We report the large-scale use of compositional data analysis to establish a baseline microbiota composition in an extremely healthy cohort of the Chinese population. This baseline will serve for comparison for future cohorts with chronic or acute disease. In addition to the expected difference in the microbiota of children and adults, we found that the microbiota of the elderly in this population was similar in almost all respects to that of healthy people in the same population who are scores of years younger. We speculate that this similarity is a consequence of an active healthy lifestyle and diet, although cause and effect cannot be ascribed in this (or any other) cross-sectional design. One surprising result was that the gut microbiota of persons in their 20s was distinct from those of other age cohorts, and this result was replicated, suggesting that it is a reproducible finding and distinct from those of other populations.

IL-6 is both necessary and sufficient to produce cognitive decline. Following further preclinical testing of its perioperative safety, the IL6R blocker tocilizumab is a candidate for prevention and/or treatment of PND.

BACKGROUND Dexmedetomidine is known to be a sedative. Recent studies suggest that administration of dexmedetomidine can prevent postoperative delirium (POD) which has been confirmed as a common complication after major surgery. However, its effects in patients undergoing oesophagectomy are scarce. OBJECTIVE To investigate the efficacy and safety of dexmedetomidine in reducing POD in elderly patients after transthoracic oesophagectomy with total intravenous anaesthesia (TIVA). DESIGN A randomised, double-blind, placebo-controlled trial. SETTING Single-centre, tertiary care hospital, November 2016 to September 2018. PATIENTS Eligible patients (n = 177) undergoing transthoracic oesophagectomy were randomly assigned to receive total intravenous anaesthesia (TIVA, n = 87) or dexmedetomidine with TIVA (DEX-TIVA, n = 90). INTERVENTIONS Patients receiving DEX-TIVA received a loading dose of dexmedetomidine (0.4 μg kg−1), over 15 min, followed by a continuous infusion at a rate of 0.1 μg kg−1 h−1 until 1 h before the end of surgery. Patients receiving TIVA received physiological saline with a similar infusion rate protocol. OUTCOME MEASURES The primary outcome was the incidence of POD. The secondary endpoints were the incidence of emergence agitation, serum interleukin-6 (IL-6) levels and haemodynamic profile. RESULTS All randomised patients were included with planned intention-to-treat analyses for POD. Delirium occurred in 15 (16.7%) of 90 cases given dexmedetomidine, and in 32 (36.8%) of 87 cases given saline (P = 0.0036). The DEX-TIVA group showed less frequent emergence agitation than the TIVA group (22.1 vs. 48.0%, P = 0.0058). The incremental change in surgery-induced IL-6 levels was greater in the TIVA group than DEX-TIVA group (P < 0.0001). CONCLUSION Adding peri-operative dexmedetomidine to a total intravenous anaesthetic safely reduces POD and emergence agitation in elderly patients undergoing open transthoracic oesophagectomy. These benefits were associated with a postoperative reduction in circulating levels of the pro-inflammatory cytokine IL-6 and stabilisation of the haemodynamic profile. TRIAL REGISTRATION Chinese Clinical Trials Register Identifier: ChiCTR-IPR-17010881.

Background Inflammation initiated by damage-associated molecular patterns has been implicated for the cognitive decline associated with surgical trauma and serious illness. We determined whether resolution of inflammation mediates dexmedetomidine-induced reduction of damage-associated molecular pattern–induced cognitive decline. Methods Cognitive decline (assessed by trace fear conditioning) was induced with high molecular group box 1 protein, a damage-associated molecular pattern, in mice that also received blockers of neural (vagal) and humoral inflammation-resolving pathways. Systemic and neuroinflammation was assessed by proinflammatory cytokines. Results Damage-associated molecular pattern–induced cognitive decline and inflammation (mean ± SD) was reversed by dexmedetomidine (trace fear conditioning: 58.77 ± 8.69% vs. 41.45 ± 7.64%, P &lt; 0.0001; plasma interleukin [IL]-1β: 7.0 ± 2.2 pg/ml vs. 49.8 ± 6.0 pg/ml, P &lt; 0.0001; plasma IL-6: 3.2 ± 1.6 pg/ml vs. 19.5 ± 1.7 pg/ml, P &lt; 0.0001; hippocampal IL-1β: 4.1 ± 3.0 pg/mg vs. 41.6 ± 8.0 pg/mg, P &lt; 0.0001; hippocampal IL-6: 3.4 ± 1.3 pg/mg vs. 16.2 ± 2.7 pg/mg, P &lt; 0.0001). Reversal by dexmedetomidine was prevented by blockade of vagomimetic imidazoline and α7 nicotinic acetylcholine receptors but not by α2 adrenoceptor blockade. Netrin-1, the orchestrator of inflammation–resolution, was upregulated (fold-change) by dexmedetomidine (lung: 1.5 ± 0.1 vs. 0.7 ± 0.1, P &lt; 0.0001; spleen: 1.5 ± 0.2 vs. 0.6 ± 0.2, P &lt; 0.0001), resulting in upregulation of proresolving (lipoxin-A4: 1.7 ± 0.2 vs. 0.9 ± 0.2, P &lt; 0.0001) and downregulation of proinflammatory (leukotriene-B4: 1.0 ± 0.2 vs. 3.0 ± 0.3, P &lt; 0.0001) humoral mediators that was prevented by α7 nicotinic acetylcholine receptor blockade. Conclusions Dexmedetomidine resolves inflammation through vagomimetic (neural) and humoral pathways, thereby preventing damage-associated molecular pattern–mediated cognitive decline.

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Summary Overdispersion and structural zeros are two major manifestations of departure from the Poisson assumption when modeling count responses using Poisson loglinear regression. As noted in a large body of literature, ignoring such departures could yield bias and lead to wrong conclusions. Different approaches have been developed to tackle these two major problems. In this paper, we review available methods for dealing with overdispersion and structural zeros within a longitudinal data setting and propose a distribution-free modeling approach to address the limitations of these methods by utilizing a new class of functional response models (FRM). We illustrate our approach with both simulated and real study data.

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