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The objectives of this report are to document methods used to identify health service areas for the United States and to describe and evaluate these areas. A health service area is defined as one or more counties that are relatively self-contained with respect to the provision of routine hospital care. Service areas that include more than one county are characterized by travel between the counties for routine hospital care.
Studies have suggested increases in hospitalization for asthma and in asthma mortality during the early 1980s. Using US Vital Records, we examined asthma mortality from 1968 through 1987 to describe the rates of change among children and young adults (aged 5 to 34 years) with time and in small geographic areas. During the 1970s, US asthma mortality declined by 7.8% per annum (+/- 1.0%), declining faster among women and nonwhites. During the 1980s, mortality increased by 6.2% per annum (+/- 1.2%), increasing faster among those aged 5 to 14 years than among those aged 15 to 34 years. Small-area geographic analysis revealed four areas with persistently high asthma mortality. Neither changes in International Classification of Diseases coding nor improved recognition of asthma, as demonstrated by trends in autopsy rates or rates of in-hospital deaths, seems to explain the increasing mortality of the 1980s.
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OBJECTIVE: Our purpose is a descriptive analysis of variations in hospital use among small areas of Maryland. DATA SOURCE: The data are Maryland patient discharge records from acute care hospitals for 1985-1987 and small area population estimates by age, gender, race, and income. FINDINGS: The common finding was excess geographic variability among Maryland's 115 areas. The hypothesis of uniform rates was rejected for most DRGs, including low-variation mastectomy and hernia repair. Clustering of high-use rates occurred in neighboring areas for orthopedic, vascular, and elective procedures. Admission rates for most nondiscretionary procedures and medical DRGs were reduced in affluent areas while discretionary surgery increased with income level. Elective procedures had extreme variation and were related to income. Coronary artery disease rates declined with income while coronary artery procedure rates increased, indicating that access and patient selection were factors in the use of coronary bypass and angioplasty. CONCLUSIONS: The issue is not the ubiquitous variation among small areas but its extent and identification of geographic patterns. Hospital use is related to demography, morbidity, medical resources, access, selection for care, and physician practice patterns. Heterogeneity of these factors ensures that uniform delivery of health care rarely holds. There is little evidence that incidence of surgical disease is the main source of variation in use of discretionary surgery. Rather, variations reflect differing medical opinion on appropriate use. Without evaluation, excessive use cannot be distinguished from underservice. Morbidity explains the variability of nondiscretionary surgery and conditions related to lifestyle. Access plays an important role for discretionary surgery. Geographic analysis can identify variation and relate incidence to socioeconomic and specific local effects. Hospital data do not permit direct assessment of appropriate care. Understanding the reasons for variation requires information beyond incidence data. The challenge is to identify and explain small area variations or to fix them.
Small area variation analysis is a research tool used by health services researchers to describe how rates of health care use and events vary over well-defined geographic areas. Significant variation has been shown to exist in the rates of hospitalization for chronic obstructive lung disease, pneumonia, hypertension, and in surgical procedures, such as hysterectomy, cholecystectomy, and tonsillectomy. Potential sources of variation include differences in underlying morbidity, access to care, physician judgment, quality of care delivered, patient demand for services, and random variation. Small area variation studies have been used to determine if significant variation exists across geographic areas and to describe relationships between the observed variation and potential causal factors. Methodologic concerns include the definition of small areas, defining the at-risk population within each small area, sample size, case mix adjustments, and stability of rates over time. The use of small area analysis in primary care will require definition of appropriate small areas for ambulatory care, description of the variation in ambulatory events across small areas, development of appropriate measures for ambulatory case mix, and development of appropriate tools to measure the outcomes of ambulatory care.
OBJECTIVE: To assess interregional differences in the utilization of abortion services in Ontario from 1985 to 1992. DESIGN: Retrospective analysis of provincial therapeutic abortion database. SETTING: All hospitals conducting abortions between 1985 and 1992 and all free-standing abortion clinics conducting abortions between 1990 and 1992. POPULATION: All women in Ontario aged 15 to 44 years who underwent a therapeutic abortion in Ontario during the study period. OUTCOME MEASURES: Utilization of abortion services by county and age-specific abortion rates by county of residence. RESULTS: From 1985 to 1989, when only hospital data were gathered, the mean therapeutic abortion rate increased by 11.2%. From 1990 to 1992, when data from hospitals and free-standing clinics were collected, the mean rate increased by 26.5%. Logistic regression analysis showed significant variation in the age-standardized abortion rates between counties in each study year (p < 0.0001). The counties with age-standardized rates below the 25th percentile had the highest proportions of women who sought abortion services outside their county of residence; in some of these counties no abortions were performed in local facilities. CONCLUSION: There are interregional variations in the utilization of abortion services in Ontario. These disparities raise questions about the accessibility of abortion services and need to be further investigated.
Despite recent advances in the available statistical methods for geographical analysis, there are many constraints to their application in environmental epidemiology. These include problems of data availability and quality, especially the lack in most situations of environmental exposure measurements. Methods for disease 'cluster' investigation, point source exposures, small-area disease mapping and ecological correlation studies are critically reviewed, with the emphasis on practical applications and epidemiological interpretation. It is shown that, unless dealing with rare diseases, high specificity exposures and high relative risks, cluster investigation is unlikely to be fruitful, and is often complicated by the post hoc nature of such studies. However, it is recognized that in these circumstances proper assessment of the available data is often required as part of the public health response. Newly available methods, particularly in Bayesian statistics, offer an appropriate framework for geographical analysis and disease mapping. Again, it is uncertain whether they will give important clues as to aetiology, although they do give valuable description. Perhaps the most satisfactory approach is to test a priori hypotheses using a geographical database, although problems of interpretation remain.
This paper examines the extent to which changes (prospective payment, alternative delivery systems, etc.) in the hospital environment and the general decline in hospital days affect small-area variations in hospital use rates for 18 selected diagnoses in nine hospital service areas in Connecticut. After adjusting for coding changes between DRGs, we found that variation across the service areas did not, in general, differ for any one of the years 1981-86. In one instance (cardiac catheterization), however, we found that a DRG-specific change in knowledge and technology decreased the extent of small-area variation for that diagnosis.
The objectives of this study were: (i) to determine variability among colour parameters of five different ceramic crown systems; and (ii) to measure the effect of using coloured luting agents on restoration colour. The crown systems studied were Cerestore, Dicor, Hi-Ceram, Renaissance, and Vitadur-N. Five crowns for each system were made according to manufacturer's instructions with the same nominal shade (Vita Lumin Vacuum A2) to fit an Ivorine central incisor tooth. Restoration thickness was adjusted to within +/- 0.1 mm (+/- 0.05 mm in the mid-facial area where colour measurements were to be made) with the aid of a dial calliper prior to glazing or, in the case of Dicor, surface staining. Where a core was part of the system this was fabricated to the minimum recommended thickness. The crowns were cemented using luting agents of five different colours in a randomly chosen sequence. The colour of each restoration/cement combination was measured three times using a small-area colorimeter (Minolta CR-121). The variance of each colour parameter (L*, a*, b*) was statistically compared for each crown system using an analysis of variance procedure, as was the effect of the cement. Observed differences were related to visual perception by using the colour difference formula. There were statistically significant differences among the variances of the crown systems and the cements, with significant interactions between crown systems and direction of colour and between cement and direction of colour. Restorations made with different ceramic crown systems had noticeably different colour despite having the same nominal shade. Changing the shade of the luting agent had a perceivable effect on Dicor crowns and, to a lesser extent, on Vitadur-N crowns but not on the other systems due, presumably, to the opacity of their core materials.
Although numerous studies have been made of the determinants of small-area variation in hospital discharge rates, there is still disagreement about the role of socioeconomic factors. The lack of consensus stems, in part, from the difficulty in comparing results across studies that use different units and methods of analysis. Many of the studies using well-defined hospital service areas did not have the data needed to conduct a controlled analysis of the determinants of hospital utilization. Most of the studies that have performed controlled analyses have relied on larger geopolitical areas, which are not believed to capture self-contained health care systems. The study described here used a consistent set of data, three methods of analysis, and two units of analysis to test the importance of socioeconomic characteristics in explaining the variation in medical and surgical discharge rates in Michigan. Socioeconomic factors are found to be statistically significant determinants of the variation in both medical and surgical discharge rates, whether the method of analysis is simple correlations or multiple regressions, and whether the unit of analysis is the county or a well-designed hospital service area. These results suggest that previous small-area variation studies may have incorrectly concluded that socioeconomic characteristics do not explain differences in utilization rates.
Published in 1975, the Atlas of Cancer Mortality for U.S. Counties: 1950-1969 proved useful in identifying geographic patterns, especially clusters of high-rate areas, that have stimulated further epidemiologic study of specific cancer sites. These data have been updated to include population and mortality statistics through 1980. Our new atlas presents static maps of area-specific mortality rates for each decade from 1950 to 1980 among white males and females for 33 cancer sites, along with dynamic maps illustrating the trends in these rates over time. Although the geographic distribution of mortality rates has become more uniform for most cancer sites, clusters of high-rate areas have persisted for several common tumors. However, some new patterns have appeared, notably the emergence of several high-rate areas for lung cancer among women. Possible explanations for the geographic peculiarities of cancer are considered, based on the results of correlation and analytic studies prompted by the earlier maps. These successive studies indicate the value of monitoring mortality statistics on a small-area scale as a strategy for generating etiologic clues and targeting epidemiologic research, although one must be mindful of geographic fluctuations in diagnostic and reporting practices, survival rates, and migration patterns.
The purpose of this study was to examine the electrochemical behavior of silver points in vivo. The apices of silver points removed from teeth with successful or failed endodontic treatments were subjected to complete surface characterization by small-area ESCA, scanning electron microscopy, and electron probe microanalyzer. Cross-sections of the points near the apex were examined with scanning electron microscopy and electron probe microanalyzer to identify the depth of corrosion involvement. According to the results, all silver points manifested evidence of corrosion attack. Electron probe microanalyzer showed no difference in the elemental distribution found on the points. ESCA analysis of the uppermost 5-nm point layer revealed the presence of N on silver points removed from failed treatments. The examination of cross-sections manifested deep S penetration in the bulk of the points removed from failed treatments. Considering the results of this study, no direct association seems to exist between the extent of the corrosion involvement and the prognosis of the treatment. Handling factors and the presence of bacteria are probably the parameters determining the outcome of a treatment.
The effect of opacity on the colorimetric responses of large-area and small-area colorimeters was determined using an elastomer intended for maxillofacial prosthetics use and containing various pigments at different concentrations. Opacity was determined by calculating the contrast ratio of 2-mm-thick specimens against black and white backings, using Kubelka-Munk analyses to correct for thickness and backing color variations. The measure of comparison of the two colorimeters was the relative difference in tristimulus reflectance, with the tristimulus reflectance of the large-area colorimeter as the basis of the relative difference. A significant quadratic relationship was found between contrast ratio and the relative difference in tristimulus reflectance. This relationship may be used to describe opacity without the need to make optical observations or measurements of a thin layer of material on contrasting backings. The small-area colorimeter produced color parameters that are a measure of the combined effects of both color and opacity. The importance of beam size considerations of optical measuring devices for translucent natural and prosthetic materials was emphasized.
The shades of several resin composite materials are keyed to the Vita Lumin shade guide. This study was designed to determine whether different composites of the same designated Vita shade were actually similar in color. A small-area colorimeter was used to compare the L*a*b* color parameters of three hybrid resin composites--Pertac-Hybrid, Prisma AP.H, and XRV Herculite. Four Vita shades (A2, B3, C2, and D3) of each material were evaluated. Color differences (delta E values) between composites of the same designated shade ranged from 2.07 for the A2 shades of Herculite and AP.H to 7.64 for the D3 shades of Herculite and Pertac. Color differences in this range are perceptible to many observers under ideal viewing conditions.
Tooth color is determined by the paths of light inside the tooth and absorption along these paths. This paper tests the hypothesis that, since the paths are determined by scattering, a relation between color and scattering coefficients exists. One hundred and two extracted incisors were fixed in formalin, mounted in a standardized position in brass holders, and pumiced. A facet was prepared near the incisal edge on the labial plane to allow for Knoop hardness measurements with a 500-gram load. Light scattering by the enamel was measured in a 45 degrees/0 degrees geometry; light scattering by both enamel and dentin was measured in a 0 degrees/0 degrees geometry. The reflection spectrum of the tooth was measured from the labial plane with a spectroradiometer in a 45 degrees/0 degrees geometry, with standard illuminant A and standard illuminant D65. To include all volume-reflected light, we used entire-tooth illumination and small-area measurement. CIELAB color coordinates were calculated from the spectra. Neither spectra nor coordinates showed evidence of a contribution of fluorescence to tooth color. Averaged values and standard deviations for L*,a*,b* were 69.9 (4.1), 1.22 (1.4), and 17.9 (2.9), respectively. Both scattering coefficients averaged to 0.6 (0.4) mm-1; Knoop hardness number was, on average, 271 (39) kg/mm2. L* correlated with a* (r = -0.51), with the enamel scattering coefficient (r = 0.60), and slightly with hardness (r = 0.17, p = 0.03). The colors of 28 teeth from which the enamel was removed correlated strongly with the colors of the complete tooth.(ABSTRACT TRUNCATED AT 250 WORDS)
Health care planning requires characterization of the population to be served. Examination of available demographic and epidemiologic data is one early step in this process. However, aggregate data for the entire geographic area of concern often fail to reveal important differences among geographically defined sub-populations--differences that influence the form an effective delivery system should take. We present a methodology based on exploratory data analysis (EDA) techniques that we have found useful in examining health-related data for our ambulatory care catchment area. Our examples use three population characteristics that have major implications for health care planning for the elderly: 1970-1980 change in population aged 65+; the percent of the population aged 65+ below poverty level; and the percent of single-person households among households with one or more persons aged 65+. With these data for the 25 municipalities of Middlesex County, New Jersey, we illustrate a two-step process: (1) the construction of stem-and-leaf displays that permit examination of a data distribution for asymmetry, concentrations around specific values, gaps in values, and outliers; and (2) the use of the median, the fourth-spread, and other information from the stem-and-leaf display in the systematic selection of data value classes to be given distinct shadings on a map of the selected geographic area. Discussion emphasizes the usefulness of graphic display of data in detecting similarities and unusual data values. Comparison of maps based on the EDA techniques and maps based on several traditional methods of value classing for the same data illustrates the influence of classing choices on the interpretation of cartographic displays of health-related data.
US asthma mortality rates have been increasing during the past 10 years. Little is known about the geographic variation of this infrequent health event. Using US vital records for the 1981-1985 period, small-area variation of excess asthma mortality of young adults was studied. Several geopolitical definitions were used to define populations. A total of 22 single counties, 12 metropolitan statistical areas, 11 health service areas, and 29 state economic areas were identified as having mortality significantly in excess of that expected, based on US race/sex-specific rates. Significant variation in asthma mortality was found at several levels of geopolitical classification of the data. Elevated areas included the central plains states and three large urban metropolitan areas--Chicago, Illinois, New York, New York, and Phoenix, Arizona--as well as a few mostly suburban populations. Areas with excess mortality may provide a useful population base for further epidemiologic investigation into the risk factors associated with the more frequent morbid events of this disease, such as emergency room and hospital utilization.