Claire E. Pavlik

An Experimental Comparison of Ordinary and Universal Kriging and Inverse Distance Weighting

A factorial, computational experiment was conducted to compare the spatial interpolation accuracy of ordinary and universal kriging and two types of inverse squared-distance weighting. The experiment considered, in addition to these four interpolation methods, the effects of four data and sampling characteristics: surface type, sampling pattern, noise level, and strength of small-scale spatial correlation. Interpolation accuracy was measured by the natural logarithm of the mean squared interpolation error. Main effects of all five factors, all two-factor interactions, and several three-factor interactions were highly statistically significant. Among numerous findings, the most striking was that the two kriging methods were substantially superior to the inverse distance weighting methods over all levels of surface type, sampling pattern, noise, and correlation.

The Aftermath of Hip Fracture: Discharge Placement, Functional Status Change, and Mortality

The authors prospectively explored the consequences of hip fracture with regard to discharge placement, functional status, and mortality using the Survey on Assets and Health Dynamics Among the Oldest Old (AHEAD). Data from baseline (1993) AHEAD interviews and biennial follow-up interviews were linked to Medicare claims data from 1993-2005. There were 495 postbaseline hip fractures among 5,511 respondents aged >or=69 years. Mean age at hip fracture was 85 years; 73% of fracture patients were white women, 45% had pertrochanteric fractures, and 55% underwent surgical pinning. Most patients (58%) were discharged to a nursing facility, with 14% being discharged to their homes. In-hospital, 6-month, and 1-year mortality were 2.7%, 19%, and 26%, respectively. Declines in functional-status-scale scores ranged from 29% on the fine motor skills scale to 56% on the mobility index. Mean scale score declines were 1.9 for activities of daily living, 1.7 for instrumental activities of daily living, and 2.2 for depressive symptoms; scores on mobility, large muscle, gross motor, and cognitive status scales worsened by 2.3, 1.6, 2.2, and 2.5 points, respectively. Hip fracture characteristics, socioeconomic status, and year of fracture were significantly associated with discharge placement. Sex, age, dementia, and frailty were significantly associated with mortality. This is one of the few studies to prospectively capture these declines in functional status after hip fracture.

Geocoding Health Data : The Use of Geographic Codes in Cancer Prevention and Control, Research and Practice

Introduction Geocoding Methods, Materials, and First Steps toward a Geocoding Error Budget M.P. Armstrong and C. Tiwari Using ZIP codes as Geocodes in Cancer Research K.M.M. Beyer, A.F. Schultz, and Z. Chen Producing Spatially Continuous Prostate Cancer Maps with Different Geocodes and Spatial Filter Methods G. Rushton, Q. Cai, and Z. Chen The Science and Art of Geocoding: Tips for Improving Match Rates and Handling Unmatched Cases in Analysis F. Boscoe Geocoding Practices in Cancer Registries T. Abe and D. Stinchcomb Alternative Techniques for Masking Geographic Detail to Protect Privacy D.L. Zimmerman, M.P. Armstrong, and Gerard Rushton Preserving Privacy: Deidentifying Data by Applying a Random Perturbation Spatial Mask Z. Chen, G. Rushton, and G. Smith Spatial Statistical Analysis of Point- and Area-Reference Public Health Data L.A. Waller Statistical methods for Incompletely and Incorrectly Geocoded Cancer Data D. L. Zimmerman Using Geocodes to estimate Distances and geographic Accessibility for Cancer Prevention and Control M. Armstrong, B. Greene, and G. Rushton Cancer Registry Data and Geocoding: Privacy, Confidentiality, and Security Issues J. Gittler Conclusions Appendix: Cancer Reporting and Registry Statutes and Regulations J. Gittler

Recent Hospitalization and the Risk of Hip Fracture Among Older Americans

BACKGROUND We identified hip fracture risks in a prospective national study. METHODS Baseline (1993-1994) interview data were linked to Medicare claims for 1993-2005. Participants were 5,511 self-respondents aged 70 years and older and not in managed Medicare. ICD9-CM 820.xx (International Classification of Diseases, 9th Edition, Clinical Modification) codes identified hip fracture. Participants were censored at death or enrollment into managed Medicare. Static risk factors included sociodemographic, socioeconomic, place of residence, health behavior, disease history, and functional and cognitive status measures. A time-dependent marker reflecting postbaseline hospitalizations was included. RESULTS A total of 495 (8.9%) participants suffered a postbaseline hip fracture. In the static proportional hazards model, the greatest risks involved age (adjusted hazard ratios [AHRs] of 2.01, 2.82, and 4.91 for 75-79, 80-84, and > or =85 year age groups vs those aged 70-74 years; p values <.001), sex (AHR = 0.45 for men vs women; p < .001), race (AHRs of 0.37 and 0.46 for African Americans and Hispanics vs whites; p values <.001 and <.01), body mass (AHRs of 0.40, 0.77, and 1.73 for obese, overweight, and underweight vs normal weight; p values <.001, <.05, and <.01), smoking status (AHRs = 1.49 and 1.52 for current and former smokers vs nonsmokers; p values <.05 and <.001), and diabetes (AHR = 1.99; p < .001). The time-dependent recent hospitalization marker did not alter the static model effect estimates, but it did substantially increase the risk of hip fracture (AHR = 2.51; p < .001). CONCLUSIONS Enhanced discharge planning and home care for non-hip fracture hospitalizations could reduce subsequent hip fracture rates.

The use of chiropractors by older adults in the United States

BackgroundIn a nationally representative sample of United States Medicare beneficiaries, we examined the extent of chiropractic use, factors associated with seeing a chiropractor, and predictors of the volume of chiropractic use among those having seen one.MethodsWe performed secondary analyses of baseline interview data on 4,310 self-respondents who were 70 years old or older when they first participated in the Survey on Assets and Health Dynamics Among the Oldest Old (AHEAD). The interview data were then linked to their Medicare claims. Multiple logistic and negative binomial regressions were used.ResultsThe average annual rate of chiropractic use was 4.6%. During the four-year period (two years before and two years after each respondents baseline interview), 10.3% had one or more visits to a chiropractor. African Americans and Hispanics, as well as those with multiple depressive symptoms and those who lived in counties with lower than average supplies of chiropractors were much less likely to use them. The use of chiropractors was much more likely among those who drank alcohol, had arthritis, reported pain, and were able to drive. Chiropractic services did not substitute for physician visits. Among those who had seen a chiropractor, the volume of chiropractic visits was lower for those who lived alone, had lower incomes, and poorer cognitive abilities, while it was greater for the overweight and those with lower body limitations.ConclusionChiropractic use among older adults is less prevalent than has been consistently reported for the United States as a whole, and is most common among Whites, those reporting pain, and those with geographic, financial, and transportation access.

Defining emergency department episodes by severity and intensity: A 15-year study of Medicare beneficiaries

BackgroundEpisodes of Emergency Department (ED) service use among older adults previously have not been constructed, or evaluated as multi-dimensional phenomena. In this study, we constructed episodes of ED service use among a cohort of older adults over a 15-year observation period, measured the episodes by severity and intensity, and compared these measures in predicting subsequent hospitalization.MethodsWe conducted a secondary analysis of the prospective cohort study entitled the Survey on Assets and Health Dynamics among the Oldest Old (AHEAD). Baseline (1993) data on 5,511 self-respondents ≥70 years old were linked to their Medicare claims for 1991-2005. Claims then were organized into episodes of ED care according to Medicare guidelines. The severity of ED episodes was measured with a modified-NYU algorithm using ICD9-CM diagnoses, and the intensity of the episodes was measured using CPT codes. Measures were evaluated against subsequent hospitalization to estimate comparative predictive validity.ResultsOver 15 years, three-fourths (4,171) of the 5,511 AHEAD participants had at least 1 ED episode, with a mean of 4.5 episodes. Cross-classification indicated the modified-NYU severity measure and the CPT-based intensity measure captured different aspects of ED episodes (kappa = 0.18). While both measures were significant independent predictors of hospital admission from ED episodes, the CPT measure had substantially higher predictive validity than the modified-NYU measure (AORs 5.70 vs. 3.31; p < .001).ConclusionsWe demonstrated an innovative approach for how claims data can be used to construct episodes of ED care among a sample of older adults. We also determined that the modified-NYU measure of severity and the CPT measure of intensity tap different aspects of ED episodes, and that both measures were predictive of subsequent hospitalization.

Parallel processing of spatial statistics

The computational intensity of spatial statistics, including measures of spatial association, has hindered their application to large empirical data sets. Computing environments using parallel processing have the potential to eliminate this problem. In this paper, we develop a method for processing a computationally intensive measure of spatial association (G) in parallel and present the performance enhancements obtained. Timing results are presented for a single processor and for 2–14 parallel processors operating on data sets containing 256–1600 point observations. The results indicate that significant improvements in processing time can be achieved using parallel architectures.

A 12-year prospective study of stroke risk in older Medicare beneficiaries

Background5.8 M living Americans have experienced a stroke at some time in their lives, 780K had either their first or a recurrent stroke this year, and 150K died from strokes this year. Stroke costs about

Large Firm Strategies: Spatial Patterns of Production

66B annually in the US, and also results in serious, long-term disability. Therefore, it is prudent to identify all possible risk factors and their effects so that appropriate intervention points may be targeted.MethodsBaseline (1993–1994) interview data from the nationally representative Survey on Assets and Health Dynamics among the Oldest Old (AHEAD) were linked to 1993–2005 Medicare claims. Participants were 5,511 self-respondents ≥ 70 years old. Two ICD9-CM case-identification approaches were used. Two approaches to stroke case-identification based on ICD9-CM codes were used, one emphasized sensitivity and the other emphasized specificity. Participants were censored at death or enrollment into managed Medicare. Baseline risk factors included sociodemographic, socioeconomic, place of residence, health behavior, disease history, and functional and cognitive status measures. A time-dependent marker reflecting post-baseline non-stroke hospitalizations was included to reflect health shocks, and sensitivity analyses were conducted to identify its peak effect. Competing risk, proportional hazards regression was used.ResultsPost-baseline strokes occurred for 545 (9.9%; high sensitivity approach) and 374 (6.8%; high specificity approach) participants. The greatest static risks involved increased age, being widowed or never married, living in multi-story buildings, reporting a baseline history of diabetes, hypertension, or stroke, and reporting difficulty picking up a dime, refusing to answer the delayed word recall test, or having poor cognition. Risks were similar for both case-identification approaches and for recurrent and first-ever vs. only first-ever strokes. The time-dependent health shock (recent hospitalization) marker did not alter the static model effect estimates, but increased stroke risk by 200% or more.ConclusionThe effect of our health shock marker (a time-dependent recent hospitalization indicator) was large and did not mediate the effects of the traditional risk factors. This suggests an especially vulnerable post-hospital transition period from adverse effects associated with both their underlying health shock (the reasons for the recent hospital admission) and the consequences of their treatments.

Introducing Students to Plant Geography: Polar Ordination Applied to Hanging Gardens.

Views of national economic development and firm evolution that predominated through the early 1970s emphasized stable sequences of developmental stages through which leading nations or firms had passed. Less industrialized nations, if successful, were expected to pass through these same stages. Because the technical and social infrastructure associated with each developmental stage were known in the case of the lead countries, “followers” might be able to decrease the length of each individual stage, thus climbing the development ladder more quickly. For firms, a similar evolutionary model of industrial organization dominated. In this case, however, the description of development focused primarily on leading firms that grew to dominate industrial branches or sectors. In the case of firms, conditions in the market were expected to operate such that the “best” firms developed through a sequence, culminating in a particular organizational form. Firms with inadequate resources, less able management, or poor competitive positions, on the other hand, were expected to remain at lower stages in the sequence unless conditions changed.