High intensity interval training as a novel treatment for impaired awareness of hypoglycaemia in people with type 1 diabetes (HIT4HYPOS): a randomised parallel-group study

AIMS/HYPOTHESIS

Impaired awareness of hypoglycaemia (IAH) in type 1 diabetes may develop through a process referred to as habituation. Consistent with this, a single bout of high intensity interval exercise as a novel stress stimulus improves counterregulatory responses (CRR) to next-day hypoglycaemia, referred to as dishabituation. This longitudinal pilot study investigated whether 4 weeks of high intensity interval training (HIIT) has sustained effects on counterregulatory and symptom responses to hypoglycaemia in adults with type 1 diabetes and IAH.

METHODS

HIT4HYPOS was a single-centre, randomised, parallel-group study. Participants were identified using the Scottish Diabetes Research Network (SDRN) and from diabetes outpatient clinics in NHS Tayside, UK. The study took place at the Clinical Research Centre, Ninewells Hospital and Medical School, Dundee, UK. Participants were aged 18-55 years with type 1 diabetes of at least 5 years' duration and HbA1c levels <75 mmol/mol (<9%). They had IAH confirmed by a Gold score ≥4, modified Clarke score ≥4 or Dose Adjustment For Normal Eating [DAFNE] hypoglycaemia awareness rating of 2 or 3, and/or evidence of recurrent hypoglycaemia on flash glucose monitoring. Participants were randomly allocated using a web-based system to either 4 weeks of real-time continuous glucose monitoring (RT-CGM) or RT-CGM+HIIT. Participants and investigators were not masked to group assignment. The HIIT programme was performed for 20 min on a stationary exercise bike three times a week. Hyperinsulinaemic-hypoglycaemic (2.5 mmol/l) clamp studies with assessment of symptoms, hormones and cognitive function were performed at baseline and after 4 weeks of the study intervention. The predefined primary outcome was the difference in hypoglycaemia-induced adrenaline (epinephrine) responses from baseline following RT-CGM or RT-CGM+HIIT.

RESULTS

Eighteen participants (nine men and nine women) with type 1 diabetes (median [IQR] duration 27 [18.75-32] years) and IAH were included, with nine participants randomised to each group. Data from all study participants were included in the analysis. During the 4 week intervention there were no significant mean (SEM) differences between RT-CGM and RT-CGM+HIIT in exposure to level 1 (28 [7] vs 22 [4] episodes, p=0.45) or level 2 (9 [3] vs 4 [1] episodes, p=0.29) hypoglycaemia. The CGM-derived mean glucose level, SD of glucose and glucose management indicator (GMI) did not differ between groups. During the hyperinsulinaemic-hypoglycaemic clamp studies, mean (SEM) change from baseline was greater for the noradrenergic responses (RT-CGM vs RT-CGM+HIIT: -988 [447] vs 514 [732] pmol/l, p=0.02) but not the adrenergic responses (-298 [687] vs 1130 [747] pmol/l, p=0.11) in those participants who had undergone RT-CGM+HIIT. There was a benefit of RT-CGM+HIIT for mean (SEM) change from baseline in the glucagon CRR to hypoglycaemia (RT-CGM vs RT-CGM+HIIT: 1 [4] vs 16 [6] ng/l, p=0.01). Consistent with the hormone response, the mean (SEM) symptomatic response to hypoglycaemia (adjusted for baseline) was greater following RT-CGM+HIIT (RT-CGM vs RT-CGM+HIIT: -4 [2] vs 0 [2], p<0.05).

CONCLUSIONS/INTERPRETATION

In this pilot clinical trial in people with type 1 diabetes and IAH, we found continuing benefits of HIIT for overall hormonal and symptomatic CRR to subsequent hypoglycaemia. Our findings also suggest that HIIT may improve the glucagon response to insulin-induced hypoglycaemia.

TRIAL REGISTRATION

ISRCTN15373978.

FUNDING

Sir George Alberti Fellowship from Diabetes UK (CMF) and the Juvenile Diabetes Research Foundation.

Cardiovascular Safety in Type 2 Diabetes With Sulfonylureas as Second-Line Drugs: A Nation-Wide Population-Based Comparative Safety Study

OBJECTIVE

To assess the real-world cardiovascular (CV) safety for sulfonylureas (SU), in comparison with dipeptidylpeptidase-4 inhibitors (DPP4i) and thiazolidinediones (TZD), through development of robust methodology for causal inference in a whole nation study.

RESEARCH DESIGN AND METHODS

A cohort study was performed including people with type 2 diabetes diagnosed in Scotland before 31 December 2017, who failed to reach HbA1c 48 mmol/mol despite metformin monotherapy and initiated second-line pharmacotherapy (SU/DPP4i/TZD) on or after 1 January 2010. The primary outcome was composite major adverse cardiovascular events (MACE), including hospitalization for myocardial infarction, ischemic stroke, heart failure, and CV death. Secondary outcomes were each individual end point and all-cause death. Multivariable Cox proportional hazards regression and an instrumental variable (IV) approach were used to control confounding in a similar way to the randomization process in a randomized control trial.

RESULTS

Comparing SU to non-SU (DPP4i/TZD), the hazard ratio (HR) for MACE was 1.00 (95% CI: 0.91-1.09) from the multivariable Cox regression and 1.02 (0.91-1.13) and 1.03 (0.91-1.16) using two different IVs. For all-cause death, the HR from Cox regression and the two IV analyses was 1.03 (0.94-1.13), 1.04 (0.93-1.17), and 1.03 (0.90-1.17).

CONCLUSIONS

Our findings contribute to the understanding that second-line SU for glucose lowering are unlikely to increase CV risk or all-cause mortality. Given their potent efficacy, microvascular benefits, cost effectiveness, and widespread use, this study supports that SU should remain a part of the global diabetes treatment portfolio.

Glycated Haemoglobin A1c Variability Score Elicits Kidney Function Decline in Chinese People Living with Type 2 Diabetes

Our aim was to investigate the association of glycated haemoglobin A1c (HbA1c) variability score (HVS) with estimated glomerular filtration rate (eGFR) slope in Chinese adults living with type 2 diabetes. This cohort study included adults with type 2 diabetes attending outpatient clinics between 2011 and 2019 from a large electronic medical record-based database of diabetes in China (WECODe). We estimated the individual-level visit-to-visit HbA1c variability using HVS, a proportion of changes in HbA1c of ≥0.5% (5.5 mmol/mol). We estimated the odds of people experiencing a rapid eGFR annual decline using a logistic regression and differences across HVS categories in the mean eGFR slope using a mixed-effect model. The analysis involved 2397 individuals and a median follow-up of 4.7 years. Compared with people with HVS ≤ 20%, those with HVS of 60% to 80% had 11% higher odds of experiencing rapid eGFR annual decline, with an extra eGFR decline of 0.93 mL/min/1.73 m2 per year on average; those with HVS > 80% showed 26% higher odds of experiencing a rapid eGFR annual decline, with an extra decline of 1.83 mL/min/1.73 m2 per year on average. Chinese adults with type 2 diabetes and HVS > 60% could experience a more rapid eGFR decline.

Heterogeneity in phenotype, disease progression and drug response in type 2 diabetes

Type 2 diabetes (T2D) is a complex chronic disease characterized by considerable phenotypic heterogeneity. In this study, we applied a reverse graph embedding method to routinely collected data from 23,137 Scottish patients with newly diagnosed diabetes to visualize this heterogeneity and used partitioned diabetes polygenic risk scores to gain insight into the underlying biological processes. Overlaying risk of progression to outcomes of insulin requirement, chronic kidney disease, referable diabetic retinopathy and major adverse cardiovascular events, we show how these risks differ by patient phenotype. For example, patients at risk of retinopathy are phenotypically different from those at risk of cardiovascular events. We replicated our findings in the UK Biobank and the ADOPT clinical trial, also showing that the pattern of diabetes drug monotherapy response differs for different drugs. Overall, our analysis highlights how, in a European population, underlying phenotypic variation drives T2D onset and affects subsequent diabetes outcomes and drug response, demonstrating the need to incorporate these factors into personalized treatment approaches for the management of T2D.

145 Best Medical Therapy for Patients with Peripheral Arterial Disease: A Quality Improvement Project in Vascular Surgery, Aberdeen Royal Infirmary

Introduction

Peripheral arterial disease (PAD) is the leading cause of limb amputation and cardiovascular morbidity. The National Institute for Health and Care Excellence (NICE) advocates best medical therapy (BMT) with high-dose statin (atorvastatin 80mg) and antiplatelets (clopidogrel or aspirin) for secondary prevention in patients with PAD. We assessed compliance to BMT prescribing in our vascular department.

Method

Retrospective data were collected for all patients admitted with symptomatic PAD in our vascular department over a 2-week period. Criteria for BMT were as per NICE guidelines with a standard set to 100%. Following cycle 1, a new admission document prompting antiplatelet and statin review was designed and departmental teaching on BMT delivered. Standard compliance was re-audited after 3 months.

Results

Twenty-five patients were admitted with PAD during cycle 1 with 28% of patients (n = 7) on BMT on admission. This increased to 40% (n = 10) on discharge with 100% (n = 25) on an antiplatelet and 28% (n = 7) on high-dose statin. Overall, there were twenty patients in cycle 2 with 25% of patients (n = 5) on BMT on admission. This increased to 80% (n = 16) on discharge with 100% (n = 20) on an antiplatelet and 80% (n = 16) on high-dose statin.

Conclusions

Our data demonstrated poor implementation of BMT for patients with PAD managed in primary care suggesting a need for primary care education. Adaption of our admission proforma to prompt BMT prescribing as well as departmental teaching was associated with drastic improvement of BMT prescription on discharge and standard adherence.

Understanding health-care outcomes of older people with cognitive impairment and/or dementia admitted to hospital: a mixed-methods study

Background

Cognitive impairment is common in older people admitted to hospital, but previous research has focused on single conditions.

Objective

This project sits in phase 0/1 of the Medical Research Council Framework for the Development and Evaluation of Complex Interventions. It aims to develop an understanding of current health-care outcomes. This will be used in the future development of a multidomain intervention for people with confusion (dementia and cognitive impairment) in general hospitals. The research was conducted from January 2015 to June 2018 and used data from people admitted between 2012 and 2013.

Design

For the review of outcomes, the systematic review identified peer-reviewed quantitative epidemiology measuring prevalence and associations with outcomes. Screening for duplication and relevance was followed by full-text review, quality assessment and a narrative review (141 papers). A survey sought opinion on the key outcomes for people with dementia and/or confusion and their carers in the acute hospital (n = 78). For the analysis of outcomes including cost, the prospective cohort study was in a medical admissions unit in an acute hospital in one Scottish health board covering 10% of the Scottish population. The participants (n = 6724) were older people (aged ≥ 65 years) with or without a cognitive spectrum disorder who were admitted as medical emergencies between January 2012 and December 2013 and who underwent a structured nurse assessment. ‘Cognitive spectrum disorder’ was defined as any combination of delirium, known dementia or an Abbreviated Mental Test score of < 8 out of 10 points. The main outcome measures were living at home 30 days after discharge, mortality within 2 years of admission, length of stay, re-admission within 2 years of admission and cost.

Data sources

Scottish Morbidity Records 01 was linked to the Older Persons Routine Acute Assessment data set.

Results

In the systematic review, methodological heterogeneity, especially concerning diagnostic criteria, means that there is significant overlap in conditions of patients presenting to general hospitals with confusion. Patients and their families expect that patients are discharged in the same or a better condition than they were in on admission or, failing that, that they have a satisfactory experience of their admission. Cognitive spectrum disorders were present in more than one-third of patients aged ≥ 65 years, and in over half of those aged ≥ 85 years. Outcomes were worse in those patients with cognitive spectrum disorders than in those without: length of stay 25.0 vs. 11.8 days, 30-day mortality 13.6% vs. 9.0%, 1-year mortality 40.0% vs. 26.0%, 1-year mortality or re-admission 62.4% vs. 51.5%, respectively (all p < 0.01). There was relatively little difference by cognitive spectrum disorder type; for example, the presence of any cognitive spectrum disorder was associated with an increased mortality over the entire period of follow-up, but with different temporal patterns depending on the type of cognitive spectrum disorder. The cost of admission was higher for those with cognitive spectrum disorders, but the average daily cost was lower.

Limitations

A lack of diagnosis and/or standardisation of diagnosis for dementia and/or delirium was a limitation for the systematic review, the quantitative study and the economic study. The economic study was limited to in-hospital costs as data for social or informal care costs were unavailable. The survey was conducted online, limiting its reach to older carers and those people with cognitive spectrum disorders.

Conclusions

Cognitive spectrum disorders are common in older inpatients and are associated with considerably worse health-care outcomes, with significant overlap between individual cognitive spectrum disorders. This suggests the need for health-care systems to systematically identify and develop care pathways for older people with cognitive spectrum disorders, and avoid focusing on only condition-specific pathways.

Future work

Development and evaluation of a multidomain intervention for the management of patients with cognitive spectrum disorders in hospital.

Study registration

This study is registered as PROSPERO CRD42015024492.

Funding

This project was funded by the National Institute for Health Research (NIHR) Health Services and Delivery Research programme and will be published in full in Health Services and Delivery Research; Vol. 9, No. 8. See the NIHR Journals Library website for further project information.

The Relationship between AKI and CKD in Patients with Type 2 Diabetes: An Observational Cohort Study

BACKGROUND

There are few observational studies evaluating the risk of AKI in people with type 2 diabetes, and even fewer simultaneously investigating AKI and CKD in this population. This limits understanding of the interplay between AKI and CKD in people with type 2 diabetes compared with the nondiabetic population.

METHODS

In this retrospective, cohort study of participants with or without type 2 diabetes, we used electronic healthcare records to evaluate rates of AKI and various statistical methods to determine their relationship to CKD status and further renal function decline.

RESULTS

We followed the cohort of 16,700 participants (9417 with type 2 diabetes and 7283 controls without diabetes) for a median of 8.2 years. Those with diabetes were more likely than controls to develop AKI (48.6% versus 17.2%, respectively) and have preexisting CKD or CKD that developed during follow-up (46.3% versus 17.2%, respectively). In the absence of CKD, the AKI rate among people with diabetes was nearly five times that of controls (121.5 versus 24.6 per 1000 person-years). Among participants with CKD, AKI rate in people with diabetes was more than twice that of controls (384.8 versus 180.0 per 1000 person-years after CKD diagnostic date, and 109.3 versus 47.4 per 1000 person-years before CKD onset in those developing CKD after recruitment). Decline in eGFR slope before AKI episodes was steeper in people with diabetes versus controls. After AKI episodes, decline in eGFR slope became steeper in people without diabetes, but not among those with diabetes and preexisting CKD.

CONCLUSIONS

Patients with diabetes have significantly higher rates of AKI compared with patients without diabetes, and this remains true for individuals with preexisting CKD.

Quinine exposure and the risk of acute kidney injury: a population-based observational study of older people

Objectives

to establish and quantify any observable association between the exposure to community prescriptions for quinine and acute kidney injury (AKI) events in a population of older adults.

Design

two observational studies using the same dataset, a retrospective longitudinal cohort study and a self-controlled case series (SCCS).

Setting

NHS health board in Scotland.

Participants

older adults (60+ years) who received quinine prescriptions in Tayside, Scotland, between January 2004 and December 2015. The first study included 12,744 individuals. The SCCS cohort included 5,907 people with quinine exposure and more than or equal to one AKI event.

Main outcome measured

in the first study, multivariable logistic regression was used to calculate odds ratios (ORs) for AKI comparing between episodes with and without recent quinine exposure after adjustment for demographics, comorbidities and concomitant medications. The SCCS study divided follow-up for each individual into periods ‘on’ and ‘off’ quinine, calculating incidence rate ratios (IRRs) for AKI adjusting for age.

Results

during the study period, 273,596 prescriptions for quinine were dispensed in Tayside. A total of 13,616 AKI events occurred during follow-up (crude incidence 12.5 per 100 person-years). In the first study, exposure to quinine before an episode of care was significantly associated with an increased probability of AKI (adjusted OR = 1.27, 95% confidence interval (CI) 1.21–1.33). In the SCCS study, exposure to quinine was associated with an increased relative incidence of AKI compared to unexposed periods (IRR = 1.20, 95% CI 1.15–1.26), with the greatest risk observed within 30 days following quinine initiation (IRR = 1.48, 95% CI 1.35–1.61).

Conclusion

community prescriptions for quinine in an older adult population are associated with an increased risk of AKI.

P0578QUININE EXPOSURE AND THE RISK OF ACUTE KIDNEY INJURY: A POPULATION BASED OBSERVATIONAL STUDY OF OLDER PEOPLE

Background and Aims

Quinine can precipitate Acute Kidney Injury (AKI) by immune-mediated reactions. Cramps, for which quinine is traditionally prescribed, may be a symptom of conditions that are risk factors for AKI. The relationship between quinine and AKI at a population level is unclear. The aim of this study was to establish and quantify any observable association between the exposure to community prescriptions for quinine and AKI events in a population of older adults.

Method

We performed two observational studies of older adults (60+ years) who received quinine prescriptions in Tayside, Scotland, between January 2004 and December 2015. The first study was a retrospective longitudinal cohort study with the primary outcome AKI. Creatinine measurements less than seven days apart were grouped as episodes of care. Multivariable logistic regression was used to calculate odds ratios (OR) for AKI comparing between episodes with and without recent quinine exposure after adjustment for demographics, comorbidities and concomitant medications. A self-controlled case series (SCCS) was then conducted with follow-up divided into periods “on” and “off” quinine for the same individual, calculating incidence rate ratios (IRR) for AKI adjusting for age.

Results

The first study included 12,744 individuals who experienced 13,616 AKI events during cohort follow-up (crude incidence 12.5 per 100 person-years). Exposure to quinine before an episode of care was significantly associated with an increased probability of AKI (adjusted OR=1.27, 95% CI 1.21-1.33). The SCCS cohort included 5,907 people with quinine exposure with ≥1 AKI event. Exposure to quinine was associated with an increased relative incidence of AKI compared to unexposed periods (IRR=1.20, 95% CI 1.15-1.26), with the greatest risk observed within 30 days of quinine initiation (IRR=1.48, 95% CI 1.35-1.61).

Conclusion

Exposure to quinine in patients aged 60 years and over was associated with an increased risk of AKI, the incidence of which is unlikely to simply be explained be immune-mediated reactions only. Further research is required to determine exact reasons for the increased risk of AKI.

Effect of multiple episodes of acute kidney injury on mortality: an observational study

Background

Patients who survive an episode of acute kidney injury (AKI) are more likely to have further episodes of AKI. AKI is associated with increased mortality, with a further increase with recurrent episodes. It is not clear whether this is due to AKI or as a result of other patient characteristics. The aim of this study was to establish whether recurrence of AKI is an independent risk factor for mortality or if excess mortality is explained by other factors.

Methods

This observational cohort study included adult people from the Tayside region of Scotland, with an episode of AKI between 1 January 2009 and 31 December 2009. AKI was defined using the creatinine-based Kidney Disease: Improving Global Outcomes definition. Associations between recurrent AKI and mortality were examined using a Cox proportional hazards model.

Results

Survival was worse in the group identified to have recurrent AKI compared with those with a single episode of AKI [hazard ratio = 1.49, 95% confidence interval (CI) 1.37-1.63; P < 0.001]. After adjustment for comorbidities, stage of reference AKI, sex, age, medicines that predispose to renal impairment or, in the 3 months prior to the reference AKI, deprivation and baseline estimated glomerular filtration rate (eGFR), recurrent AKI was independently associated with an increase in mortality (hazard ratio = 1.25, 95% CI 1.14-1.37; P < 0.001). Increasing stage of reference AKI, age, deprivation, baseline eGFR, male sex, previous myocardial infarction, cerebrovascular disease and diuretic use were all associated with an increased risk of mortality in patients with recurrent AKI.

Conclusions

Recurrent AKI is associated with increased mortality. After adjusting for patient characteristics, the increase in mortality is independently associated with recurrent AKI and is not solely explained by other risk factors.

Visit-to-Visit HbA1c Variability Is Associated With Cardiovascular Disease and Microvascular Complications in Patients With Newly Diagnosed Type 2 Diabetes

OBJECTIVE

To investigate the association between visit-to-visit HbA_1c variability and cardiovascular events and microvascular complications in patients with newly diagnosed type 2 diabetes.

RESEARCH DESIGN AND METHODS

This retrospective cohort study analyzed patients from Tayside and Fife in the Scottish Care Information-Diabetes Collaboration (SCI-DC) who were observable from the diagnosis of diabetes and had at least five HbA_1c measurements before the outcomes were evaluated. We used the previously reported HbA_1c variability score (HVS), calculated as the percentage of the number of changes in HbA_1c >0.5% (5.5 mmol/mol) among all HbA_1c measurements within an individual. The association between HVS and 10 outcomes was assessed using Cox proportional hazards models.

RESULTS

We included 13,111-19,883 patients in the analyses of each outcome. The patients with HVS >60% were associated with elevated risks of all outcomes compared with the lowest quintile (for example, HVS >80 to ≤100 vs. HVS ≥0 to ≤20, hazard ratio 2.38 [95% CI 1.61-3.53] for major adverse cardiovascular events, 2.4 [1.72-3.33] for all-cause mortality, 2.4 [1.13-5.11] for atherosclerotic cardiovascular death, 2.63 [1.81-3.84] for coronary artery disease, 2.04 [1.12-3.73] for ischemic stroke, 3.23 [1.76-5.93] for heart failure, 7.4 [3.84-14.27] for diabetic retinopathy, 3.07 [2.23-4.22] for diabetic peripheral neuropathy, 5.24 [2.61-10.49] for diabetic foot ulcer, and 3.49 [2.47-4.95] for new-onset chronic kidney disease). Four sensitivity analyses, including adjustment for time-weighted average HbA_1c, confirmed the robustness of the results.

CONCLUSIONS

Our study shows that higher HbA_1c variability is associated with increased risks of all-cause mortality, cardiovascular events, and microvascular complications of diabetes independently of high HbA_1c.

Are antidementia drugs associated with reduced mortality after a hospital emergency admission in the population with dementia aged 65 years and older?

Introduction

People with dementia experience poor outcomes after hospital admission, with mortality being particularly high. There is no cure for dementia; antidementia medications have been shown to improve cognition and function, but their effect on mortality in real-world settings is little known. This study examines associations between treatment with antidementia medication and mortality in older people with dementia after an emergency admission.

Methods

The design is a retrospective cohort study of people aged ≥65 years, with a diagnosis of dementia and an emergency hospital admission between 01/01/2010 and 31/12/2016. Two classes of antidementia medication were considered: the acetylcholinesterase inhibitors and memantine. Mortality was examined using a Cox proportional hazards model with time-varying covariates for the prescribing of antidementia medication before or on admission and during one-year follow-up, adjusted for demographics, comorbidity, and community prescribing including anticholinergic burden. Propensity score analysis was examined for treatment selection bias.

Results

There were 9142 patients with known dementia included in this study, of which 45.0% (n = 4110) received an antidementia medication before or on admission; 31.3% (n = 2864) were prescribed one of the acetylcholinesterase inhibitors, 8.7% (n = 798) memantine, and 4.9% (n = 448) both. 32.9% (n = 1352) of these patients died in the year after admission, compared to 42.7% (n = 2148) of those with no antidementia medication on admission. The Cox model showed a significant reduction in mortality in patients treated with acetylcholinesterase inhibitors (hazard ratio [HR] = 0.78, 95% CI 0.72–0.85) or memantine (HR = 0.75, 95% CI 0.66–0.86) or both (HR = 0.76, 95% CI 0.68–0.94). Sensitivity analysis by propensity score matching confirmed the associations between antidementia prescribing and reduced mortality.

Discussion

Treatment with antidementia medication is associated with a reduction in risk of death in the year after an emergency hospital admission. Further research is required to determine if there is a causal relationship between treatment and mortality, and whether “symptomatic” therapy for dementia does have a disease-modifying effect.

•

Mortality in older people admitted with dementia is very high after an emergency hospital admission with about 40% of them dying within one year from admission.

•

Less than half of patients admitted with dementia are in receipt of antidementia treatment on admission.

•

Risk of death is reduced in patients treated with antidementia medication at the time of acute admission, which is not explained by their age, sex, comorbidities, or other drug prescribing.

Mortality in people with dementia, delirium, and unspecified cognitive impairment in the general hospital: prospective cohort study of 6,724 patients with 2 years follow-up

Purpose

Cognitive impairment is common in older people admitted to hospital, but the outcomes are generally poorly understood, and previous research has shown inconsistent associations with mortality depending on the type of cognitive impairment examined and duration of follow-up. This study examines mortality in older people with any cognitive impairment during acute hospital admission.

Patients and methods

Prospective cohort of 6,724 people aged ≥65 years with a structured cognitive assessment on acute admission were included in this study. Cognitive spectrum disorder (CSD) was defined as delirium alone, known dementia alone, delirium superimposed on known dementia, or unspecified cognitive impairment. Mortality associated with different types of CSD was examined using a non-proportional hazards model with 2-year follow-up.

Results

On admission, 35.4% of patients had CSD, of which 52.6% died within 2 years. After adjustment for demographics and comorbidity, delirium alone was associated with increased mortality in the 6 months post-admission (HR =1.45, 95% CI 1.28-1.65) and again after 1 year (HR =1.44, 95% CI 1.17-1.77). Patients with known dementia (alone or with superimposed delirium) had increased mortality only after 3 months from admission (HR =1.85, 95% CI 1.56-2.18 and HR =1.80, 95% CI 1.52-2.14) compared with patients with unspecified cognitive impairment after 6 months (HR =1.55, 95% CI 1.21-1.99). Similar but partially attenuated associations were seen after adjustment for functional ability.

Conclusion

Mortality post-admission is high in older people with CSD. Immediate risk is highest in those with delirium, while dementia or unspecified cognitive impairment is associated with medium- to long-term risk. These findings suggest that individuals without dementia who develop delirium are more seriously ill (have required a larger acute insult in order to precipitate delirium) than those with pre-existing brain pathology (dementia). Further research to explain the mortality patterns observed is required in order to translate the findings into clinical care.

Emergent Properties of Microbial Activity in Heterogeneous Soil Microenvironments: Different Research Approaches Are Slowly Converging, Yet Major Challenges Remain

Over the last 60 years, soil microbiologists have accumulated a wealth of experimental data showing that the bulk, macroscopic parameters (e.g., granulometry, pH, soil organic matter, and biomass contents) commonly used to characterize soils provide insufficient information to describe quantitatively the activity of soil microorganisms and some of its outcomes, like the emission of greenhouse gasses. Clearly, new, more appropriate macroscopic parameters are needed, which reflect better the spatial heterogeneity of soils at the microscale (i.e., the pore scale) that is commensurate with the habitat of many microorganisms. For a long time, spectroscopic and microscopic tools were lacking to quantify processes at that scale, but major technological advances over the last 15 years have made suitable equipment available to researchers. In this context, the objective of the present article is to review progress achieved to date in the significant research program that has ensued. This program can be rationalized as a sequence of steps, namely the quantification and modeling of the physical-, (bio)chemical-, and microbiological properties of soils, the integration of these different perspectives into a unified theory, its upscaling to the macroscopic scale, and, eventually, the development of new approaches to measure macroscopic soil characteristics. At this stage, significant progress has been achieved on the physical front, and to a lesser extent on the (bio)chemical one as well, both in terms of experiments and modeling. With regard to the microbial aspects, although a lot of work has been devoted to the modeling of bacterial and fungal activity in soils at the pore scale, the appropriateness of model assumptions cannot be readily assessed because of the scarcity of relevant experimental data. For significant progress to be made, it is crucial to make sure that research on the microbial components of soil systems does not keep lagging behind the work on the physical and (bio)chemical characteristics. Concerning the subsequent steps in the program, very little integration of the various disciplinary perspectives has occurred so far, and, as a result, researchers have not yet been able to tackle the scaling up to the macroscopic level. Many challenges, some of them daunting, remain on the path ahead. Fortunately, a number of these challenges may be resolved by brand new measuring equipment that will become commercially available in the very near future.

Anomalous diffusion of heterogeneous populations characterized by normal diffusion at the individual level

The characterization of the dispersal of populations of non-identical individuals is relevant to most ecological and epidemiological processes. In practice, the movement is quantified by observing relatively few individuals, and averaging to estimate the rate of dispersal of the population as a whole. Here, we show that this can lead to serious errors in the predicted movement of the population if the individuals disperse at different rates. We develop a stochastic model for the diffusion of heterogeneous populations, inspired by the movement of the parasitic nematode Phasmarhabditis hermaphrodita. Direct observations of this nematode in homogeneous and heterogeneous environments reveal a large variation in individual behaviour within the population as reflected initially in the speed of the movement. Further statistical analysis shows that the movement is characterized by temporal correlations and in a heterogeneously structured environment the correlations that occur are of shorter range compared with those in a homogeneous environment. Therefore, by using the first-order correlated random walk techniques, we derive an effective diffusion coefficient for each individual, and show that there is a significant variation in this parameter among the population that follows a gamma distribution. Based on these findings, we build a new dispersal model in which we maintain the classical assumption that individual movement can be described by normal diffusion, but due to the variability in individual dispersal rates, the diffusion coefficient is not constant at the population level and follows a continuous distribution. The conclusions and methodology presented are relevant to any heterogeneous population of individuals with widely different diffusion rates.

Influence of substrate on the body-waving behaviour of nematodes

Abstract

The soil-dwelling nematodes Steinernema carpocapsae, S. scapterisci, S. feltiae, S. glaseri, Heterorhabditis bacteriophora, H. megidis, Phasmarhabditis hermaphrodita and Caenorhabditis elegans were placed on agar plates each containing four substrates (peat, sand, sandy loam and leaf litter). The body-waving behaviour of infective juveniles was recorded over a 10-day period in the presence or absence of an insect, Galleria mellonella, a susceptible host of some species. Body-waving behaviour differed amongst species and varied significantly in relation to substrate, time and the presence of G. mellonella. Steinernema carpocapsae showed body-waving behaviour more than other species and this tendency increased significantly with time. More S. carpocapsae were seen body waving on peat and leaf litter than on either sandy loam or sand. Conversely, sand promoted body waving in S. scapterisci. Body waving by C. elegans was more common on peat than on any of the other substrates. Heterorhabditis megidis, not previously known to body wave, did so in low numbers on peat and sandy loam. The remaining four species did not body wave. Previous work has shown that the presence of S. glaseri increases body waving by S. carpocapsae. We investigated whether substrate influenced this interaction and also included S. scapterisci in the study. The presence of S. glaseri significantly altered rates of body waving in S. carpocapsae and S. scapterisci in a way that was substrate-dependent. Our data suggest that body-waving behaviour is determined by substrate quality and differing body-waving behaviours may be a mechanism by which nematodes avoid competition.

Modelling nematode movement using time-fractional dynamics

We use a correlated random walk model in two dimensions to simulate the movement of the slug parasitic nematode Phasmarhabditis hermaphrodita in homogeneous environments. The model incorporates the observed statistical distributions of turning angle and speed derived from time-lapse studies of individual nematode trails. We identify strong temporal correlations between the turning angles and speed that preclude the case of a simple random walk in which successive steps are independent. These correlated random walks are appropriately modelled using an anomalous diffusion model, more precisely using a fractional sub-diffusion model for which the associated stochastic process is characterised by strong memory effects in the probability density function.

Movement of the nematode, Phasmarhabditis hermaphrodita, in a structurally heterogeneous environment

Abstract

We consider the effect of structural heterogeneity on the movement of the slug-parasitic nematode, Phasmarhabditis hermaphrodita. The study involves image recording and analysis of nematode movement on a homogeneous layer of technical agar compared to movement of nematodes in a structurally heterogeneous environment that was created by adding sand particles to the plates of agar. Features of nematode trail, such as speed, turning angle distribution, fractal dimension and mean square displacement, were calculated for each treatment. The presence of sand particles significantly reduced the speed of nematodes and affected the distribution of the turning angle with an increased tendency for moving forward or radically changing the direction of movement. Also, the power-law pattern of the mean square displacement changed, suggesting that nematode dispersal capacity became slower, from super-diffusive in homogeneous agar to sub-diffusive in the presence of sand particles. Further, the correlation in step length and turning angles was computed as a function of lags between steps and used to identify memory effects on nematode movement. While in the homogeneous environment movement was characterised by strong temporal correlations; the impact of sand particles was to reduce these correlations between steps. The results suggest that the presence of structural heterogeneity introduces a new bias into the movement, which plays an important role in complex environments where the nematode movement may be obstructed by soil particles.