Estimates of the Statistics of Randomly Varying Parameters of Linear Systems

Mathematical model used in estimating statistics of randomly varying parameters of linear system

KINETICS OF GELATIN HARDENING BY CERTAIN ALDEHYDE AND EPOXY HARDENERS IN CONCENTRATED MEDIA.

Study of the influence of gelatin concentration on the rate of its hardening by hardeners differing in activity showed that in the case of highly reactive hardeners in concentrated solutions the process is controlled by diffusion and the reaction rate falls sharply. In the case of hardeners of low reactivity the reaction rate is independent of concentration. The results obtained provide a link between the kinetic parameters of gelatin hardening in dilute and concentrated solutions, making it possible to calculate the time required for any specified degree of hardening in solutions of any concentration

KINETICS OF GELATIN HARDENING BY CERTAIN ALDEHYDE AND EPOXY HARDENERS IN CONCENTRATED MEDIA.

Study of the influence of gelatin concentration on the rate of its hardening by hardeners differing in activity showed that in the case of highly reactive hardeners in concentrated solutions the process is controlled by diffusion and the reaction rate falls sharply. In the case of hardeners of low reactivity the reaction rate is independent of concentration. The results obtained provide a link between the kinetic parameters of gelatin hardening in dilute and concentrated solutions, making it possible to calculate the time required for any specified degree of hardening in solutions of any concentration

Big data and data repurposing – using existing data to answer new questions in vascular dementia research

Introduction: Traditional approaches to clinical research have, as yet, failed to provide effective treatments for vascular dementia (VaD). Novel approaches to collation and synthesis of data may allow for time and cost efficient hypothesis generating and testing. These approaches may have particular utility in helping us understand and treat a complex condition such as VaD. Methods: We present an overview of new uses for existing data to progress VaD research. The overview is the result of consultation with various stakeholders, focused literature review and learning from the group’s experience of successful approaches to data repurposing. In particular, we benefitted from the expert discussion and input of delegates at the 9th International Congress on Vascular Dementia (Ljubljana, 16-18th October 2015). Results: We agreed on key areas that could be of relevance to VaD research: systematic review of existing studies; individual patient level analyses of existing trials and cohorts and linking electronic health record data to other datasets. We illustrated each theme with a case-study of an existing project that has utilised this approach. Conclusions: There are many opportunities for the VaD research community to make better use of existing data. The volume of potentially available data is increasing and the opportunities for using these resources to progress the VaD research agenda are exciting. Of course, these approaches come with inherent limitations and biases, as bigger datasets are not necessarily better datasets and maintaining rigour and critical analysis will be key to optimising data use

Risk factors and in-hospital outcomes in stroke and myocardial infarction patients

BACKGROUND: Acute stroke (AS) and acute myocardial infarction (AMI) share major risk factors such as age, gender, and high blood pressure. The main objective of this study was to compare vascular risk factor profiles with in-hospital outcomes in AS and AMI patients. METHODS: We evaluated 486 consecutive patients who were admitted to Bjelovar General Hospital with diagnoses of AS (ischaemic stroke or intracerebral haemorrhage; N = 380) or AMI (N = 106) during a one year period. The frequency of risk factors and in-patient mortality rates were assessed in both groups. For statistical analysis we used t-tests and χ(2 )tests. RESULTS: AS patients were significantly older than AMI patients: the mean age for AS patients was 68.9 ± 9.1 years, and for AMI patients was 62.8 ± 11.7 years (p < 0.001). AMI was significantly more common than AS in patients younger than 65 years; 51% of this group had AMI and 26% had AS (p < 0.001). Hypertension was a more common risk factor in AS patients (69% AS patients vs. 58% AMI patients; p = 0.042). Patients who died did not differ significantly in age between the groups. In-patient mortality rates were significantly higher in AS than AMI cases (31% vs. 12%, p < 0.001 for all patients; 37% vs.5%, p < 0.001 for men). Women hospitalized for AMI were more likely to die in hospital than men (28% vs. 5%; p = 0.002). CONCLUSIONS: We found that age at the time of presentation was a significant differentiating factor between patients with AS and AMI. The only exceptions were women, whose ages at the onset of AS and AMI were similar. In contrast, patients who died did not differ significantly in age. We observed significantly higher inpatient mortality for men (when adjusted for age) than for women with AS. The five-fold higher in-patient mortality rate in women than in men with AMI is most likely to have resulted from other factors related to treatment

Primary stroke prevention worldwide: translating evidence into action

Stroke is the second leading cause of death and the third leading cause of disability worldwide and its burden is increasing rapidly in low-income and middle-income countries, many of which are unable to face the challenges it imposes. In this Health Policy paper on primary stroke prevention, we provide an overview of the current situation regarding primary prevention services, estimate the cost of stroke and stroke prevention, and identify deficiencies in existing guidelines and gaps in primary prevention. We also offer a set of pragmatic solutions for implementation of primary stroke prevention, with an emphasis on the role of governments and population-wide strategies, including task-shifting and sharing and health system re-engineering. Implementation of primary stroke prevention involves patients, health professionals, funders, policy makers, implementation partners, and the entire population along the life course

Global, regional, and national comparative risk assessment of 79 behavioural, environmental and occupational, and metabolic risks or clusters of risks, 1990-2015: a systematic analysis for the Global Burden of Disease Study 2015

SummaryBackground The Global Burden of Diseases, Injuries, and Risk Factors Study 2015 provides an up-to-date synthesis of the evidence for risk factor exposure and the attributable burden of disease. By providing national and subnational assessments spanning the past 25 years, this study can inform debates on the importance of addressing risks in context. Methods We used the comparative risk assessment framework developed for previous iterations of the Global Burden of Disease Study to estimate attributable deaths, disability-adjusted life-years (DALYs), and trends in exposure by age group, sex, year, and geography for 79 behavioural, environmental and occupational, and metabolic risks or clusters of risks from 1990 to 2015. This study included 388 risk-outcome pairs that met World Cancer Research Fund-defined criteria for convincing or probable evidence. We extracted relative risk and exposure estimates from randomised controlled trials, cohorts, pooled cohorts, household surveys, census data, satellite data, and other sources. We used statistical models to pool data, adjust for bias, and incorporate covariates. We developed a metric that allows comparisons of exposure across risk factors—the summary exposure value. Using the counterfactual scenario of theoretical minimum risk level, we estimated the portion of deaths and DALYs that could be attributed to a given risk. We decomposed trends in attributable burden into contributions from population growth, population age structure, risk exposure, and risk-deleted cause-specific DALY rates. We characterised risk exposure in relation to a Socio-demographic Index (SDI). Findings Between 1990 and 2015, global exposure to unsafe sanitation, household air pollution, childhood underweight, childhood stunting, and smoking each decreased by more than 25%. Global exposure for several occupational risks, high body-mass index (BMI), and drug use increased by more than 25% over the same period. All risks jointly evaluated in 2015 accounted for 57·8% (95% CI 56·6–58·8) of global deaths and 41·2% (39·8–42·8) of DALYs. In 2015, the ten largest contributors to global DALYs among Level 3 risks were high systolic blood pressure (211·8 million [192·7 million to 231·1 million] global DALYs), smoking (148·6 million [134·2 million to 163·1 million]), high fasting plasma glucose (143·1 million [125·1 million to 163·5 million]), high BMI (120·1 million [83·8 million to 158·4 million]), childhood undernutrition (113·3 million [103·9 million to 123·4 million]), ambient particulate matter (103·1 million [90·8 million to 115·1 million]), high total cholesterol (88·7 million [74·6 million to 105·7 million]), household air pollution (85·6 million [66·7 million to 106·1 million]), alcohol use (85·0 million [77·2 million to 93·0 million]), and diets high in sodium (83·0 million [49·3 million to 127·5 million]). From 1990 to 2015, attributable DALYs declined for micronutrient deficiencies, childhood undernutrition, unsafe sanitation and water, and household air pollution; reductions in risk-deleted DALY rates rather than reductions in exposure drove these declines. Rising exposure contributed to notable increases in attributable DALYs from high BMI, high fasting plasma glucose, occupational carcinogens, and drug use. Environmental risks and childhood undernutrition declined steadily with SDI; low physical activity, high BMI, and high fasting plasma glucose increased with SDI. In 119 countries, metabolic risks, such as high BMI and fasting plasma glucose, contributed the most attributable DALYs in 2015. Regionally, smoking still ranked among the leading five risk factors for attributable DALYs in 109 countries; childhood underweight and unsafe sex remained primary drivers of early death and disability in much of sub-Saharan Africa. Interpretation Declines in some key environmental risks have contributed to declines in critical infectious diseases. Some risks appear to be invariant to SDI. Increasing risks, including high BMI, high fasting plasma glucose, drug use, and some occupational exposures, contribute to rising burden from some conditions, but also provide opportunities for intervention. Some highly preventable risks, such as smoking, remain major causes of attributable DALYs, even as exposure is declining. Public policy makers need to pay attention to the risks that are increasingly major contributors to global burden. Funding Bill & Melinda Gates Foundation

Improving the use of research evidence in guideline development: 10. Integrating values and consumer involvement

BACKGROUND: The World Health Organization (WHO), like many other organisations around the world, has recognised the need to use more rigorous processes to ensure that health care recommendations are informed by the best available research evidence. This is the 10(th )of a series of 16 reviews that have been prepared as background for advice from the WHO Advisory Committee on Health Research to WHO on how to achieve this. OBJECTIVES: We reviewed the literature on integrating values and consumers in guideline development. METHODS: We searched PubMed and three databases of methodological studies for existing systematic reviews and relevant methodological research. We reviewed the titles of all citations and retrieved abstracts and full text articles if the citations appeared relevant to the topic. We checked the reference lists of articles relevant to the questions and used snowballing as a technique to obtain additional information. We did not conduct a full systematic review ourselves. Our conclusions based on the available evidence, consideration of what WHO and other organisations are doing and logical arguments. KEY QUESTIONS AND ANSWERS: We did not find a systematic review of methods for integrating values in guidelines, but we found several systematic reviews that dealt with related topics. Whose values should WHO use when making recommendations? • Values, the relative importance or worth of a state or consequences of a decision (outcomes relating to benefits, harms, burden and costs), play a role in every recommendation. Ethical considerations, concepts that determine what is right, also play a role. • The values used in making recommendations should reflect those of the people affected. Judgements should be explicit and should be informed by input from those affected (including citizens, patients, clinicians and policy makers). • When differences in values may lead to different decisions or there is uncertainty about values, this should also be explicit. If differences in values are likely to affect a decision, such that people in different setting would likely make different choices about interventions or actions based on differences in their values, global recommendations should be explicit in terms of which values were applied and allow for adaptation after incorporating local values. How should WHO ensure that appropriate values are integrated in recommendations? • All WHO guideline groups should uniformly apply explicit, transparent and clearly described methods for integrating values. • WHO should consider involving relevant stakeholders if this is feasible and efficient. • WHO should develop a checklist for guidelines panels to help them to ensure that ethical considerations relevant to recommendations are addressed explicitly and transparently. How should users and consumers be involved in generating recommendations? • Including consumers in groups that are making global recommendations presents major challenges with respect to the impossibility of including a representative spectrum of consumers from a variety of cultures and settings. Nonetheless, consideration should be given to including consumers in groups who are able to challenge assumptions that are made about the values used for making recommendations, rather than represent the values of consumers around the world. • WHO should establish a network to facilitate involvement of users. • Draft recommendations should be reviewed by consumers, who should be asked explicitly to consider the values that were used. How should values be presented in recommendations? • Recommendations should include a description of how decisions were made about the relative importance of the consequences (benefits, harms and costs) of a decision. • Values that influence recommendations should be reported along with the research evidence underlying recommendations. • When differences in values would lead to different decisions or there is important uncertainty about values that are critical to a decision, this should be flagged and reflected in the strength of the recommendation. • Adaptable guideline templates that allow for integration of different values should be developed and used when differences in values are likely to be critical to a decision

Standards of Practice in Acute Ischemic Stroke Intervention: International Recommendations

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