The predictive capacity of a marker in a population can be described using the population distribution of risk (Huang et al. 2007; Pepe et al. 2008a; Stern 2008). Virtually all standard statistical summaries of predictability and discrimination can be derived from it (Gail and Pfeiffer 2005). The goal of this paper is to develop methods for making inference about risk prediction markers using summary measures derived from the risk distribution. We describe some new clinically motivated summary measures and give new interpretations to some existing statistical measures. Methods for estimating these summary measures are described along with distribution theory that facilitates construction of confidence intervals from data. We show how markers and, more generally, how risk prediction models, can be compared using clinically relevant measures of predictability. The methods are illustrated by application to markers of lung function and nutritional status for predicting subsequent onset of major pulmonary infection in children suffering from cystic fibrosis. Simulation studies show that methods for inference are valid for use in practice.
Using historical census and survey data, Long and Ferrie (forthcoming) found a significant decline in social mobility in the United States from 1880 to 1973. We present two critiques of the Long-Ferrie study. First, the data quality of the Long-Ferrie study is more limiting than the authors acknowledge. Second, and more critically, they applied a method ill-suited for measuring social mobility of farmers in a comparative study between 1880 and 1973, a period in which the proportion of farmers dramatically declined in the U.S. We show that Long and Ferrie’s main conclusion is all driven by this misleading result for farmers.
Social mobility; U.S. history; Census data
Cohabitation has become the modal path to marriage in the United States. However, little is known about what cohabitation means to young adults today. Drawing on data from 18 focus groups (N=138) and 54 in-depth interviews with young adults, this exploratory study investigates motivations to cohabit, and examines potential gender differences in those motivations and the meanings attached to them. We find that primary motives to cohabit include spending time together, sharing expenses, and evaluating compatibility. Strong gender differences emerge in how respondents discuss these themes and how they characterize the drawbacks of cohabitation, with men more concerned about loss of freedom and women with delays in marriage. Overall, our findings suggest that gendered cultural norms governing intimate relationships extend to cohabiting unions, and point to gender differences in the perceived role of cohabitation in union formation processes.
cohabitation; gender; union formation; marriage
Pragmatic differentiation in bilinguals is the ability to use two languages appropriately with different speakers. Although some sensitivity emerges by 2 years, the effect of context on these skills and their relation to other developing metacognitive capacities have not been examined. The current study compared the language use of 28 bilingual children (2;7 to 3;10 and 4;1 to 4;11) across two tasks. All children were bilingual in English and Marathi, an Indian language. Theory-of-mind measures were included to assess whether developing cognitive capacities relate to pragmatic language ability. Results indicated that pragmatic differentiation is not an all-or-none ability, but one which develops over the preschool years and varies based on the conversational context. This development is also related to metacognitive abilities which emerge during this time.
There are large amounts of unstructured, free-text information about quality of health care available on the Internet in blogs, social networks, and on physician rating websites that are not captured in a systematic way. New analytical techniques, such as sentiment analysis, may allow us to understand and use this information more effectively to improve the quality of health care.
We attempted to use machine learning to understand patients’ unstructured comments about their care. We used sentiment analysis techniques to categorize online free-text comments by patients as either positive or negative descriptions of their health care. We tried to automatically predict whether a patient would recommend a hospital, whether the hospital was clean, and whether they were treated with dignity from their free-text description, compared to the patient’s own quantitative rating of their care.
We applied machine learning techniques to all 6412 online comments about hospitals on the English National Health Service website in 2010 using Weka data-mining software. We also compared the results obtained from sentiment analysis with the paper-based national inpatient survey results at the hospital level using Spearman rank correlation for all 161 acute adult hospital trusts in England.
There was 81%, 84%, and 89% agreement between quantitative ratings of care and those derived from free-text comments using sentiment analysis for cleanliness, being treated with dignity, and overall recommendation of hospital respectively (kappa scores: .40–.74, P<.001 for all). We observed mild to moderate associations between our machine learning predictions and responses to the large patient survey for the three categories examined (Spearman rho 0.37-0.51, P<.001 for all).
The prediction accuracy that we have achieved using this machine learning process suggests that we are able to predict, from free-text, a reasonably accurate assessment of patients’ opinion about different performance aspects of a hospital and that these machine learning predictions are associated with results of more conventional surveys.
Internet; patient experience; quality; machine learning
An issue of increasing interest in Pavlovian conditioning is to identify ways to facilitate the development and persistence of extinction. Both behavioral and molecular lines of evidence demonstrate that learning during extinction can be enhanced. Similar evidence has been offered to support the idea that extinction causes the original association to be unlearned, or erased. Differentiating between extinction and erasure accounts is extremely difficult and requires many assumptions about the fundamental nature of how memory storage maps into memory expression. In this issue of Behavioral Neuroscience, Norrholm, et al (2008) describe a study of extinction with humans that has the potential to serve as a translational bridge between rodent work and clinical applications. They find less recovery of a conditioned fear response when extinction occurs 10-min compared to 72-hr after conditioning; however, the recovery of subjects’ expectancies of the fearful stimulus is independent of when extinction occurred. These findings and others discussed here demonstrate some of the challenges in making inferences about memory erasure during extinction.
Extinction; consolidation; reconsolidation; memory storage; memory erasure
The National Poisons Information Services (NPIS) covering the United Kingdom and the Republic of Ireland currently receive over 40,000 telephone inquiries a year. Over the years there has been little change in the proportion of inquiries related to each of the main categories of poisons (drugs, household, chemical, agricultural, animals, and plants). More detailed analysis, however, shows pronounced changes in the inquiries relating to specific types of poisoning, particularly with drugs. By monitoring these trends and assessing the risks of toxicity, the NPIS has an important role in informing the medical profession of the need for preventive measures and for improved methods of treatment. At present, the NPIS cannot make full use of the available data due to inadequate staffing and lack of computer facilities. It is argued that for a modest increase in funding a much more comprehensive service could be provided.
The Commission's Green Paper on Bio–preparedness represents an important signal that the European Commission is actively involved in, working on issues related to bio–preparedness across all Member States and the international Community. In 2006, the Commission held two seminars on European Bio Preparedness and a workshop on Transport and Traceability of Bio materials. The results and recommendations emerging from these discussions have been inserted in this Green Paper. The document intends to stimulate a debate within and between the Member States and to launch a process of consultation on how to reduce biological risks and to enhance preparedness and response. All the national authorities responsible for risk prevention and response, human, animal and plant health, customs, civil protection, law enforcement authorities, the military, bio–industry, epidemiological and health communities, academic institutions and bioresearch institutes are therefore called to be involved, to contribute and to improve the ability of the EU to prevent, respond to and recover from a biological incident or deliberate criminal activity.
This analysis joins the debate on how declines in marriage have shifted the composition of the unmarried and married populations in the United States, and how compositional shifts have affected nonmarital birth rates. Gray, Stockard, and Stone (2006) presented one model for compositional effects that Ermisch (2009) challenged with alternative statistical tests. I propose an alternative model for compositional shifts based not on theory but on observed marriage and fertility patterns. The results from this alternative model are consistent with Ermisch’s findings yet support Gray et al.’s general case that compositional effects have had an important influence on nonmarital birth rates.
Objectives To study the reasons given by junior doctors trained in the United Kingdom for considering leaving UK medicine.
Design Analysis of replies to postal questionnaire surveys.
Setting United Kingdom.
Participants 1326 doctors who qualified in 1999.
Main outcome measure Reasons for considering leaving.
Results Of 1047 doctors who indicated that they would stay in medicine but not necessarily in the United Kingdom, 65% (682) gave reasons for leaving that concerned lifestyle, such as a preference for living outside the United Kingdom; 41% (433) gave reasons concerning working conditions in UK medicine; and 18% (184) gave positive work related reasons, such as wanting to work in developing countries. Of 279 doctors considering leaving medicine, 75% (210) cited working conditions, 23% (63) cited lifestyle reasons, and 9% (24) cited positive interests in a different career. Of the 169 doctors who said that they would probably or definitely leave the United Kingdom but remain in medicine, 78% (132) specified lifestyle reasons. Of the 42 who said that they would probably or definitely leave medicine, 67% (28) cited working conditions.
Conclusions The wish to work abroad, but to stay in medicine, was more common than the wish to leave medicine. The preference for a different lifestyle, particularly to live outside the United Kingdom, is not readily amenable to policy changes to the medical working environment. The smaller numbers of doctors who gave work experience as a reason for considering leaving medicine might be influenced to stay by improvements in working lives.
During the 2009 H1N1 pandemic, a vaccine was made available to all Canadians. Despite efforts to promote vaccination, the public's intent to vaccinate remained low. In order to better understand the public's resistance to getting vaccinated, this study addressed factors that influenced the public's decision making about uptake. To do this, we used a relatively novel source of qualitative data – comments posted on-line in response to news articles on a particular topic. This study analysed 1,796 comments posted in response to 12 articles dealing with H1N1 vaccine on websites of three major Canadian news sources. Articles were selected based on topic and number of comments. A second objective was to assess the extent to which on-line comments can be used as a reliable data source to capture public attitudes during a health crisis. The following seven themes were mentioned in at least 5% of the comments (% indicates the percentage of comments that included the theme): fear of H1N1 (18.8%); responsibility of media (17.8%); government competency (17.7%); government trustworthiness (10.7%); fear of H1N1 vaccine (8.1%); pharmaceutical companies (7.6%); and personal protective measures (5.8%). It is assumed that the more frequently a theme was mentioned, the more that theme influenced decision making about vaccination. These key themes for the public were often not aligned with the issues and information officials perceived, and conveyed, as relevant in the decision making process. The main themes from the comments were consistent with results from surveys and focus groups addressing similar issues, which suggest that on-line comments do provide a reliable source of qualitative data on attitudes and perceptions of issues that emerge in a health crisis. The insights derived from the comments can contribute to improved communication and policy decisions about vaccination in health crises that incorporate the public's views.
Smith and Farah (2011) presented a scholarly review of critical areas related to their intriguing title “Are Prescription Stimulants ‘Smart Pills’?” We contend that they accomplished the main goal of the article, to get the facts straight about possible cognitive enhancement via the nonmedical use of stimulant drugs by individuals without a diagnosis of attention-deficit/hyperactivity disorder (ADHD). At the same time, they justified their main conclusions that (a) individuals are seeking and engaging in nonmedical use of stimulant drugs with the expectations of cognitive enhancement despite uncertainty whether such expectations are valid and (b) on some tasks, there are small average benefits of nonmedical use, but the overall pattern is not clear (e.g., small beneficial effects across most individuals or large beneficial effects only in a few individuals, both of which result in small average effects). We offer comments in 3 areas to amplify key topics mentioned but not emphasized by Smith and Farah: (a) characterization of the cognitive effects of medical use of stimulants to contrast with the cognitive effects of nonmedical use; (b) justification of medical use of stimulants by placement on a normally distributed dimension of behavior rather than categorical diagnosis of ADHD, which varies widely across countries; and (c) evaluation of the potential risks of nonmedical use to individuals and to society (e.g., the likelihood of addiction to stimulant drugs in a small minority of the population) rather than just the potential benefits of cognitive enhancement.
ADHD; stimulant drugs; medical use of stimulants; diversion of stimulants; addiction to stimulants
There is consensus that patients should be told if they are injured by medical care. However, there is little information on how they react to different methods of disclosure.
To determine if volunteers’ reactions to videos of physicians disclosing adverse events are related to the physician apologizing and accepting responsibility.
Survey of viewers randomized to watch videos of disclosures of three adverse events (missed mammogram, chemotherapy overdose, delay in surgical therapy) with designed variations in extent of apology (full, non-specific, none) and acceptance of responsibility (full, none).
Adult volunteer sample from the general community in Baltimore.
Viewer evaluations of physicians in the videos using standardized scales.
Of 200 volunteers, 50% were <40 years, 25% were female, 80% were African American, and 50% had completed high school. For designed variations, scores were non-significantly higher for full apology/responsibility, and lower for no apology/no responsibility. Perceived apology or responsibility was related to significantly higher ratings (chi-square, 81% vs. 38% trusted; 56% vs. 27% would refer, p < 0.05), but inclination to sue was unchanged (43% vs. 47%). In logistic regression analyses adjusting for age, gender, race and education, perceived apology and perceived responsibility were independently related to higher ratings for all measures. Inclination to sue was reduced non-significantly.
Patients will probably respond more favorably to physicians who apologize and accept responsibility for medical errors than those who do not apologize or give ambiguous responses. Patient perceptions of what is said may be more important than what is actually said. Desire to sue may not be affected despite a full apology and acceptance of responsibility.
medical error; disclosure; apology; video; patient perceptions; vignette
In March 1986, the Health Care Financing Administration (HCFA) released ten lists of death-rate "outlier" hospitals, one for all 1984 Medicare discharges and nine for specific DRGs. Recent Medicare hospital discharge abstracts have substantially undercounted in-hospital deaths, with large variations by state. Apart from the proportion of a hospital's cases in 80 DRGs, the predictive models had no measures of case severity based on diagnosis or procedure. Having DRG 123 (all deaths from acute myocardial infarction) as an independent variable in the all-death regression model probably accounted for much of its high r2. Inclusion of an independent variable for average length of stay (ALOS) favored hospitals in higher ALOS states by higher predicted death rates. Model bias also favored lower-risk hospitals. Small numbers of predicted deaths for specific DRGs limited low-volume hospitals on these outlier lists to those with high ratios of actual to predicted deaths. On six of the nine DRG-specific outlier lists, a total 1,222 hospitals had unfavorable residuals, while only 8 were favorable. Ten recommendations are given to increase reliability of future outcome analyses.
Sternberg (2011) elegantly formalizes how certain sets of hypotheses, specifically modularity and pure or composite measures, imply certain patterns of behavioural and neuroimaging data. Experimentalists are often interested in the converse, however: whether certain patterns of data distinguish certain hypotheses, specifically whether more than one module is involved. In this case, there is a striking reversal of the relative value of the data patterns that Sternberg considers. Foremost, the example of additive effects of two factors on one composite measure becomes noninformative for this converse question. Indeed, as soon as one allows for nonlinear measurement functions and nonlinear module processes, even a cross-over interaction between two factors is noninformative in this respect. Rather, one requires more than one measure, from which certain data patterns do provide strong evidence for multiple modules, assuming only that the measurement functions are monotonic. If two measures are not monotonically related to each other across the levels of one or more experimental factors, then one has evidence for more than one module (i.e., more than one nonmonotonic transform). Two special cases of this are illustrated here: a “reversed association” between two measures across three levels of a single factor, and Sternberg's example of selective effects of two factors on two measures. Fortunately, functional neuroimaging methods normally do provide multiple measures over space (e.g., functional magnetic resonance imaging, fMRI) and/or time (e.g., electroencephalography, EEG). Thus to the extent that brain modules imply mind modules (i.e., separate processors imply separate processes), the performance data offered by functional neuroimaging are likely to be more powerful in revealing modules than are the single behavioural measures (such as accuracy or reaction time, RT) traditionally considered in psychology.
Cognitive neuroscience; Cognitive psychology; functional magnetic resonance imaging; Electroencephalography; Dissociations
In their 2009 Nature article: “Anticipatory haemodynamic signals in sensory cortex not predicted by local neuronal activity,” Yevginiy Sirotin and Aniruddha Das suggest that hemodynamic signals, the basis of functional MRI (fMRI), can arise without any measurable neuronal activity. They report that hemodynamic signals in visual cortex were associated with and time-locked to the anticipation of a visual stimulus, and importantly, without any associated neuronal activity as measured with direct electrophysiological recordings. In this commentary, we demonstrate, using an assessment of their own data, that their claims are not strongly supported. In fact, we found that specific LFP frequency ranges predicted with a high degree of accuracy, the “dark” or “anticipatory” hemodynamic response. For other frequency ranges, we found differences in phase but not magnitude of the measured and predicted hemodynamic response. Importantly, when comparing simply the magnitude as well as the time series standard deviation of the electrophysiological recordings with those of the measured hemodynamic responses, we found a direct correspondence of the dark/stimulated magnitude and standard deviation between the electrophysiological recordings and the hemodynamic responses. All of these analyses strongly imply that anticipatory hemodynamic responses are, in fact, accurately predicted in phase and magnitude by several LFP frequency bands, and are predicted in standard deviation and magnitude by the standard deviation and magnitude of even a wider range of LFP frequencies. We argue that rather than casting doubt on fMRI signal changes, these studies open up an interesting window into exploring more subtle neurovascular relationships.
The authors of the World Health Organization Semen Analysis Manual are to be congratulated on producing a new edition; it is an essential tool to disseminate good practice in andrology. However, the tests described have poor prognostic power to predict a man's fertility and show little about the underlying causes of sub-fertility. This commentary urges a revival of research into the diagnosis of male fertility. It suggests that fertility should be regarded as a continuum and that the artificial binary division between fertile and infertile should be abandoned. Models to predict a sub-fertile couple's chance of conception in a year should be developed on the basis of prospective data. These models would allow for sophisticated decision making about management. The future lies in the identification of tests to detect underlying pathologies open to specific treatment. Leads such as oxidative stress, defects in the intracellular regulation and the developing field of proteomics should be explored.
diagnosis; male infertility; oxidative stress; predictive value of tests; sperm count
In a report of a single patient in a persistent vegetative state, Owen et al(1) claim that the presence of task-specific brain activation in response to verbal command implies both covert conscious awareness and a capacity for intention. We argue that neither can be securely inferred from the evidence presented.
This commentary proposes a dynamical systems perspective to re-interpret data from a group of international soccer players demonstrating that wearing textured insoles in soccer boots enhanced tactile information from the sole of the foot and increased movement discrimination capacity in ankle inversion sensitivity tests to levels similar to those in barefoot conditions. Theoretical arguments on the functional role of variability induced in the sensorimotor system by textured insoles, acting as a form of "essential noise" to enhance the accuracy of foot positioning are presented. It seems that, far from interfering with motor performance, variability can actually enhance perception of information to support motor performance. The addition of intermittent, intermediate levels of noise in a perceptual motor context may benefit performers by helping them to pick up information signals from background structure. Movement system variability is conceived as noise induced resonance benefiting the pick up of information to regulate behaviour. Variability can be functional in practical programmes to offset negative effects of losses in sensory sensitivity through ageing, disease, illness, or injury
Recent years have seen a surge in mathematical modeling of the various aspects of neuron–astrocyte interactions, and the field of brain energy metabolism is no exception in that regard. Despite the advent of biophysical models in the field, the long-lasting debate on the role of lactate in brain energy metabolism is still unresolved. Quite the contrary, it has been ported to the world of differential equations. Here, we summarize the present state of this discussion from the modeler's point of view and bring some crucial points to the attention of the non-mathematically proficient reader.
astrocytes; glucose; lactate; mathematical modeling; neuronal–glial interaction
This editorial addresses the debate concerning the origin of adult nucleus pulposus cells in the light of profiling studies by Minogue and colleagues. In their report of several marker genes that distinguish nucleus pulposus cells from other related cell types, the authors provide novel insights into the notochordal nature of the former. Together with recently published work, their work lends support to the view that all cells present within the nucleus pulposus are derived from the notochord. Hence, the choice of an animal model for disc research should be based on considerations other than the cell loss and replacement by non-notochordal cells.
We present a case that demonstrates the rare occurrence of type 1 second-degree atrioventricular block (Wenckebach or Mobitz type 1 block) as a result of block in the infranodal conduction system. This extremely rare occurrence often predicts progression to complete heart block and necessitates cardiac pacing. It also demonstrates the value of an electrophysiological study and exercise stress testing to identify the level of block, predict prognosis, and plan a management strategy.
Salthouse (2011) critically reviewed cross-sectional and longitudinal relations among adult age, brain structure, and cognition (ABC), and identified problems in interpretation of the extant literature. His review, however, misses several important points. First, there is enough disparity among the measures of brain structure and cognitive performance to question the uniformity of B and C vertices of the ABC triangle. Second, age differences and age changes in brain and cognition are often nonlinear. Third, variances and correlations among measures of brain and cognition frequently vary with age. Fourth, cross-sectional comparisons among competing models of ABC associations cannot disambiguate competing hypotheses about the structure and the range of directed and reciprocal relations between changes in brain and behavior. Based on these observations, we offer the following conclusions. First, individual differences among younger adults are not useful for understanding the aging of brain and behavior. Second, only multivariate longitudinal studies, age-comparative experimental interventions, and a combination of the two will deliver us from the predicaments of the ABC triangle described by Salthouse (2011). Mediation models of cross-sectional data represent age-related differences in target variables but fail to approximate time-dependent relations, and thus do not elucidate the dimensions and dynamics of cognitive aging.
brain; aging; cognition; longitudinal; mediation
The nature and significance of equity and equality in relation to health and healthcare policy is discussed in the light of a recent article by Culyer. Culyer makes the following claims: (a) the importance of equity in relation to the provision of health care derives from the human need for health in order to flourish; and (b) for the sake of equity, equality of health among the members of particular political jurisdictions should be the aim of health policy. Both these claims are challenged in this paper.
The argument put forward is that it is only when needs arise and are met in particular contexts that need and equity are fused. The state and its agents and agencies should distribute what it distributes impartially, whatever it distributes. Whether or not equity applies to the distribution of healthcare services depends on how they are provided and not on their nature as "primary goods". Contrary to what Culyer suggests, a policy of trying to produce the outcome of health equality would be inequitable. It would not be impartial and it would fail to treat persons as persons ought to be treated.
Cowan & Rouder suggest that a modification to the four-slot model of visual working memory fits the available data better than our distributed resource model. However their comparisons of statistical fit are biased in favour of the slot model. Here we compare the predictions of the two models and present further evidence against the division of visual memory into slots.