Drug discovery in neurodegenerative diseases

This meeting report documents the exciting ongoing research aimed at developing new therapeutic agents for neurodegenerative diseases at the interface between academia and industry, and illustrates the direction the NIH "roadmap" for medical research is taking. Some of the projects have resulted in very promising drugs, identified and developed by academic centers, entering clinical trials.     

Hierarchical Gaussian process mixtures for regression

As a result of their good performance in practice and their desirable analytical properties, Gaussian process regression models are becoming increasingly of interest in statistics, engineering and other fields. However, two major problems arise when the model is applied to a large data-set with repeated measurements. One stems from the systematic heterogeneity among the different replications, and the other is the requirement to invert a covariance matrix which is involved in the implementation of the model. The dimension of this matrix equals the sample size of the training data-set. In this paper, a Gaussian process mixture model for regression is proposed for dealing with the above two problems, and a hybrid Markov chain Monte Carlo (MCMC) algorithm is used for its implementation. Application to a real data-set is reported.     

Vital Involvement Practice: strengths as more than tools for solving problems

This article describes Vital Involvement Practice, a strength-based approach to clinical practice with elders, including those who are extremely frail. Using this approach, practitioners have been able to help elders increase later-life vitality and associated positive quality of life through: (1) systematic identification of individual strengths and assets (found both in the person and in the surrounding environment), and (2) consideration of these strengths alongside the individual and environmental deficits that are the subject of most geriatric practice. The approach utilizes original data-gathering tools (Occupational Profile; Life Strengths Interview Guide) and a stepwise, worksheet- structured consideration of these data in order to formulate action strategies for achieving client goals (Domain Scan; Domain Goals; Life Plan/Strategy). All elements of VIP emerged in pilot work with gerontological practitioners and their elder clients in such settings as: primary health care; government social service; subsidized senior housing; private clinical practice; community recreation. Limitations, implications, and promise are noted, with respect to practice and research.     

Community Structure and the Mobilization of Support

Grâce à l'étude d'un mouvement social en faveur de l'incorporation de deux banlieues dans une agglomération, les auteurs examinent le succès du leadership à s'assurer l'appui populaire en rapport avec les structures sociales de la communauté. Leur analyse indique que l'obtention de cet appui est affecté par deux ensembles de conditions. Premièrement, les dispositions structurales qui contribuent à la communauté. Leur analyse collectivité nuisent aux leaders dans leur tâche alors que celles qui l'intègrent morphologiquement la facilitent. En second lieu, la position sociale de ceux qui assument la direction du mouvement et leurs liens avec divers organismes communautaires affectent aussi leurs possibilités de mobiliser l'appui populaire qu'ils souhaitent.     

Heaping in anniversary reaction studies: a cautionary note

Several studies have reported evidence that death is often associated with significant ceremonial events like holidays and birthdays, a phenomenon variously called the "anniversary reaction," "holiday effect," "birthday blues," etc. This article, using data from the social security death index (SSDI), shows how evidence for this phenomenon can arise from an artifact in death records called "death heaping" in which certain dates, usually the 1st or the 15th, are systematically entered for missing data. In this study, each calendar birthday for the year 2003 in the SSDI was paired with either the 14th or 15th calendar day of death. For each pairing, there were more deaths for the 15th than the 14th. A second analysis compared the correspondence between dying on the same day of the month as one's birthday for the first 28 days of the month. A significantly greater number of birth-death combinations occurred for the 1st and 15th day of the month. These results suggest that studies of "anniversary reactions" should conduct preliminary evaluations to consider the possibility that statistically significant relationships do not arise from "death heaping."     

Analysis of ordered categorical data with score averaging: with applications to case-control genetic associations

The trend test is often used for the analysis of 2×K ordered categorical data, in which K pre-specified increasing scores are used. There have been discussions on how to assign these scores and the impact of the outcomes on different scores. The scores are often assigned based on the data-generating model. When this model is unknown, using the trend test is not robust. We discuss the weighted average of a trend test over all scientifically plausible choices of scores or models. This approach is more computationally efficient than a commonly used robust test MAX when K is large. Our discussion is for any ordered 2×K table, but simulation and applications to real data are focused on case-control genetic association studies. Although there is no single test optimal for all choices of scores, our numerical results show that some score averaging tests can achieve the performance of MAX.     

A general algorithm for computing simultaneous prediction intervals for the (log)-location-scale family of distributions

Making predictions of future realized values of random variables based on currently available data is a frequent task in statistical applications. In some applications, the interest is to obtain a two-sided simultaneous prediction interval (SPI) to contain at least k out of m future observations with a certain confidence level based on n previous observations from the same distribution. A closely related problem is to obtain a one-sided upper (or lower) simultaneous prediction bound (SPB) to exceed (or be exceeded) by at least k out of m future observations. In this paper, we provide a general approach for computing SPIs and SPBs based on data from a particular member of the (log)-location-scale family of distributions with complete or right censored data. The proposed simulation-based procedure can provide exact coverage probability for complete and Type II censored data. For Type I censored data, our simulation results show that our procedure provides satisfactory results in small samples. We use three applications to illustrate the proposed simultaneous prediction intervals and bounds.     

The population situation in Africa]

The population growth rate in Africa has been the highest in the world since 1970--about 2.7% annually. A lower mortality rate because of better health conditions, their tradition of early marriage and polygamy, and the predominantly agricultural economy are the main reasons. The lack of coordination of such rapid population growth with the slow economic development and backward industrial and agricultural conditions have caused a very serious unemployment problem and inhibit increases in the living standard. The vast areas of desert and equatorial forest are sparsely inhabited. The coastline, Nile delta, and the plateaus are the most densely populated areas of the world. The abnormally developed cities cause expansion of the urban population and serious problems in employment, housing, traffic, health, and education. Many leaders of African countries have begun to realize the seriousness of the rapid population growth, and a few have begun family planning programs. Most countries have no official policies concerning population control and a few even encourage population growth.