CLARIFYING (OPPORTUNITY) COSTS Stone, Daniel F.
The American Economist (New York, N.Y. 1960),
03/2015, Letnik:
60, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Opportunity cost is widely considered to be a fundamental concept in economics. But the definition of the term continues to be both unclear and controversial. I describe how the term is widely used ...in two distinct ways, both in academic and non-academic contexts. I propose a practical way for educators to clarify the concept and related terminology.
Aim
To evaluate the impact of left ventricular ejection fraction (LVEF) on 3‐year outcomes in patients with left main coronary artery disease (LMCAD) undergoing percutaneous coronary intervention ...(PCI) or coronary artery bypass grafting (CABG) in the EXCEL trial.
Methods and results
The EXCEL trial randomized patients with LMCAD to PCI with everolimus‐eluting stents (n = 948) or CABG (n = 957). Among 1804 patients with known baseline LVEF, 74 (4.1%) had LVEF <40% heart failure with reduced ejection fraction (HFrEF), 152 (8.4%) LVEF 40–49% heart failure with mid‐range ejection fraction (HFmrEF) and 1578 (87.5%) LVEF ≥50% (heart failure with preserved ejection fraction). Patients with HFrEF vs. HFmrEF vs. preserved LVEF experienced a longer postoperative hospital stay (9.0 vs. 7.0 vs. 6.0 days, P = 0.02) with greater peri‐procedural complications after CABG, while hospital stay after PCI was unaffected by LVEF (1.5 vs. 2.0 vs. 1.0 days, P = 0.20). The composite primary endpoint of death, stroke, or myocardial infarction at 3 years was 29.3% (PCI) vs. 27.6% (CABG) in patients with HFrEF, 16.2% vs. 15.0% in patients with HFmrEF, and 14.5% vs. 14.6% in those with preserved LVEF, respectively (Pinteraction = 0.90). Smoothing spline analysis demonstrated that the 3‐year risk of all‐cause death increased when LVEF decreased, both in patients undergoing CABG and PCI.
Conclusion
In the EXCEL trial, the composite rate of death, stroke or myocardial infarction at 3 years was significantly higher in patients with HFrEF compared with HFmrEF or preserved LVEF, driven by an increased rate of all‐cause death. No significant differences after PCI vs. CABG were observed among patients with HFrEF, HFmrEF and preserved LVEF. Longer‐term follow‐up could provide important insights on differences in clinical outcomes that might emerge over time.
Clinical Trial Registration:
ClinicalTrials.gov Identifier NCT01205776.
Objectives
To assess the in vitro activity of ceftazidime/avibactam against a recent, 2015–18, collection of clinical isolates of Gram-negative bacilli from Middle Eastern and African countries with ...a focus on isolates from ICUs and with MDR and difficult-to-treat resistance (DTR) phenotypes.
Methods
Antimicrobial susceptibility testing of 4608 isolates of Enterobacterales (997 isolates from ICU patients) and 1358 isolates of Pseudomonas aeruginosa (374 isolates from ICU patients) was performed by CLSI broth microdilution methodology in a central laboratory. MICs were interpreted using both CLSI (2020) and EUCAST (2020) MIC breakpoints.
Results
Most isolates of Enterobacterales (Middle East: ICU, 99.1% susceptible, non-ICU, 99.1%; Africa: ICU, 96.9% susceptible, non-ICU, 98.3%) and P. aeruginosa (Middle East: ICU, 93.4%, non-ICU, 92.1%; Africa: ICU, 89.8%; non-ICU, 94.1%) were susceptible to ceftazidime/avibactam. Applying CLSI and EUCAST breakpoints, MDR rates were similar for Enterobacterales (27.8%–36.0% of isolates) and P. aeruginosa (25.0%–36.4%) while DTR rates were lower for Enterobacterales (1.6%–1.8%) than for P. aeruginosa (5.2%–7.4%). Percentage susceptible rates for ceftazidime/avibactam for MDR Enterobacterales were 96.8%–97.5% (Middle East) and 92.5%–94.3% (Africa) while rates for P. aeruginosa were 70.1%–80.0% (Middle East) and 69.5%–78.2% (Africa). 60.5%–65.8% (Middle East) and 38.9%–52.2% (Africa) of isolates of Enterobacterales with DTR phenotypes were ceftazidime/avibactam susceptible as were 29.2%–31.1% (Middle East) and 28.2%–35.8% (Africa) of DTR P. aeruginosa.
Conclusions
Overall, the isolates of Enterobacterales and P. aeruginosa tested from Middle Eastern and African countries were highly susceptible to ceftazidime/avibactam. Most MDR and many DTR isolates of Enterobacterales and P. aeruginosa were susceptible to ceftazidime/avibactam.
Pope and Schweitzer (2011) study predictions of prospect theory for the reference point of par on the current hole in professional golf. We study prospect-theory predictions of three other plausible ...reference points: par for recent holes, for the round, and for the tournament. A potentially competing force is momentum in quality of play, that is, the hot or cold hand. While prospect theory predicts negative serial correlation in better (worse)-than-average performance across holes, the hot (cold) hand implies the opposite. We find evidence that, for each of the reference points we study, when scores are better than par, hot-hand effects are dominated by prospect-theory effects. These effects can occur via two mechanisms: greater conservatism or less effort. We find evidence that the former (latter) dominates for scores closer to (further from) the reference point. We also find evidence of prospect theory effects (greater risk seeking) when scores are worse than par for the round in Round 1 and of cold-hand effects for scores worse than par for the tournament in Round 3. The magnitudes of some of the joint effects are comparable to those found by Pope and Schweitzer and other related papers. We conclude by discussing how, rather than compete, prospect-theory and cold-hand forces might also cause one another.
This article analyzes a simple model of policy making under uncertainty in the presence of an interest group that may fund and lobby research. In the model, if research is not disclosed via lobbying ...it enters the public domain and, subsequently, is randomly observed by the policy maker (PM). Consequently, the interest group strategically chooses both whether to fund research and whether to lobby it versus let it be randomly observed. The main result is that for a range of parameter values, in equilibrium the interest group sometimes funds, but never lobbies, research. This behavior effectively "jams" the public signal of the PM, making the policy choice worse on average. This occurs despite all research being unbiased. The results provide qualified theoretical support for the value of research funding transparency and implications for the interpretation of interest group funded research.
U.S. college football’s traditional bowl system, and lack of a postseason play-off tournament, has been controversial for years. The conventional wisdom is that a play-off would be a more fair way to ...determine the national champion, and more fun for fans to watch. The colleges finally agreed to begin a play-off in the 2014-2015 season, but with just four teams, and speculation continues that more teams will be added soon. A subtle downside to adding play-off teams is that it reduces the significance of regular season games. We use the framework of Ely, Frankel, and Kamenica (in press) to directly estimate the utility fans would get from this significance, that is, utility from suspense, under a range of play-off scenarios. Our results consistently indicate that play-off expansion causes a loss in regular season suspense utility greater than the gain in the postseason, implying the traditional bowl system (two team play-off) is suspense-optimal. We analyze and discuss implications for TV viewership and other contexts.
Mammographic density, the area of the mammographic image that appears white or bright, predicts breast cancer risk. We estimated the proportions of variance explained by questionnaire-measured breast ...cancer risk factors and by unmeasured residual familial factors.
For 544 MZ and 339 DZ twin pairs and 1,558 non-twin sisters from 1,564 families, mammographic density was measured using the computer-assisted method Cumulus. We estimated associations using multilevel mixed-effects linear regression and studied familial aspects using a multivariate normal model.
The proportions of variance explained by age, body mass index (BMI), and other risk factors, respectively, were 4%, 1%, and 4% for dense area; 7%, 14%, and 4% for percent dense area; and 7%, 40%, and 1% for nondense area. Associations with dense area and percent dense area were in opposite directions than for nondense area. After adjusting for measured factors, the correlations of dense area with percent dense area and nondense area were 0.84 and -0.46, respectively. The MZ, DZ, and sister pair correlations were 0.59, 0.28, and 0.29 for dense area; 0.57, 0.30, and 0.28 for percent dense area; and 0.56, 0.27, and 0.28 for nondense area (SE = 0.02, 0.04, and 0.03, respectively).
Under the classic twin model, 50% to 60% (SE = 5%) of the variance of mammographic density measures that predict breast cancer risk are due to undiscovered genetic factors, and the remainder to as yet unknown individual-specific, nongenetic factors.
Much remains to be learnt about the genetic and environmental determinants of mammographic density.
The aim of the present study is to determine if body mass index (BMI) during childhood is associated with the breast cancer risk factor ‘adult mammographic density adjusted for age and BMI’. In 1968, ...the Tasmanian Longitudinal Health Study studied every Tasmanian school child born in 1961. We obtained measured heights and weights from annual school medical records across ages 7–15 years and imputed missing values. Between 2009 and 2012, we administered to 490 women a questionnaire that asked current height and weight and digitised at least one mammogram per woman. Absolute and percent mammographic densities were measured using the computer-assisted method CUMULUS. We used linear regression and adjusted for age at interview and log current BMI. The mammographic density measures were negatively associated: with log BMI at each age from 7 to 15 years (all
p
< 0.05); with the average of standardised log BMIs across ages 7–15 years (
p
< 0.0005); and more strongly with standardised log BMI measures closer to age 15 years (
p
<
0.03). Childhood BMI measures explained 7 and 10 % of the variance in absolute and percent mammographic densities, respectively, and 25 and 20 % of the association between current BMI and absolute and percent mammographic densities, respectively. Associations were not altered by adjustment for age at menarche. There is a negative association between BMI in late childhood and the adult mammographic density measures that predict breast cancer risk. This could explain, at least in part, why BMI in adolescence is negatively associated with breast cancer risk.
Abstract
Background
We applied machine learning to find a novel breast cancer predictor based on information in a mammogram.
Methods
Using image-processing techniques, we automatically processed ...46 158 analog mammograms for 1345 cases and 4235 controls from a cohort and case–control study of Australian women, and a cohort study of Japanese American women, extracting 20 textural features not based on pixel brightness threshold. We used Bayesian lasso regression to create individual- and mammogram-specific measures of breast cancer risk, Cirrus. We trained and tested measures across studies. We fitted Cirrus with conventional mammographic density measures using logistic regression, and computed odds ratios (OR) per standard deviation adjusted for age and body mass index.
Results
Combining studies, almost all textural features were associated with case–control status. The ORs for Cirrus measures trained on one study and tested on another study ranged from 1.56 to 1.78 (all P < 10−6). For the Cirrus measure derived from combining studies, the OR was 1.90 (95% confidence interval CI = 1.73 to 2.09), equivalent to a fourfold interquartile risk ratio, and was little attenuated after adjusting for conventional measures. In contrast, the OR for the conventional measure was 1.34 (95% CI = 1.25 to 1.43), and after adjusting for Cirrus it became 1.16 (95% CI = 1.08 to 1.24; P = 4 × 10−5).
Conclusions
A fully automated personal risk measure created from combining textural image features performs better at predicting breast cancer risk than conventional mammographic density risk measures, capturing half the risk-predicting ability of the latter measures. In terms of differentiating affected and unaffected women on a population basis, Cirrus could be one of the strongest known risk factors for breast cancer.
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