Concurrent Users Research Articles

Cloud Computing – Emerging Technology for Computational Services

The evolution of the Internet, the web development, the complexity of Internet businesses, as well as the volume of data and concurrent application users have determined IT&C specialists to design client/server applications on multiple layers, and on some cases even distributed solutions. The expansion of the Internet Service Providers networks and the accessibility of the Internet services have greatly increased the number of users that are using the Internet. This meant that new markets were opened for building new Internet businesses that rapidly grew in popularity. Because of the scaling issues generated by the large number of new users that are using Internet services, the IT&C specialists have developed solutions to share resources between companies in order to reduce operational costs. By scaling down internal resources and migrating their applications to cloud computing services, companies are cutting-down costs, increasing availability of their applications and increasing their security.

Evaluating Cramer-Rao Bound for Conformal Antenna Arrays with Directional Emitters for Doa-Estimation

Introduction. The direction-of-arrival estimation of signal sources is of serious research interest in various fields. As an example, the coordinate information in three-dimensional space can be used for spatial diversity and filtering to increase concurrent users. The influence of the directivity coefficient of a separate antenna element on the accuracy of determining the angular coordinates of radio sources of circular, cubic and spherical antenna arrays consisting of directional radiating elements that have found the widest application in modern wireless communication technologies is investigated. Theoretical results. For the correct functioning of advanced radio direction-finding algorithms along with the antenna arrays under consideration the accurate expressions describing the amplitude-phase distribution of the electromagnetic field of the arrays have been derived, so-called steering vectors. The Cramer-Rao lower bound for estimating errors and accuracy of direction-of-arrival estimation is discussed for a number planar waves arriving on an antenna array consisting of directional elements. Experimental results. A theoretical study of the operation of these antenna arrays using the Cramer-Rao lower bound was carried out, as well as computer simulations with the implementation of the MUSIC superresolution method. The influence of the directivity factor of the individual antenna element on the accuracy of the direction-of-arrival estimation of the radio emission sources by using the circular (cylindrical), cubic and spherical antenna arrays consisting of the directional antenna elements was investigated. The limits of the change of the coefficient of directional action of a separate element, at which the maximum accuracy of an estimation of angular coordinates is achieved, is determined. It is shown that further increasing the directivity factor of each antenna element makes the mean square error in the determination of the coordinates of the signals increase as well. The estimation of the resolution of conformal antenna arrays is carried out depending on the directional factor of each antenna coefficient. It is found that the best configuration is spherical. Conclusions. Thus, a comprehensive statistical analysis of radio direction finding with the azimuth and elevation for the conformal antennas depending on the directivity of the antenna elements constituting them was implemented. With an increase in the gain of individual antennas, the accuracy of direction finding can vary significantly depending on the azimuthal position of the signal and an acceptable choice of directional coefficient is four to six.

Little’s law based validation framework for load testing

Abstract Context: Performance is a key quality consideration for large-scale software systems which supports thousands of concurrent users. Load testing is an integral part of the development lifecycle and is used to address performance issues before deploying the system in production. But, how do we validate the output reported by load testing tools? Little’s Law is useful for validating the accuracy of load testing output. Though IT industry is flooded with various enterprise and open source tools for load testing, but they do not offer support for validation of its result using Little’s Law. Manual validation is time intensive and infeasible with increase in the complexity of testing scripts. Objective: In this paper we provide a Little’s law-based validation framework which will enable the researchers and industry practitioners to validate load testing results. The implementation of the framework is also demonstrated. Method: To understand the constructs commonly used in load test scripts, we analysed scripts of two open source benchmark applications and eight large-scale software systems used in industry. We found that transactions are arranged using control flow patterns like sequential, loop and conditional. Based on the analysis, we devised the framework. Results: The efficacy of the proposed framework is successfully evaluated on two systems - an open source Dell DVD Store benchmarking application and a real-world large scale system used in industry. The framework is independent of load testing tool used and can be used with complex testing scripts. Conclusions There are no known frameworks or inbuilt support in existing load testing tools for guiding practitioners on applying Little’s Law using output generated by tools. We address this significant gap by providing a framework which combines information from test scripts/reports and Little’s Law to determine whether the results are valid. The provided implementation can be easily integrated with existing load testing tools.

Hacking in the cloud

Cloud computing is a widely expanding and rapidly adopted field of technology. The ability to grant significantly more computational resources than a single machine allows, through use of virtual machines, is incredibly helpful to enterprises that need to meet the demands of hundreds of thousands of concurrent users. However, just as these resources can be used for meaningful purposes, they can also be used for malicious attacks. In this paper, we present the legal and ethical challenges of hacking in the cloud citing specific cyber laws from Canada and the United Arab Emirates, along with the terms of use of cloud service providers. We also present the results of a legal SYN (synchronization) flood attack experiment, utilizing packets with spoofed source internet protocol addresses to determine if this attack works on a cloud service provider. We offer recommendations based on whether or not the cloud platform provides sufficient utility to be used in aiding hackers with their tasks, or if the legal and ethical issues surrounding the implementations ruin any opportunities before development even begins.

Determinants of the concurrent use of biomedicine and Korean Medicine: A study based on the Korean Health Panel survey (2008–2014)

IntroductionThis study was conducted to analyze the factors associated with the concurrent use of biomedicine and Korean Medicine (KM) in an outpatient medical service using data from the Korean Health Panel (KHP) 2008–2014. MethodUsing the KHP, which is an ongoing longitudinal survey of a nationally representative Korean population, descriptive analysis was employed to present the frequency and percentage of concurrent use of biomedicine and KM with those who only used biomedicine. In addition, factors associated with the types of medical institutions receiving outpatient medical services were analyzed using the random effects panel probit model and the random effects panel logit model. ResultsAnalysis of the KHP data from 2008 to 2014 revealed that 16–18% of the population used both biomedicine and KM services concurrently. Moreover, concurrent users were more likely to be female, over 40 years old, have a lower confidence in healthcare services quality, have chronic disease, have used medication for more than three months and to have a high mean frequency of medical services use. ConclusionIdentifying determinants associated with concurrent use of biomedicine and KM might help medical professionals and policy makers to make wise judgments, plan treatments successfully and allocate resources efficiently.

Cloud rendering learning platform technology research for visual analysis of large scale 3D multimedia data

This paper designs and implements a cloud rendering system. The system supports application of server cluster load balancing, static extension of rendering machine, and design architecture of parallel task scheduling. At the same time, we put forward a new design idea, and we implement a set of communication rules of multi-task renderer and cloud rendering system. On the system, users could browse 3D scene online by mobile terminal equipments. The task of PC terminal users and mobile terminal users to access remote scenes could be high speed and real-time rendering by this system. In the end of this paper, we analyze the efficiency of our algorithm. Our system can achieve a better effect on the number of concurrent users and the average response delay. The average frame rate of system can reach 30–40 frames per second. Experimental results show that the proposed algorithm performs favorably against the state-of-the-art methods on the public test datasets.

Prevalence of drug-herb and drug-supplement interactions in older adults: a cross-sectional survey.

BackgroundPolypharmacy is common among older adults, with increasing numbers also using prescription drugs with herbal medicinal products (HMPs) and dietary supplements. There is no reliable evidence from the UK on concurrent use of HMPs and dietary supplements with prescription drugs in older adults.AimTo establish prevalence of concurrent prescription drugs, HMPs, and dietary supplements among UK community-dwelling older adults and identify potential interactions.Design and settingCross-sectional survey of older adults registered at two general practices in South East England.MethodA questionnaire asking about prescription medications, HMPs, and sociodemographic information was posted to 400 older adults aged ≥65 years, identified as taking ≥1 prescription drug.ResultsIn total 155 questionnaires were returned (response rate = 38.8%) and the prevalence of concurrent HMPs and dietary supplements with prescriptions was 33.6%. Females were more likely than males to be concurrent users (43.4% versus 22.5%; P = 0.009). The number of HMPs and dietary supplements ranged from 1 to 8, (mean = 3, median = 1; standard deviation = 1.65). The majority of concurrent users (78.0%) used dietary supplements with prescription drugs. The most commonly used dietary supplements were cod liver oil, glucosamine, multivitamins, and vitamin D. Others (20.0%) used only HMPs with prescription drugs. Common HMPs were evening primrose oil, valerian, and Nytol Herbal® (a combination of hops, gentian, and passion flower). Sixteen participants (32.6%) were at risk of potential adverse drug interactions.ConclusionGPs should routinely ask questions regarding herbal and supplement use, to identify and manage older adults at potential risk of adverse drug interactions.

Autonomic workload performance tuning in large-scale data repositories

The workload in large-scale data repositories involves concurrent users and contains homogenous and heterogeneous data. The large volume of data, dynamic behavior and versatility of large-scale data repositories is not easy to be managed by humans. This requires computational power for managing the load of current servers. Autonomic technology can support predicting the workload type; decision support system or online transaction processing can help servers to autonomously adapt to the workloads. The intelligent system could be designed by knowing the type of workload in advance and predict the performance of workload that could autonomically adapt the changing behavior of workload. Workload management involves effectively monitoring and controlling the workflow of queries in large-scale data repositories. This work presents a taxonomy through systematic analysis of workload management in large-scale data repositories with respect to autonomic computing (AC) including database management systems and data warehouses. The state-of-the-art practices in large-scale data repositories are reviewed with respect to AC for characterization, performance prediction and adaptation of workload. Current issues are highlighted at the end with future directions.

Prescription Medication Use Among Children and Adolescents in the United States.

Information on the use of prescription medications among children and adolescents in the United States is lacking. We estimate the prevalence of prescription medication use, concurrent use, and potential major drug-drug interactions (DDIs) in this population. We conducted descriptive analyses using nationally representative data for people ≤19 years old from NHANES. Data were derived from a medication log administered by direct observation during in-home interviews. Acute medications were used for ≤30 days. Concurrent use was defined as use of ≥2 prescription medications. Micromedex was used to identify potentially major DDIs. During 2013-2014, 19.8% of children and adolescents used at least 1 prescription medication, and 7.1% used acute medications. Concurrent use of prescription medications was 7.5% overall and was highest among boys 6 to 12 years old (12%) and among boys and girls ages 13 to 19 years old (10% for both). Using pooled 2009-2014 data, we found that 8.2% of concurrent users of prescription medications were at risk for a potentially major DDI. The vast majority of interacting regimens involved antidepressants and were more common among adolescent girls than boys (18.1% vs 6.6%; P < .05), driven largely by greater rates of use of acute medications. Many US children and adolescents use prescription medications with nearly 1 in 12 concurrent users of prescription medications potentially at risk for a major DDI. Efforts to prevent adverse drug events in children and adolescents should consider the role of interacting drug combinations, especially among adolescent girls.

English

Database performance throughput is one of the main measurements of the application effectiveness or a system, in terms of speed and delivery. Higher application efficiency is always a goal for any organization; therefore, finding the way to improve the database performance has priority. There are two main factors that can contribute to performance gain or slowness. Firstly, how well designed the database structure is in terms of data types, referential integrity, and indexes. Secondly, the underlying hardware infrastructure that consists of a server, storage, and network. During the application design lifecycle, the database schema is one area that continuously evolves. There are numerous configurational parameters that need to be adjusted according to database schema design and underlying infrastructure, in which in-memory is an important feature. In-memory database stores all data in physical memory, because of keeping entire data and changes of data in physical memory, the in-memory database provides very short response time and transactional throughput as compared to the disk-based database. This study provides comparison between in-memory and disk-based performance with impact analysis of concurrent users and parallelism using TPC-C benchmarking. A comprehensive benchmark guideline benefits for specific database environment was provided in order to track performance changes while migrating to in-memory from disk-based database. These benchmarking statistics provided comparative standpoint that can be verified during performance bottleneck. This study shows that transitioning from disk-based database to in-memory database decreased the response time and reduced the lock contention, however, requires detailed review for index design changes. Key words: Microsoft Structured Query Language (SQL) Server, in-memory, disk-based, transaction processing performance council (TPC-C), benchmarking, database performance, performance comparison, response time, parallelism, concurrent users.

New Opioid and Benzodiazepine Co-Prescribing and Mortality Among Veteran Affairs Patients with Posttraumatic Stress Disorder: A Retrospective Cohort Study

Objective: This study estimated the risk of all-cause mortality for patients newly prescribed opioids and benzodiazepines concurrently relative to patients prescribed benzodiazepines only, opioids only, or neither medication. Methods: This propensity score-matched, retrospective, cohort study included 17,476 patients receiving Veteran Affairs (VA) health care and diagnosed with posttraumatic stress disorder. One-year total and cause-specific mortality was assessed by hazard ratios and subhazard ratios, adjusted for propensity score, age, baseline mental health and medical comorbidity, and daily medication dose. Findings: Concurrent users (n=4,369) were propensity score matched 1:1 with benzodiazepine only, opioid only, and non-users. In the year following medication start, the concurrent cohort had higher rates of all-cause mortality (116 deaths) relative to benzodiazepine-only (75 deaths; adjusted hazard ratio=1.52, 95% CI, 1.14-2.03), opioid-only (67 deaths; 1.76, 95% CI, 1.32-2.35), and non-user (60 deaths; 1.85, 95% CI, 1.30-2.64) cohorts. Risk of overdose death was greater among patients in the concurrent cohort relative to patients in the benzodiazepine-only (adjusted subhazard ratio=2.59, 95% CI, 1.00-6.66), opioid-only (2.58, 95% CI, 1.09-6.11) and non-user (9.16, 95 CI%, 2.27-37.02) cohorts. For circulatory disease-related deaths, the adjusted subhazard ratio for concurrent medication users was 1.81 (95% CI, 1.01-3.24) relative to non-users. Interpretation: New co-prescription of opioids and benzodiazepines was associated with increased all-cause mortality and overdose death, compared with new prescription of benzodiazepines only, opioids only, or neither medication and increased circulatory disease-related death, relative to neither medication. Strategies are needed to prevent new co-prescribing and facilitate discontinuation among those co-prescribed these medication classes. Funding: Veteran Affairs Health Services Research and Development Declaration of Interest: There are no conflicts of interest to report. Ethical Approval: The study was reviewed and approved by the institutional review board of the VA Puget Sound Health Care System.

Cloudmatcher

As data science applications proliferate, more and more lay users must perform data integration (DI) tasks, which used to be done by sophisticated CS developers. Thus, it is increasingly critical that we develop hands-off DI services, which lay users can use to perform such tasks without asking for help from developers. We propose to demonstrate such a service. Specifically, we will demonstrate CloudMatcher, a hands-off cloud/crowd service for entity matching (EM). To use CloudMatcher to match two tables, a lay user only needs to upload them to the CloudMatcher's Web page then iteratively label a set of tuple pairs as match/no-match. Alternatively, the user can enlist a crowd of workers to label the pairs. In either case, the lay user can easily perform EM end-to-end without having to involve any developers. Cloud-Matcher has been used in several domain science projects at UW-Madison and at several organizations, and is scheduled to be deployed in a large company in Summer 2018. In the demonstration we will show how easy it is for lay users to perform EM (either via interactive labeling or crowdsourcing), how users can easily create and experiment with a range of EM workflows, and how CloudMatcher can scale to many concurrent users and large datasets.

Multimedia flow segmentation access mechanism with adaptive cooperative uplink and downlink

In order to improve the access efficiency of multimedia communication system and solve the problem of two-way link collaboration effectively, based on the collaboration between uplink and downlink, an adaptive multimedia streaming segmentation access mechanism is proposed. First, the multimedia communication system is divided into the transmitter division module, the receiver modular module and the relay network joint control module. In the sending end, the segmentation and flow mapping of multimedia streams are implemented. At the receiving end, the flow control of the multimedia sub-stream and the reorganization of the split flow are realized. The relay network realizes the area division and error detection of the channel capacity. Secondly, the downlink of the multimedia communication system is divided into the parallel multimedia data stream of the server cluster and multiple concurrent users. After interweaving the downlink and the uplink of the multimedia stream segmentation, the cooperative parallel multimedia stream is formed. At the same time, the interleaving weight of the downlink and the weightings of the uplink are combined in order to coordinate the area division and Realization of the channel capacity of the duplex link. Finally, simulation experiments verify the feasibility and effectiveness of the proposed algorithm in terms of resource utilization, wireless access accuracy and efficiency, and multimedia communication quality.

Comparison of Tobacco and Electronic Cigarette Reward Value Measured During a Cue-Reactivity Task: An Extension of the Choice Behavior Under Cued Conditions Procedure.

Up to 24% of electronic cigarette (e-cigarette) users are concurrent users of both tobacco and e-cigarettes (dual users). Dual users provide an opportunity to assess key motivational processes supporting e-cigarette use, such as the reward value of e-cigarettes. This study used the Choice Behavior Under Cued Conditions procedure to examine cue-specific reactions to tobacco and e-cigarettes with a primary focus on evaluating the relative reward value of both forms of cigarettes. Fifty-four dual users were exposed to a lit tobacco cigarette, their own e-cigarette, or a cup of water across multiple trials. On each trial, participants rated their craving for both tobacco and e-cigarettes and indicated the amount of money they would spend to access the cue. Key measures included craving, amount of money spent to access the cue, latency to access the cue, spending choice time, and consumption. Participants reported significantly higher craving and spent significantly more money on tobacco and e-cigarette trials than on water trials. The magnitude of cue-specific craving was comparable across tobacco and e-cigarettes, but participants spent significantly more to access tobacco cigarettes than e-cigarettes. This is the first study to demonstrate cue-specific reactivity to e-cigarettes utilizing a neutral comparison condition and to examine the reward value of e-cigarettes relative to tobacco cigarettes. Overall, the data suggest that e-cigarette puffs are less valued and generate less craving than tobacco cigarette puffs for dual users. The data provide clear support for the utility of Choice Behavior Under Cued Conditions for examining a range of motivational processes supporting e-cigarette use. The test procedure used in this research generates multiple indices of nicotine and tobacco motivation and allows for an explicit comparison of those variables in people who use both e-cigarettes and tobacco cigarettes.

Exposure-Response Association Between Concurrent Opioid and Benzodiazepine Use and Risk of Opioid-Related Overdose in Medicare Part D Beneficiaries

Concurrent benzodiazepine use is associated with an increased risk of opioid-related overdose; however, it remains unknown how the overdose risk varies with the days of exposure to both medications. To evaluate the exposure-response association between the days with concurrent prescription opioid and benzodiazepine use and the risk of overdose. Retrospective cohort study of Medicare Part D claims data from January 1, 2013, to December 31, 2014. Analyses were conducted in fall 2017 and spring 2018. Participants were Medicare Part D beneficiaries who filled at least 1 prescription for an opioid in 2014. Patients were divided into 2 groups based on whether they had opioid and benzodiazepine supplies on the day before overdose or censoring. The first group only had a supply of opioids (n = 50 583) and the second group had supplies of opioids and benzodiazepines (n = 20 665). The second group was further categorized into 4 subgroups based on the cumulative number of days with overlapping supplies of opioids and benzodiazepines: 1 to 90 days (n = 3603), 91 to 180 days (n = 2930), 181 to 270 days (n = 4082), and 271 days or more (n = 10 050). Cox proportional hazard models were constructed to compare opioid-related overdose (including fatal and nonfatal overdoses) across time-dependent treatment groups, controlling for demographic characteristics, insurance factors, clinical characteristics, and number of unique opioid and benzodiazepine prescribers. Of 71 248 total participants, 25 600 (35.9%) were male and 59 532 (83.6%) were white. Mean (SD) age was 66.5 (14.8) years. On the day before overdose or censoring event, 20 665 of 71 248 patients with an opioid prescription (29.0%) were concurrently using benzodiazepines and 14 132 of 20 665 concurrent users (68.4%) had more than 180 days of overlapping supplies of both medications. The risk of overdose was highest on the first days of concurrent opioid and benzodiazepine use and decreased over time; compared with opioid use alone, the hazard ratio for overdose was 5.05 (95% CI, 3.68-6.93) during the first 90 days of concurrent opioid and benzodiazepine use and 1.87 (95% CI, 1.25-2.80) for days 91 to 180 among those who did not have an event before 90 days. During the first 90 days, concurrent benzodiazepine use is associated with a 5-fold increase in the risk of opioid-related overdose. The implementation of policies deterring concurrent opioid and benzodiazepine use is warranted. Patients using both medications should be closely monitored, particularly during the first days of concurrent use.

Development of the Khat Knowledge, Attitudes and Perception Scale.

Khat (Catha edulis) is a stimulant plant widely used in East Africa and the Arabian Peninsula. Tobacco is often co-used with khat and its use has expanded to other parts of the world. Chronic khat use is associated with negative health consequences. There is a lack of research to develop a tool to assess attitudes toward khat use. This study aimed to develop a brief tool to assess attitude and perception related to khat (i.e. the Khat Knowledge, Attitudes and Perception Scale). Four-hundred and three participants in Yemen (151 concurrent users of khat and tobacco, 141 khat-only users and 92 non-users of khat and tobacco) were asked about knowledge and attitudes related to khat. A principle component analysis with Promax rotation, Scree-plot and Cronbach's α coefficients was performed to examine psychometric properties of the Khat Knowledge, Attitudes and Perception Scale. Principle component analysis revealed five factors: negative beliefs, positive beliefs, idleness, weight control and family issues. Internal consistency of items in negative beliefs, positive beliefs, idleness, weight control and family issues were 0.88, 0.62, 0.62, 0.72 and 0.53, respectively. Greater negative beliefs was inversely correlated with positive beliefs but positively associated with idleness, weight control and family issues. Concurrent users and khat-only users had lower scores on negative beliefs than non-users. Concurrent users had higher scores on positive beliefs than khat-only and non-users. These results provide initial support of the usefulness of the Khat Knowledge, Attitudes and Perception Scale.

LOLAweb: a containerized web server for interactive genomic locus overlap enrichment analysis.

The past few years have seen an explosion of interest in understanding the role of regulatory DNA. This interest has driven large-scale production of functional genomics data and analytical methods. One popular analysis is to test for enrichment of overlaps between a query set of genomic regions and a database of region sets. In this way, new genomic data can be easily connected to annotations from external data sources. Here, we present an interactive interface for enrichment analysis of genomic locus overlaps using a web server called LOLAweb. LOLAweb accepts a set of genomic ranges from the user and tests it for enrichment against a database of region sets. LOLAweb renders results in an R Shiny application to provide interactive visualization features, enabling users to filter, sort, and explore enrichment results dynamically. LOLAweb is built and deployed in a Linux container, making it scalable to many concurrent users on our servers and also enabling users to download and run LOLAweb locally.

A Self-Organizing Spatial Clustering Approach to Support Large-Scale Network RTK Systems.

The network real-time kinematic (RTK) technique can provide centimeter-level real time positioning solutions and play a key role in geo-spatial infrastructure. With ever-increasing popularity, network RTK systems will face issues in the support of large numbers of concurrent users. In the past, high-precision positioning services were oriented towards professionals and only supported a few concurrent users. Currently, precise positioning provides a spatial foundation for artificial intelligence (AI), and countless smart devices (autonomous cars, unmanned aerial-vehicles (UAVs), robotic equipment, etc.) require precise positioning services. Therefore, the development of approaches to support large-scale network RTK systems is urgent. In this study, we proposed a self-organizing spatial clustering (SOSC) approach which automatically clusters online users to reduce the computational load on the network RTK system server side. The experimental results indicate that both the SOSC algorithm and the grid algorithm can reduce the computational load efficiently, while the SOSC algorithm gives a more elastic and adaptive clustering solution with different datasets. The SOSC algorithm determines the cluster number and the mean distance to cluster center (MDTCC) according to the data set, while the grid approaches are all predefined. The side-effects of clustering algorithms on the user side are analyzed with real global navigation satellite system (GNSS) data sets. The experimental results indicate that 10 km can be safely used as the cluster radius threshold for the SOSC algorithm without significantly reducing the positioning precision and reliability on the user side.

Bleeding events attributable to concurrent use of warfarin and other medications in high-risk elderly: meta-analysis and Italian population-based investigation.

The aim of this study was to estimate the proportion of bleedings that occurred among warfarin users attributable to the concomitant use of other medications. A general approach for measuring the impact of the prescriptive inappropriateness on drug adverse outcomes at the population level is described. A meta-analysis was conducted to obtain summary relative risks of bleeding associated with concurrent use of warfarin and other medications compared to warfarin use alone. A population-based investigation was performed, in an Italian cohort of cardiopathic patients aged 65years or older, to estimate the prevalence of concurrent users of warfarin and other medicaments. The population attributable fraction was computed by combining data on summary relative risks and prevalence of concurrent users. Concomitant use of warfarin and cotrimoxazole, amiodarone, quinolones, macrolides, platelet aggregation inhibitors, SSRIs, NSAIDs, and lipid-lowering agents was associated with an increased risk of bleeding. The corresponding attributable fractions were 3% (95% CI 2 to 4%), 21% (1 to 41%), 21% (17 to 25%), 9% (8 to 10%), 14% (12 to 16%), 6% (5 to 8%), 10% (1 to 20%), and 8% (0 to 18%), respectively. More than half of bleeding events occurring among frail elderly using warfarin are attributable to a concomitant use of warfarin with certain drugs. Because some of these drugs appear to be essential for the treatment/prevention of cardiovascular conditions, and their concomitant use with warfarin could be acceptable in some cases, proper INR-monitoring and warfarin dose adjustments are requested.

PSY6 - Dose-Response Association Between Concurrent Opioid and Benzodiazepine use and Risk of Opioid- Related Overdose

To evaluate whether the risk of opioid-related overdose increases with the number of days with overlapping supply of opioid and benzodiazepines in a dose-response fashion. Using 2013-2014 Medicare claims data, we identified beneficiaries who filled at least one prescription for an opioid in 2014. We extracted their prescriptions for benzodiazepines in 2014 and categorized them into three groups: those who never filled prescriptions for benzodiazepines (“opioid-only users”, n=173,228), those who filled prescriptions for benzodiazepines but had no overlapping supply (“not concurrent opioid and benzodiazepine users”, n=15,022), and those with overlapping supply of opioids and benzodiazepines (“concurrent opioid and benzodiazepine users”, n=76,708). We divided the last group into 4 subgroups: those with 1-15 days of overlapping supply (n=21,795), 15-62 days (n=16,594), 62-234 days (n=19,213) and ≥235 days (n=18,493). We collected their claims for opioid-related overdose and constructed Cox proportional hazard models to compare the risk of overdose between treatment groups, controlling for demographics, insurance, clinical characteristics, and number of opioid and benzodiazepine providers. Concurrent use of opioids and benzodiazepines increased the risk of overdose in a dose-response fashion. Compared to opioid-only users, the hazard ratios (HR) for overdose were 1.55(95%CI, 1.06-2.26) for concurrent opioid and benzodiazepine users with 1-15 days of overlap, 1.71(95%CI, 1.21-2.42) for 16-62 days, 1.81(95%CI, 1.34-2.43) for 63-234 days, and 1.84(95%CI, 1.37-2.47) for ≥235 days. The risk of overdose was not significantly higher for not concurrent opioid and benzodiazepine users than for opioid-only users (HR 1.58; 95% CI, 0.99-2.51). The risk of overdose increased by 13% for each additional opioid or benzodiazepine provider. The risk of opioid-related overdose increases with the number of days with overlapping supply of opioids and benzodiazepines in a dose-response fashion. Fragmentation of care, measured as the number of opioid and benzodiazepine providers, was associated with increased risk of overdose.