Does Medicare Save Lives?

The health insurance characteristics of the population changes sharply at age 65 as most people become eligible for Medicare. But do these changes matter for health? We address this question using data on over 400,000 hospital admissions for people who are admitted through the emergency room for "non-deferrable" conditions -- diagnoses with the same daily admission rates on weekends and weekdays. Among this subset of patients there is no discernible rise in the number of admissions at age 65, suggesting that the severity of illness is similar for patients on either side of the Medicare threshold. The insurance characteristics of the two groups are much different, however, with a large jump at 65 in the fraction who have Medicare as their primary insurer, and a reduction in the fraction with no coverage. These changes are associated with significant increases in hospital list chargers, in the number of procedures performed in hospital, and in the rate that patients are transferred to other care units in the hospital. We estimate a nearly 1 percentage point drop in 7-day mortality for patients at age 65, implying that Medicare eligibility reduces the death rate of this severely ill patient group by 20 percent. The mortality gap persists for at least two years following the initial hospital admission.

The Impact of Nearly Universal Insurance Coverage on Health Care Utilization and Health: Evidence from Medicare

We use the increases in health insurance coverage at age 65 generated by the rules of the Medicare program to evaluate the effects of health insurance coverage on health related behaviors and outcomes. The rise in overall coverage at age 65 is accompanied by a narrowing of disparities across race and education groups. Groups with bigger increases in coverage at 65 experience bigger reductions in the probability of delaying or not receiving medical care, and bigger increases in the probability of routine doctor visits. Hospital discharge records also show large increases in admission rates at age 65, especially for elective procedures like bypass surgery and joint replacement. The rises in hospitalization are bigger for whites than blacks, and for residents of areas with higher rates of insurance coverage prior to age 65, suggesting that the gains arise because of the relative generosity of Medicare, rather than the availability of insurance coverage. Finally, there are small impacts of reaching age 65 on self-reported health, with the largest gains among the groups that experience the largest gains in insurance coverage. In contrast we find no evidence of a shift in the rate of growth of mortality rates at age 65.

Applied computational geometry: Towards robust solutions of basic problems

AbstractGeometric computations, like all numerical procedures, are extremely prone to roundoff error. However, virtually none of the numerical analysis literature directly applies to geometric calculations. Even for line intersection, the most basic geometric operation, there is no robust and efficient algorithm. Compounding the difficulties, many geometric algorithms perform iterations of calculations reusing previously computed data. In this paper, we explore some of the main issues in geometric computations and the methods that have been proposed to handle roundoff errors. In particular, we focus on one method and apply it to a general iterative intersection problem. Our initial results seem promising and will hopefully lead to robust solutions for more complex problems of applied computational geometry

Fast detection of polyhedral intersection

AbstractMethods are given for unifying and extending previous work on detecting intersections of suitably preprocessed polyhedra. New upper bounds of O(log n) and O(log2 n) are given on plane-polyhedron and polyhedron-polyhedron intersection problems

Partitioning space for range queries

It is shown that, given a set S of n points in R3, one can always find three planes that form an eight-partition of S, that is, a partition where at most n/8 points of S lie in each of the eight open regions. This theorem is used to define a data structure, called an octant tree, for representing any point set in R3. An octant tree for n points occupies O(n) space and can be constructed in polynomial time. With this data structure and its refinements, efficient solutions to various range query problems in 2 and 3 dimensions can be obtained, including (1) half-space queries: find all points of S that lie to one side of any given plane; (2) polyhedron queries: find all points that lie inside (outside) any given polyhedron; and (3) circular queries in R2: for a planar set S, find all points that lie inside (outside) any given circle. The retrieval time for all these queries is T(n)=O(na + m) where a= 0.8988 (or 0.8471 in case (3)) and m is the size of the output. This performance is the best currently known for linear-space data structures which can be deterministically constructed in polynomial time

Beta-Skeletons have Unbounded Dilation

A fractal construction shows that, for any beta>0, the beta-skeleton of a point set can have arbitrarily large dilation. In particular this applies to the Gabriel graph.Comment: 8 pages, 9 figure

Archiving of data on occurrence of breeding birds associated with fire treatments and controls

Since 2001, we have collected data on occupancy and relative abundance of Greater Sage- Grouse (Centrocercus urophasianus) and other species of breeding birds in the central Great Basin, and characterized the vegetation structure and composition of breeding birds’ habitats, through four projects supported by the Joint Fire Science Program (00-2-15, 01B-3-3-01, 05-2-1- 94, and 09-1-08-4). These projects collectively have generated dozens of refereed publications, dozens of invited papers or presentations, multiple M.S. theses and Ph.D. dissertations, and many workshops and field tours. Bird data included in refereed publications to date were based on point counts with a fixed radius of 75 or 100 m and a duration of 5 minutes per visit. These data previously were archived with the USDA Forest Service’s Research Data Archive. Since 2004, however, we also have conducted 100-m fixed-radius point counts with a duration of 8 minutes per visit. Furthermore, starting in 2002, we recorded birds detected beyond the fixed radius and during travel among point-count locations or at other times of day or night. We archived data on the incidental and longer-distance detections of birds, which included more than 22,600 records. We also archived all data on vegetation structure and the composition of dominant trees and shrubs collected through 2012. There are few sets of long-term, spatially extensive data on distributions and abundance of fauna or extensive characterizations of vegetation in the Great Basin. These data have considerable capacity to inform understanding and management of fire dynamics; changes in land cover, including conversion of native vegetation to cheatgrass (Bromus tectorum); and the status of species proposed for listing under the Endangered Species Act

Physical Activity and Hippocampal Sub-Region Structure in Older Adults with Memory Complaints.

BackgroundPhysical activity (PA) plays a major role in maintaining cognition in older adults. PA has been shown to be correlated with total hippocampal volume, a memory-critical region within the medial temporal lobe (MTL). However, research on associations between PA and MTL sub-region integrity is limited.ObjectiveTo examine the relationship between PA, MTL thickness, and its sub-regions, and cognitive function in non-demented older adults with memory complaints.MethodsTwenty-nine subjects aged ≥60 years, with memory complaints were recruited for this cross-sectional study. PA was tracked for 7 days using accelerometers, and average number of steps/day determined. Subjects were categorized into two groups: those who walked ≤4000 steps/day (lower PA) and those with >4000 steps/day (higher PA). Subjects received neuropsychological testing and 3T MRI scans. Nonparametric ANCOVAs controlling for age examined differences between the two groups.ResultsTwenty-six subjects aged 72.7(8.1) years completed the study. The higher PA group (n = 13) had thicker fusiform gyrus (median difference = 0.11 mm, effect size (ES) = 1.43, p = 0.001) and parahippocampal cortex (median difference = 0.12 mm, ES = 0.93, p = 0.04) compared to the lower PA group. The higher PA group also exhibited superior performance in attention and information-processing speed (median difference = 0.90, ES = 1.61, p = 0.003) and executive functioning (median difference = 0.97, ES = 1.24, p = 0.05). Memory recall was not significantly different between the two groups.ConclusionOlder non-demented individuals complaining of memory loss who walked >4000 steps each day had thicker MTL sub-regions and better cognitive functioning than those who walked ≤4000 steps. Future studies should include longitudinal analyses and explore mechanisms mediating hippocampal related atrophy