A general framework for statistical performance comparison of evolutionary computation algorithms

This paper proposes a statistical methodology for comparing the performance of evolutionary computation algorithms. A two-fold sampling scheme for collecting performance data is introduced, and this data is assessed using a multiple hypothesis testing framework relying on a bootstrap resampling procedure. The proposed method offers a convenient, flexible, and reliable approach to comparing algorithms in a wide variety of applications. KEY WORDS Evolutionary computation, statistics, performanc

An Enhanced Bat Algorithm for Parallel Localization Based on a Mobile Beacon Sensor in Wireless Sensor Networks

International audienceWireless sensor networks (WSNs) have done extensive work over the past decade, focusing primarily on node position in large WSNs when using Internet of Things. When a few anchor nodes are established, the location of sensor nodes must be found and defined in a large network. The goal is to solve this problem by means of an energy-minimal and high-precision protocol. We suggest an improved parallel position scheme based on Bat algorithms, in this article. The main idea is to use a mobile node in the middle of certain network nodes. Wherein, the center node moves along a spiral path to locate its neighboring nodes in parallel. Simulation results of some case studies show remarkable localization quality with regard to accuracy and energy consumption

Use of Medications for Secondary Prevention After Coronary Bypass Surgery Compared With Percutaneous Coronary Intervention

ObjectivesThis study sought to compare use of evidence-based secondary preventive medications after coronary bypass surgery (CABG) and percutaneous coronary intervention (PCI).BackgroundUse of cardioprotective medication after coronary revascularization has been inconsistent and relatively low in older studies.MethodsWe studied patients in a large integrated healthcare delivery system who underwent CABG or PCI for new onset coronary disease. We used data from health plan databases about prescriptions dispensed during the first year after initial coronary revascularization to identify patients who never filled a prescription and to calculate the medication possession ratio among patients who filled at least 1 prescription. We focused on angiotensin-converting enzyme inhibitors (ACEI), angiotensin receptor blockers (ARBs), beta-blockers, and statins.ResultsBetween 2000 and 2007, 8,837 patients with new onset coronary disease underwent initial CABG, and 14,516 underwent initial PCI. Patients receiving CABG were more likely than patients receiving PCI to not fill a prescription for a statin (7.1% vs. 4.8%, p < 0.0001) or for an ACEI/ARB (29.1% vs. 22.4%, p < 0.0001), but similar proportions never filled a prescription for a beta-blocker (6.4% vs. 6.1%). Among those who filled at least 1 prescription post-revascularization, patients receiving CABG had lower medication possession ratios than patients receiving PCI for ACEI/ARBs (69.4% vs. 77.8%, p < 0.0001), beta-blockers (76.1% vs. 80.6%, p < 0.0001), and statins (82.7% vs. 84.2%, p < 0.001).ConclusionsPatients who received CABG were generally less likely than patients who received PCI to fill prescriptions for secondary preventive medications and to use those medications consistently in the first year after the procedure

Abstract 253: Comparative Effectiveness of Clopidogrel in Medically Managed Patients with Unstable Angina and non-ST Segment Myocardial Infarction

Background: The CURE trial demonstrated improved outcomes with the addition of clopidogrel to aspirin in unstable angina (UA) or NSTEMI, leading to guideline adoption and widespread use. Although the role of clopidogrel after PCI is well studied, 40-50% of patients with UA/NSTEMI are medically managed, i.e., without revascularization during the index hospitalization. The effectiveness and optimal duration in real-world medically managed patients is unknown. Methods: We conducted a retrospective cohort study of all adult members of Kaiser Permanente of Northern California, a large, integrated health care delivery system, without known CAD or prior clopidogrel use who presented with UA/NSTEMI from 2003-2008 and did not receive revascularization (PCI or CABG) during the index hospitalization or within 7 days post-discharge (i.e., “medically managed”). We measured the association between use of clopidogrel within 7 days of discharge with subsequent all-cause mortality and MI at 2 years of follow up. Outcomes were examined in unmatched and propensity-matched multivariable Cox regression analyses, adjusted for demographics, comorbidities, longitudinal medication use and secular trends. Results: We identified 18,771 patients (mean age 69.3 years; 42.4% women) with incident UA (34.7%) or NSTEMI (65.3%) followed for a mean 2.5 years after the initial event. Clopidogrel prescription within 7 days of discharge was observed for 34.5% of the sample. Among these, the mean duration of continuous clopidogrel use was 255 days. An additional 1.6% filled a clopidogrel prescription between 7 and 30 days after discharge, and 5.0% filled a prescription after 30 days. During the first 2-years of follow up, patients prescribed clopidogrel within the first 7 days after discharge had lower unadjusted rates of all-cause mortality (7.5% vs 19.2%, p &lt; 0.001; HR = 0.42, 95% CI [0.38-0.45]) and subsequent MI (6.5% vs 8.2%, p = 0.002; HR = 0.85 [0.76-0.95]). In multivariable Cox regression models, clopidogrel users had lower risk of 2-year all-cause mortality (HR = 0.65, [0.60-0.71]) but similar rates of MI (HR = 1.07, [0.96-1.20]). Propensity-matched models demonstrated similar results. A sensitivity analysis in which clopidogrel use was defined by initiation within 30-days post-discharge also demonstrated similar results. Conclusions: In a large community-based sample of patients with incident medically managed UA/NSTEMI, receipt of early post-discharge clopidogrel was independently associated with lower rates of death but similar rates of MI. Future research should identify the subset of patients who experience the greatest net clinical benefit with clopidogrel after UA/NSTEMI as well as the optimal duration of treatment. </jats:p

Beta-Blocker Therapy and Cardiac Events Among Patients With Newly Diagnosed Coronary Heart Disease

AbstractBackgroundThe effectiveness of beta-blockers for preventing cardiac events has been questioned for patients who have coronary heart disease (CHD) without a prior myocardial infarction (MI).ObjectivesThe purpose of this study was to assess the association of beta-blockers with outcomes among patients with new-onset CHD.MethodsWe studied consecutive patients discharged after the first CHD event (acute coronary syndrome or coronary revascularization) between 2000 and 2008 in an integrated healthcare delivery system who did not use beta-blockers in the year before entry. We used time-varying Cox regression models to determine the hazard ratio (HR) associated with beta-blocker treatment and used treatment-by-covariate interaction tests (pint) to determine whether the association differed for patients with or without a recent MI.ResultsA total of 26,793 patients were included, 19,843 of whom initiated beta-blocker treatment within 7 days of discharge from their initial CHD event. Over an average of 3.7 years of follow-up, 6,968 patients had an MI or died. Use of beta-blockers was associated with an adjusted HR for mortality of 0.90 (95% confidence limits [CL]: 0.84 to 0.96), and an adjusted HR for death or MI of 0.92 (CL: 0.87 to 0.97). The association between beta-blockers and outcomes differed significantly between patients with and without a recent MI (HR for death: 0.85 vs. 1.02, pint = 0.007; and HR for death or MI: 0.87 vs. 1.03, pint = 0.005).ConclusionsUse of beta-blockers among patients with new-onset CHD was associated with a lower risk of cardiac events only among patients with a recent MI