Epidemiological Principles Research Articles

Modelling and stability of a synthetic drugs transmission model with relapse and treatment

In this paper, a synthetic drugs transmission model with treatment is formulated based on the principles of mathematical epidemiology. The model considers that relapse can occur among those individuals who have a history of drug abuse and we distinguish the addiction rates of susceptible individuals who have a history of drug abuse and those who have not. The global dynamics of this model are determined by the basic reproduction number, $$R_{0}$$ , under certain conditions. If $$R_{0}<1$$ , the drug-free equilibrium is globally exponentially stable for a special case and the exponential convergence rate can be unveiled, and if $$R_{0}>1$$ , the drug-addiction equilibrium is globally asymptotically stable under certain conditions. Sensitivity analysis is performed to seek for effective control measures for drug abuse. Numerical simulations are also carried out to confirm the analytical results.

Opportunity Youth: Insights and Opportunities for a Public Health Approach to Reengage Disconnected Teenagers and Young Adults.

Approximately 1 in 9 teenagers and young adults aged 16-24 in the United States is currently disconnected from school and employment. These disconnected young people (ie, opportunity youth) are not only at high risk for long-term emotional, behavioral, and health problems, but they also represent a loss of human capital, with high social and economic costs. In this article, we offer a public health perspective on opportunity youth by describing their distribution in the population and consequences of their disconnection; proposing a conceptual model of the issue based on epidemiological principles, life course development concepts, and ecological theory; and recommending multisector strategies for preventing disconnection of young people and reengaging opportunity youth. A public health approach to the problem of opportunity youth would involve developing and investing in youth monitoring data systems that can be coordinated across multiple sectors, consolidating both the delivery and funding of services for opportunity youth, developing policies and programs that encourage engagement of young people, and fostering systematic approaches to the testing and scaling up of preventive and reengagement interventions.

Epidemiology and Clinical Epidemiology

Epidemiology is a medical discipline in which the subject of study is a group of individuals who share some common feature. It is very useful to measure and quantify the level of health in populations; describe diseases; identify determinants of disease; act on the control and prevention of these; and to take action planning and evaluation health. Meanwhile, clinical epidemiology is the application of epidemiological principles and methods to problems in clinical practice; and its purpose is to promote methods of observation and interpretation that lead to valid conclusions. For the socalled father of clinical epidemiology, this is a "Science of art of medicine". Science, because it is based on knowledge, logic and previous experience that has no explanation. And art, because it is based on beliefs, judgments and intuitions without explanation. The aim of this manuscript is to summarize the differences between epidemiology and clinical epidemiology; as well as the following concepts: epidemiological object, method and epidemiological strategy.

Research Master in Population Health Management: work in progress

Background: Costs of health care are rising, we enter the era of multimorbidity and the patient experiences are more important. With the ageing of the population and increased medical and technical possibilities forecasts show that resources for health care are running out if we organise health care in the fragmented manner the way we used to. What could be a possible solution? One of the solutions is a paradigm shift from volume to value. To prepare the future health care professionals with knowledge and skills for this paradigm shift we develop a new master program course on PHM at the Leiden University Medical School Campus The Hague. We distinguish four kinds of activities in PHM that will be studied in the new master program. First: PHM can be seen as the scientific and practical endeavor to combine principles of clinical epidemiology, biostatistics and public health. Through enhanced data analysis we make predictive models for adverse outcomes. Based on individual risks on outcomes we identify subpopulations with a similar risk profile and offer proactively interventions to these subpopulations. The second part consists of choosing the right intervention. In PHM we distinguish two sets of interventions. First, interventions that address the experience of care of individuals in the population. Second, interventions that address the care gaps in relation to the best practices. Process redesign and panelmanagement are the best known interventions. The third part of PHM is on organization and governance: In order to implement this kind of health care in a population, new organizational entities request new forms of collaboration, governance and financing. The last part consists of the research methodology needed to analyse and evaluate the process and outcomes of this interdisciplinary approach. Through a combination of online education and intensive classroom weeks in the city of The Hague this master program will be eligible for graduates and post graduates from all around the world. Aims/objectives: In this workshop we would like to discuss with the participants: - The content of this new master program. - Various employment possibilities - Collaboration opportunities with other educational and research initiatives. Format: During this workshop we start with a brief introduction of about 20 minutes explaining the background and curriculum of this master program. In 2 rounds of 20 minutes, we discuss in small groups the content of this program. Participants are asked to value the various parts and come up with suggestions for the various topics. Subsequently, in 2 rounds of 20 minutes we discuss the potential collaboration with future employers the collaboration opportunities with other initiatives. Learnings: After this workshop participants have an understanding of this new master program and the collaboration possibilities for future employers and educational institutions.

Review of school vision screening guidelines

Background: Vision screenings are important in identifying visual anomalies likely to disrupt the physical, intellectual, social and emotional development of children. School health services globally include vision screenings, complementing a variety of associated screening services.Aim: This review article provides evidence for content, provision and efficacy of the vision screening services for children of school-going age and reports on the current practice of children’s vision screenings worldwide including in South Africa.Methods: Studies were identified from PubMed, Ebscohost and Science Direct with the search terms utilised during the selection of electronic articles and journals for the review. The target population includes children of school-going age from 6 to 19 years without previously known conditions associated with visual anomalies and learning-related problems. The quality of vision screening programmes and policies for the school-going age children in different countries were evaluated using Wilson and Jungner criteria.1Results: Vision screening programmes worldwide appear to support comprehensive vision screening methods among pre-schoolers (from birth to ≤ 6 years vs. children of school-going age). The development of vision screening procedures in some countries in the United States of America (USA) was found to be grounded on epidemiologic findings and principles. These may have contributed towards the formulation of national vision screening guidelines for pre-schoolers that supported the detection of amblyopia and its associated conditions such as strabismus, anisometropia and myopia. School-going children’s vision screenings are not supported worldwide as research has shown that there is lack of benefits for detecting other visual anomalies such as vergence and accommodative dysfunctions. This is despite evidence provided by the literature reviewed that an association exists between prevalent accommodation and vergence dysfunctions including poor ocular motilities and poor near-vision, among children of school-going age with poor academic performance.Conclusion: The guidelines worldwide support school vision screenings, especially for the pre-schoolers by the school health nurses, with other programs having considered the teachers, optometrists or orthoptists as the appropriate personnel to conduct the school vision screenings. There is still a need for the effectiveness of the school vision-screening programmes to be investigated related to the importance of detecting convergence and accommodative dysfunctions for the school going age children.

Planetary Epidemiology: Towards First Principles.

To combine evolutionary principles of competition and co-operation with limits to growth models, generating six principles for a new sub-discipline, called "planetary epidemiology." Suggestions are made for how to quantify four principles. Climate change is one of a suite of threats increasingly being re-discovered by health workers as a major threat to civilization. Although "planetary health" is now in vogue, neither it nor its allied sub-disciplines have, as yet, had significant impact on epidemiology. Few if any theorists have sought to develop principles for Earth system human epidemiology, in its ecological, social, and technological milieu. The principles of planetary epidemiology described here can be used to stimulate applied, quantitative work to explore past, contemporary, and future population health, at scales from local to planetary, in order to promote enduring health. It is also proposed that global well-being will decline this century, without radical reform.

GENOMOSYSTEMATICS OF RICKETTSIAE

The definition of the term genome was given by the German botanist G. Winkler almost one hundred years ago in 1920. A genome definition for bacterial (rickettsia) with a single chromosome was recently presented from the perspective of information theory, biology and bioinformatics as the information chain of nucleotides. The systematics of rickettsiae (obligate intracellular microorganisms) is based on a limited number of phenotypic characters. Classifications built on the analysis of genes, fragments of genomes and their concatenations cause discussion. Application of the Formal Order Analysis (FOA, http://foarlab.org) in the study of complete genomes allowed to submit the systematics of representatives of the family Rickettsiaceae. This approach confirmed the existence of typhus group (TG), spotted fever group (SFG), and an «ancestral» group within the genus Rickettsia, and allowed the isolation of the Rickettsia felis group within this genus, located between the «ancestral» group and the SFG and the R. akari group on the border between the SFG group and the genus Orientia. The development of the tools of FOA — «Map of Genes» and «Matrix of Similarity» — helped to conduct an in-depth study of the complete genomes of rickettsia, taking into account the characteristics of their genes and noncoding sequences. Application of these instruments, with the help of the obtained classification, confirmed the notion of ecological features of rickettsia, the structure of nosological forms and the epidemiological patterns of rickettsiosis, and made it possible to assess the virulence of the strains of the two most pathogenic species of rickettsia, R. prowazekii and R. rickettsia. In this work, for the first time, a holistic, consistent and multidimensional observation of a set of closely related bacteria (a family of bacteria) and the manifestations associated with them was carried out. The basis of the developed and herein described systematic approach to the study of bacteria is a new mathematical model — the arrangement of nucleotides in a complete genome and its sensitive unambiguous numerical characteristics. A new methodological approach named genomosystematics and based on mathematical modeling of complete genomes of rickettsiae (bacteria) using FOA. Classification of rickettsiae and rickettsioses obtained with the help of this approach corresponds to ecological, epidemiological and etiological principles. Application of the genomosystematics can serve the goals and objectives of preventive medicine. The publication completes a series of scientific works presenting the methodology of an integrated approach based on the application of mathematical analysis tools in the study of objects and laws of natural science disciplines of biological and medical profile.

Awareness of the Ward Based Outreach Team and the services offered by the programme in the Tshwane health district, South Africa

Background: The Ward Based Outreach Team (WBOT) is an organised team approach to a healthcare system based on the principles of epidemiology, primary health care, preventive medicine and health pro...

Pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma represents the most common malignant tumor of the pancreas. Despite substantial research efforts and gradual diagnostic and therapeutic improvements, its prognosis remains dismal. In accordance with the current German, European, and US guidelines, this CME-article provides acomprehensive review of the disease. In addition, selected up-to-date aspects of epidemiology, etiopathology, genetics, and basic principles of diagnostics and therapy including potential future therapeutic options are discussed.

A framework for learning about improvement: embedded implementation and evaluation design to optimize learning.

Improving health care involves many actors, often working in complex adaptive systems. Interventions tend to be multi-factorial, implementation activities diverse, and contexts dynamic and complicated. This makes improvement initiatives challenging to describe and evaluate as matching evaluation and program designs can be difficult, requiring collaboration, trust and transparency. Collaboration is required to address important epidemiological principles of bias and confounding. If this does not take place, results may lack credibility because the association between interventions implemented and outcomes achieved is obscure and attribution uncertain. Moreover, lack of clarity about what was implemented, how it was implemented, and the context in which it was implemented often lead to disappointment or outright failure of spread and scale-up efforts. The input of skilled evaluators into the design and conduct of improvement initiatives can be helpful in mitigating these potential problems. While evaluation must be rigorous, if it is too rigid necessary adaptation and learning may be compromised. This article provides a framework and guidance on how improvers and evaluators can work together to design, implement and learn about improvement interventions more effectively.

Using Epidemiological Principles to Explain Fungicide Resistance Management Tactics: Why do Mixtures Outperform Alternations?

Whether fungicide resistance management is optimized by spraying chemicals with different modes of action as a mixture (i.e., simultaneously) or in alternation (i.e., sequentially) has been studied by experimenters and modelers for decades. However, results have been inconclusive. We use previously parameterized and validated mathematical models of wheat Septoria leaf blotch and grapevine powdery mildew to test which tactic provides better resistance management, using the total yield before resistance causes disease control to become economically ineffective ("lifetime yield") to measure effectiveness. We focus on tactics involving the combination of a low-risk and a high-risk fungicide, and the case in which resistance to the high-risk chemical is complete (i.e., in which there is no partial resistance). Lifetime yield is then optimized by spraying as much low-risk fungicide as is permitted, combined with slightly more high-risk fungicide than needed for acceptable initial disease control, applying these fungicides as a mixture. That mixture rather than alternation gives better performance is invariant to model parameterization and structure, as well as the pathosystem in question. However, if comparison focuses on other metrics, e.g., lifetime yield at full label dose, either mixture or alternation can be optimal. Our work shows how epidemiological principles can explain the evolution of fungicide resistance, and also highlights a theoretical framework to address the question of whether mixture or alternation provides better resistance management. It also demonstrates that precisely how spray tactics are compared must be given careful consideration. [Formula: see text] Copyright © 2018 The Author(s). This is an open access article distributed under the CC BY 4.0 International license .

DNA Methylation as a Biomarker of Aging in Epidemiologic Studies.

Cancer is largely an aging disease. Accelerated biological aging may be the strongest predictor of cancer and other chronic disease risks. In the absence of reliable and quantifiable biomarkers of aging to date, it has long been observed that tumorigenesis shares distinct epigenetic alterations with the aging process. Recently, epigenetic age estimates have been developed based on the availability of genome-wide DNA methylation profiles, by applying in the prediction formula the methylation level at a subset of highly predictive methylation sites, called epigenetic clock. These DNA methylation age estimates have produced remarkably strong correlations with chronological age, with a small deviation and high reproducibility across different age groups and study populations. Moreover, an increasing number of epidemiologic studies have demonstrated an independent association of DNA methylation age or the extent of acceleration with mortality and various aging-related conditions, evenafter accounting for differences in chronological age and other risk factors. Although epigenetic profiles are known to be tissue-specific, both target tissue- and multiple tissue-derived estimates appear to perform well to capture what is thought to be the cumulative epigenetic drift that represents a multifactorial degenerative process across tissues and organisms. Further refinement of the epigenetic age estimates is anticipated over time to accommodate a better technological coverage of the methylome and a better understanding of the biology underlying predictive regions. Epidemiologic principles will remain critical for the evaluation of research findings involving, for example, different study populations, design, follow-up time, and quality of covariate data. Overall, the epigenetic age estimates are an exciting development with useful implications for biomedical research of healthy aging and disease prevention and control.

Conditioning on future exposure to define study cohorts can induce bias: the case of low-dose acetylsalicylic acid and risk of major bleeding.

BackgroundA principle of cohort studies is that cohort membership is defined by current rather than future exposure information. Pharmacoepidemiologic studies using existing databases are vulnerable to violation of this principle. We evaluated the impact of using data on future redemption of prescriptions to determine cohort membership, motivated by a published example seeking to emulate a “per-protocol” association between continuous versus never use of low-dose acetylsalicylic acid (ASA) and major bleeding (e.g., cerebral hemorrhage or gastrointestinal bleeding).Materials and methodsDanish medical registry data from 2004 to 2011 were used to construct two analytic cohorts. In Cohort 1, we used information about future redemption of low-dose ASA prescriptions to identify cohorts of continuous and never-ASA users. In Cohort 2, we identified ASA initiators and non-initiators using only contemporaneous data and censored follow-up for changes in use over time. We implemented propensity score-matched Poisson regression to evaluate associations between ASA use and major bleeding and estimated adjusted incidence rate differences (IRDs) per 1,000 person-years and ratios (IRRs) overall and stratified by time since initiation.ResultsAmong >6 million eligible Danish adults, we identified 403,693 low-dose ASA initiators (Cohort 2), of whom 189,150 were defined as continuous users (Cohort 1). Overall, IRDs and IRRs were similar across cohorts. However, the IRD for major bleeding in the first 90 days was substantially larger in Cohort 1 (IRD=25 per 1,000 person-years) compared with Cohort 2 (IRD=10 per 1,000 person-years).ConclusionUsing future medication redemption data to define baseline cohorts violates basic epidemiologic principles. Compared with an approach using only contemporaneous data to define cohorts, the approach based on future redemption data generated a substantially higher short-term association between low-dose ASA use and major bleeding on the absolute, but not the relative, scale possibly due to selection and immortal time biases.

Management of Endometriosis: Toward Value-Based, Cost-Effective, Affordable Care

Endometriosis management seems to be influenced by outcome-independent biomedical, pharmacological, and technological developments. The propensity towards doing more affects several aspects of care, sometimes translating into proposals that are not based on sound epidemiological principles and robust evidence. Different stakeholders share the interest for doing more testing and using novel and costly drugs or devices in patients with endometriosis. Although some women may benefit from such an approach, the majority do not, and some may be harmed. Moreover, an uncontrolled increase in expenditures for endometriosis management without demonstrated and proportional health benefits would waste the finite resources of national health care services and would risk cost-related non-adherence. Cost-effectiveness analyses should be systematically pre-planned in future trials on endometriosis, and the concept of "value" of medical interventions should guide investigators and health care policymakers. Reducing low-value care, financial toxicity, and the burden of treatment is respectful not only of endometriosis patients, but also of the entire society. Whenever possible, long-term therapeutic strategies should be tailored to each woman's needs, and high-value tests and treatments should be chosen based on her priorities and preferences. Moreover, listening to patients, understanding their concerns, avoiding disease labelling, explaining plainly what is known and what is unknown, and giving constant reassurance and encouragement may be exceedingly important for the successful management of endometriosis and may change the patient's perception of her clinical condition. Physician empathy has no untoward effects, does not cause harms, and may determine whether a woman successfully copes or desperately struggles with her disease during reproductive life.

An attempt to replace an ivermectin-resistant Cooperia spp. population by a susceptible one on grazing pastures based on epidemiological principles and refugia management

The maintenance of anthelmintic-susceptible parasite refugia to delay the onset of anthelmintic resistance is an almost impossible effort in many grazing livestock production countries given that current refugia consist of already resistant parasites. Rather, efforts could be focused on replacing the resistant parasite refugia by susceptible parasite ones and implementing sustainable parasite control measures from then on. To this purpose, a trial was conducted to attempt to establish a new population of ivermectin-susceptible Cooperia sp. on a beef cattle farm with proven problems of ivermectin-resistant Cooperia. During two consecutive years, 82 (Year 1) and 100 (Year 2) recently weaned and parasite-free heifers were inoculated with 40,000 or 30,000 susceptible Cooperia L3, respectively, at a time when levels of resistant parasite refugia were normally low. The animals were subsequently allowed to graze on the problem pastures during autumn until the end of spring. Levels of parasitism in the animals and on pasture were monitored monthly and animals were treated with levamisole when needed. The combination of parasitological monitoring and local epidemiological knowledge was essential to determine when treatments were to be administered. No clinical signs of gastrointestinal parasitosis in the herd were observed throughout the study and unnecessary treatments were avoided. Faecal egg counts reduction tests (FECRT) and controlled efficacy tests (CET) employing worm counts were carried out at different times throughout the study to determine the clinical efficacy (FECRT) and the absolute efficacy (CET) of ivermectin, respectively. The clinical efficacy of ivermectin increased from an initial 73% to 99.4%, while the absolute efficacy increased from 54.1% to 87.5% after just two animal production cycles. The switch from a resistant parasite population to a susceptible one requires knowledge of parasitological epidemiology, especially in relation to seasonal variations of parasite populations in both the host and in refugia.

Introduction: Biostatistics and epidemiology lecture series, part 1.

Physicians are inundated with clinical research findings that potentially impact patient care. Evaluating the strength and clinical application of research results requires an understanding of the underlying biostatistics and epidemiological principles. The articles in this supplement are based on

Basic principles of test-negative design in evaluating influenza vaccine effectiveness.

Based on the unique characteristics of influenza, the concept of "monitoring" influenza vaccine effectiveness (VE) across the seasons using the same observational study design has been developed. In recent years, there has been a growing number of influenza VE reports using the test-negative design, which can minimize both misclassification of diseases and confounding by health care-seeking behavior. Although the test-negative designs offer considerable advantages, there are some concerns that widespread use of the test-negative design without knowledge of the basic principles of epidemiology could produce invalid findings. In this article, we briefly review the basic concepts of the test-negative design with respect to classic study design such as cohort studies or case-control studies. We also mention selection bias, which may be of concern in some countries where rapid diagnostic testing is frequently used in routine clinical practices, as in Japan.

Comparative Analysis of Mortality from Infectious Diseases in the Russian Federation and Some European Countries

The purpose. To conduct comparative evaluation of mortality from infectious diseases and medical care quality in Russia and some European countries in different age groups. Materials and methods. Selection of mortality data was performed from various Russian and foreign databases. Ranking of countries according to mortality rates was done with a quartiles calculation method. For evaluating the adherence to preventive measures surveys of different population groups, to assess adherence to the principles of clinical epidemiology and evidence-based medicine was conducted a continuous survey of doctors, one branch of the municipal polyclinic of Moscow. The results and discussion. It is shown that the situation in the Russian Federation as a whole can be assessed as disadvantaged in mortality from infectious diseases in all age groups. Conclusions. A reduction in mortality among children as well as working-age population requires a comprehensive approach that should include both of improvement of quality of care and the formation of commitment to preventive measures.

The management of traumatic brain injury

Abstract Paediatric head injury is an important clinical problem. Essential management begins with initial resuscitation supporting the airway, breathing and circulatory systems with cervical spine stabilization. Neurological assessment should include evaluation of the Glasgow Coma Score and pupil reactivity. Further imaging, admission for observation and neurosurgical referral may be indicated. This article is aimed at the general paediatrician and emergency department physician. We discuss the epidemiology, pathophysiology and general principles of paediatric head injury management from the time of injury through to discharge from hospital.

Should Controls With Respiratory Symptoms Be Excluded From Case-Control Studies of Pneumonia Etiology? Reflections From the PERCH Study.

Many pneumonia etiology case-control studies exclude controls with respiratory illness from enrollment or analyses. Herein we argue that selecting controls regardless of respiratory symptoms provides the least biased estimates of pneumonia etiology. We review 3 reasons investigators may choose to exclude controls with respiratory symptoms in light of epidemiologic principles of control selection and present data from the Pneumonia Etiology Research for Child Health (PERCH) study where relevant to assess their validity. We conclude that exclusion of controls with respiratory symptoms will result in biased estimates of etiology. Randomly selected community controls, with or without respiratory symptoms, as long as they do not meet the criteria for case-defining pneumonia, are most representative of the general population from which cases arose and the least subject to selection bias.