseline DRS-R-98 scores and age. An increase in the NLR reflects overall IRS, M1, Th1, Th17, and Th2 activation. Conclusions Post-hip surgery delirium is associated with activated IRS pathways and appears especially in patients with lowered CIRS functions.

<b><i>Background:</i></b> Postoperative delirium in elderly people with hip fracture is associated with various adverse clinical outcomes. Nevertheless, the pathophysiological processes underpinning delirium have remained elusive. <b><i>Objectives:</i></b> The aim of this study was to explore the associations between delirium and its features and immune-inflammatory and blood gas biomarkers. <b><i>Methods:</i></b> In this prospective study, we examined 65 patients who underwent a hip fracture surgery and assessed the Confusion Assessment Method for the Intensive Care Unit, Richmond Agitation-Sedation Scale (RASS), and Delirium Rating Scale Revised-98 (DRS-R-98) before and during 4 days after the surgery. Complete blood count and venous blood gas markers were obtained at the same time points. <b><i>Results:</i></b> Delirium was observed in 19 patients and was accompanied by significantly increased pO₂, number of white blood cells, neutrophil percentage, and neutrophil/lymphocyte ratio, and lower mean platelet volume (MPV) after adjusting for age, central nervous system (CNS) disease, blood loss during surgery, sleep disorders, and body mass index. The severity of delirium was associated with lowered number of platelets and MPV. Psychomotor disorders were associated with lower bicarbonate levels. The requirement of physical restraint of the patients was predicted by increased percentages of neutrophils and lymphocytes. Prior CNS disease was together with these biomarkers a significant predictor of delirium and severity of delirium. <b><i>Conclusion:</i></b> Delirium and psychomotor disorders following hip fracture and surgery may be caused by immune-inflammatory and oxidative stress pathways probably attributable to an aseptic inflammatory process.

Background: There is now evidence that affective disorders including major depressive disorder (MDD) and bipolar disorder (BD) are mediated by immune-inflammatory and nitro-oxidative pathways. Activation of these pathways may be associated with activation of the tryptophan catabolite (TRYCAT) pathway leading to depletion of tryptophan (TRP) and increases in tryptophan catabolites (TRYCATs). Aims: To systematically review and meta-analyze TRP, its competing amino-acids (CAAs) and TRYCAT data in MDD and BD. Methods: This review searched PubMed, Google Scholar and SciFinder and included 121 full-text articles and 15470 individuals, including 8024 MDD/BD patients and 7446 healthy controls. Results: TRP levels (either free and total) and the TRP/CAAs ratio were significantly decreased (p<0.0001) in MDD/BD as compared with controls with a moderate effect size (standardized mean difference for TRP: SMD=-0.513, 95% confidence interval, CI: -0.611; -0.414; and TRP/CAAs: SMD=-0.558, CI: -0.758; -0.358). Kynurenine (KYN) levels were significantly decreased in patients as compared with controls with a small effect size (p<0.0001, SMD= -0.213, 95%CI: -0.295; -0.131). These differences were significant in plasma (p<0.0001, SMD=-0.304, 95%CI: -0.415, -0.194) but not in serum (p=0.054) or the central nervous system (CNS, p=0.771). The KYN/TRP ratio, frequently used as an index of indoleamine-dioxygenase (IDO) activity, and neurotoxicity indices based on downstream TRYCATs were unaltered or even lowered in MDD/BD. Conclusions: Our findings revealed that MDD/BD are accompanied by TRP depletion without IDO and TRYCAT pathway activation. Lowered TRP availability is probably the consequence of lowered serum albumin during the inflammatory response in affective disorders.

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Major depressive disorder (MDD) and bipolar disorder (BD) with melancholia and psychotic features and suicidal behaviors are accompanied by activated immune-inflammatory and oxidative pathways, which may stimulate indoleamine 2,3-dioxygenase (IDO), the first and rate-limiting enzyme of the tryptophan catabolite (TRYCAT) pathway resulting in increased tryptophan degradation and elevated tryptophan catabolites (TRYCTAs). The purpose of the current study is to systematically review and meta-analyze levels of TRP, its competing amino acids (CAAs) and TRYCATs in patients with severe affective disorders. Methods: PubMed, Google Scholar and SciFinder were searched in the present study and we recruited 35 studies to examine 4647 participants including 2332 unipolar (MDD) and bipolar (BD) depressed patients and 2315 healthy controls. Severe patients showed significant lower (p < 0.0001) TRP (standardized mean difference, SMD = −0.517, 95% confidence interval, CI: −0.735; −0.299) and TRP/CAAs (SMD= −0.617, CI: −0.957; −0.277) levels with moderate effect sizes, while no significant difference in CAAs were found. Kynurenine (KYN) levels were unaltered in severe MDD/BD phenotypes, while the KYN/TRP ratio showed a significant increase only in patients with psychotic features (SMD= 0.224, CI: 0.012; 0.436). Quinolinic acid (QA) was significantly increased (SMD= 0.358, CI: 0.015; 0.701) and kynurenic acid (KA) significantly decreased (SMD= −0.260, CI: −0.487; −0.034) in severe MDD/BD. Patients with affective disorders with melancholic and psychotic features and suicidal behaviors showed normal IDO enzyme activity but a lowered availability of plasma/serum TRP to the brain, which is probably due to other processes such as low albumin levels.