Essays on Identification of Monetary Policy Shocks in Vector Autoregressive Models: Alternative Identification Schemes and Lag Structures.

This dissertation is primary concerned with the sensitivity of the effects of monetary policy shocks across alternative identification schemes and lag structures. The four widely-cited identification schemes of Christiano, Eichenbaum, and Evans (1994; 1996), Strongin (1995), Bernanke and Mihov (1998), and the long-run restrictions approach pioneered by Blanchard and Quah (1989) are used. Also, three types of lag structures---symmetric, Keating-type, and Hsiao-type asymmetric lag structures---are employed. The first essay focuses upon a closed economy framework. The results indicate that impulse response functions for macro variables are often sensitive to identification schemes and lag structures. For a given lag structure, the Strongin, Bernanke and Mihov, and long-run restrictions schemes generate similar results, while the Christiano, Eichenbaum, and Evans scheme often yields different responses from others. This essay also illustrates that the Christiano, Eichenbaum, and Evans and long-run restrictions schemes are relatively insensitive to the type of lag structures. The second essay examines the effects of lag structure misspecification within a Monte Carlo framework. It is shown that the lag structure of a VAR model does matter when assessing the effects of monetary policy shocks. For most horizons, t-statistics support for the hypothesis that the responses from the misspecified VARs are significantly different from the assumed \u27true\u27 responses. The dissertation is completed by the third essay in which the model is extended to an open economy framework. In general, the contemporaneous restriction schemes give reasonable results, but the magnitude and timing of the effects differ across identification schemes. By contrast, the long-run restrictions approach is found to be not suitable for a relatively large system like our open economy framework. Also, in this essay, the responses for the open economy are contrasted with those for the closed economy. The results indicate that the quantitative effects are different, despite the similarity in the general patterns of the responses. In particular, all identification schemes considered in this essay showed either some degree of the \u27price puzzle\u27 or weaker price effects than in a closed economy framework, even in the presence of commodity prices and the exchange rate

Application of Depth-Averaged 2D Numerical Model for Evaluation of the Vegetal Resistance in a Natural River

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

Reduced Mortality With Antiplatelet Therapy Deescalation After Percutaneous Coronary Intervention in Acute Coronary Syndromes: A Meta-Analysis

Background:Antiplatelet therapy deescalation has been suggested as an alternative to standard treatment with potent dual antiplatelet therapy (DAPT) for 1 year in low bleeding risk patients with acute coronary syndromes undergoing percutaneous coronary intervention to mitigate the increased risk of bleeding. Whether this strategy preserves the ischemic and survival benefits of potent DAPT is uncertain. Methods:We performed a pairwise meta-analysis in patients with acute coronary syndrome undergoing percutaneous coronary intervention treated with either 1-year standard potent DAPT versus deescalation therapy (potent DAPT for 1-3 months followed by either reduced potency DAPT or ticagrelor monotherapy for up to 1 year). Randomized trials comparing standard DAPT versus deescalation therapy in patients with acute coronary syndrome undergoing percutaneous coronary intervention were searched through MEDLINE, EMBASE, Cochrane databases, and proceedings of international meetings. The primary end point was 1-year all-cause mortality. Results:The meta-analysis included 6 trials in which 20 837 patients were randomized to potent DAPT for 1 to 3 months followed by deescalation therapy for up to 1 year (n=10 392) or standard potent DAPT for 1 year (n=10 445). Deescalation therapy was associated with lower 1-year rates of all-cause mortality compared with standard therapy (odds ratio, 0.75 [95% CI, 0.59-0.95]; P=0.02). Deescalation therapy was also associated with lower rates of major bleeding (odds ratio, 0.59 [95% CI, 0.48-0.72]; P<0.0001), with no significant difference in major adverse cardiac events (major adverse cardiovascular events; odds ratio, 0.89 [95% CI, 0.77-1.04]; P=0.14). Conclusions:In low bleeding risk patients with acute coronary syndrome undergoing percutaneous coronary intervention, compared with 1-year of potent DAPT, antiplatelet therapy deescalation therapy after 1 to 3 months was associated with decreased mortality and major bleeding with similar rates of major adverse cardiovascular events

Short- versus long-term dual antiplatelet therapy after drug-eluting stent implantation: An individual patient data pairwise and network meta-analysis

Background Randomized controlled trials comparing short- (≤6 months) with long-term (≥1 year) dual antiplatelet therapy (DAPT) after drug-eluting stent(s) (DES) placement have been insufficiently powered to detect significant differences in the risk of major adverse cardiac events (MACE). Objectives This study sought to compare clinical outcomes between short- (≤6 months) and long-term (1 year) DAPT and among 3 months, 6 months, and 1 year of DAPT post-DES placement by performing an individual patient data pairwise and network meta-analysis. Methods Randomized controlled trials comparing DAPT durations after DES placement were searched through the MEDLINE, EMBASE, and Cochrane databases and in international meeting proceedings. The primary study outcome was 1-year risk of MACE (cardiac death, myocardial infarction, or definite/probable stent thrombosis). Results Four trials including 8,180 randomized patients were identified. At 1-year follow-up, short-term DAPT was associated with similar rates of MACE (hazard ratio [HR]: 1.11; 95% confidence interval [CI]: 0.86 to 1.43; p = 0.44), but significantly lower rates of bleeding (HR: 0.66; 95% CI: 0.46 to 0.94; p = 0.03) versus prolonged DAPT. Comparable results were apparent in the landmark period between DAPT discontinuation and 1-year follow-up (for MACE: HR: 1.20; 95% CI: 0.77 to 1.89; p = 0.42) (for bleeding: HR: 0.44; 95% CI: 0.21 to 0.91; p = 0.03). There were no significant differences in 1-year rates of MACE among 3-month versus 1-year DAPT, 6-month versus 1-year DAPT, or 3-month versus 6-month DAPT. Conclusions Compared with prolonged DAPT, short-term DAPT is associated with similar rates of MACE but lower rates of bleeding after DES placement

Short term versus long term dual antiplatelet therapy after implantation of drug eluting stent in patients with or without diabetes: systematic review and meta-analysis of individual participant data from randomised trials.

OBJECTIVE  To compare clinical outcomes between short term (up to 6 months) and long term (12 months) dual antiplatelet therapy (DAPT) after placement of a drug eluting stent in patients with and without diabetes. DESIGN  Individual participant data meta-analysis. Cox proportional regression models stratified by trial were used to assess the impact of diabetes on outcomes. DATA SOURCE  Medline, Embase, and Cochrane databases and proceedings of international meetings searched for randomised controlled trials comparing durations of DAPT after placement of a drug eluting stent. Individual patient data pooled from six DAPT trials. PRIMARY OUTCOME  Primary study outcome was one year risk of major adverse cardiac events (MACE), defined as cardiac death, myocardial infarction, or definite/probable stent thrombosis. All analyses were conducted by intention to treat. RESULTS  Six trials including 11 473 randomised patients were pooled. Of these patients, 3681 (32.1%) had diabetes and 7708 (67.2%) did not (mean age 63.7 (SD 9.9) and 62.8 (SD 10.1), respectively), and in 84 (0.7%) the information was missing. Diabetes was an independent predictor of MACE (hazard ratio 2.30, 95% confidence interval 1.01 to 5.27; P=0.048 At one year follow-up, long term DAPT was not associated with a decreased risk of MACE compared with short term DAPT in patients with (1.05, 0.62 to 1.76; P=0.86) or without (0.97, 0.67 to 1.39; P=0.85) diabetes (P=0.33 for interaction). The risk of myocardial infarction did not differ between the two DAPT regimens (0.95, 0.58 to 1.54; P=0.82; for those with diabetes and 1.15, 0.68 to 1.94; P=0.60; for those without diabetes (P=0.84 for interaction). There was a lower risk of definite/probable stent thrombosis with long term DAPT among patients with (0.26, 0.09 to 0.80; P=0.02) than without (1.42, 0.68 to 2.98; P=0.35) diabetes, with positive interaction testing (P=0.04 for interaction), although the landmark analysis showed a trend towards benefit in both groups. Long term DAPT was associated with higher rates of major or minor bleeding, irrespective of diabetes (P=0.37 for interaction). CONCLUSIONS  Although the presence of diabetes emerged as an independent predictor of MACE after implantation of a drug eluting stent, compared with short term DAPT, long term DAPT did not reduce the risk of MACE but increased the risk of bleeding among patients with stents with and without diabetes

Three, six, or twelve months of dual antiplatelet therapy after DES implantation in patients with or without acute coronary syndromes:An individual patient data pairwise and network meta-analysis of six randomized trials and 11473 patients

AIM: We sought to determine whether the optimal dual antiplatelet therapy (DAPT) duration after drug-eluting stent (DES) placement varies according to clinical presentation. METHODS AND RESULTS: We performed an individual patient data pairwise and network meta-analysis comparing short-term (≤6-months) versus long-term (1-year) DAPT as well as 3-month vs. 6-month vs 1-year DAPT. The primary study outcome was the 1-year composite risk of myocardial infarction (MI) or definite/probable stent thrombosis (ST). Six trials were included in which DAPT after DES consisted of aspirin and clopidogrel. Among 11 473 randomized patients 6714 (58.5%) had stable CAD and 4758 (41.5%) presented with acute coronary syndrome (ACS), the majority of whom (67.0%) had unstable angina. In ACS patients, ≤6-month DAPT was associated with non-significantly higher 1-year rates of MI or ST compared with 1-year DAPT (Hazard Ratio (HR) 1.48, 95% Confidence interval (CI) 0.98-2.22; P = 0.059), whereas in stable patients rates of MI and ST were similar between the two DAPT strategies (HR 0.93, 95%CI 0.65-1.35; P = 0.71; Pinteraction = 0.09). By network meta-analysis, 3-month DAPT, but not 6-month DAPT, was associated with higher rates of MI or ST in ACS, whereas no significant differences were apparent in stable patients. Short DAPT was associated with lower rates of major bleeding compared with 1-year DAPT, irrespective of clinical presentation. All-cause mortality was not significantly different with short vs. long DAPT in both patients with stable CAD and ACS. CONCLUSIONS: Optimal DAPT duration after DES differs according to clinical presentation. In the present meta-analysis, despite the fact that most enrolled ACS patients were relatively low risk, 3-month DAPT was associated with increased ischaemic risk, whereas 3-month DAPT appeared safe in stable CAD. Prolonged DAPT increases bleeding regardless of clinical presentation. Further study is required to identify the optimal duration of DAPT after DES in individual patients based on their relative ischaemic and bleeding risks

Estimating the effects of monetary policy shocks: does lag structure matter?

This paper examines the implications of lag structure for estimating the effects of monetary policy shocks in a VAR. A symmetric lag structure in which all variables have the same lag length and an asymmetric lag structure in which the lag length differs across variables but is the same for a particular variable in each equation of the model are examined. This is important in light of the fact that the true lag structure is generally not known. Four commonly used identification schemes are employed to identify monetary policy shocks. Monte Carlo simulations strongly indicate that the lag structure of a VAR model does matter when assessing the quantitative effects of monetary policy shocks. Given the inherent uncertainty about the true lag structure in practice, it is thus important that one compare the impulse response functions from both symmetric lag and asymmetric lag VARs in assessing the effects of monetary policy shocks.