Economic determinants of fertility: results from cross-sectional aggregate data.
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Adult↗
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Results for “Data Aggregation”
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On the accommodation of disease rate correlations in aggregate data studies of disease risk factors.
Prentice and Sheppard (1995, Biometrika 82, 113-125) proposed a method for estimating relative risks associated with poorly measured exposures using disease rates from multiple populations and exposure and confounding factor data from sample surveys of persons in each population. The method involved an assumption of independence of disease rates across populations, conditional on exposures and confounding factors. Here, this assumption is relaxed by allowing dependencies among the disease rates within a partition of the populations, perhaps defined on the basis of geographic proximity or cultural similarity. Such dependencies could, for example, derive from unmeasured risk factors that are shared among neighboring populations. Dependencies within an element of the partition are modeled by allowing a common correlation between the disease rates of contiguous populations and by inducing correlations between the rates for noncontiguous populations using a multivariate lognormal assumption. Estimating equations are proposed for relative risk parameter estimation, and robustness and efficiency properties are assessed through simulations. The relaxed estimation procedure is shown to yield useful efficiency gains when moderate or strong disease rate dependencies are present, especially when disease rate variances are large relative to binomial variance.
Aged↗
Reliability of aggregated organizational data: an evaluation of five empirical indices.
Nursing systems research has included many levels of measurement such as individuals, work groups, organizations, and systems of organizations. Variables important to organizational survival often are measured at the individual level, with inferences made to the work group or the organization. This study demonstrated a process for determining the reliability of individual level data aggregated to the work group and organization levels. Data were analyzed on four variables: job enjoyment; manager's leadership style in terms of structuring expectations and consideration; and control over nursing practice. Job enjoyment was assessed over time. Registered staff nurses (n = 632), representing 54 nursing units from 4 large acute care hospitals, comprised the sample. The results indicated the assessment of reliability and validity is important at the level of inference and at each time interval. Aggregated data were deemed reliable when the following criteria were met: Cronbach's alpha > .60; intraclass correlation (1,k) > .60; and a significant F ratio. The interpretation of omega 2 as an indicator of effect size suggested that the validity of inference at the aggregated level is in question when effect size is negligible or small.
Data Interpretation, Statistical↗
Secondary data bases and their use in outcomes research: a review of the area resource file and the Healthcare Cost and Utilization Project.
Secondary data sources are being used more frequently than ever in outcomes research. The speed and relative low cost of these data bases makes them ideal for analyzing outcomes. Today's researcher has numerous secondary data bases available for use. Few publications exist to help researchers locate the ideal data set for their needs. Herein, two national secondary data bases are reviewed: the Area Resource File (ARF) and the Healthcare Cost and Utilization Project (HCUP). These two data sets represent the two types of secondary data: aggregate and individual. ARF represents an aggregate data set and HCUP represents an individual data set. The advantages of each type of secondary data will also be reviewed.
Centers for Medicare and Medicaid Services, U.S.↗
Improving environmental exposure analysis using cumulative distribution functions and individual geocoding.
BACKGROUND: Assessments of environmental exposure and health risks that utilize Geographic Information Systems (GIS) often make simplifying assumptions when using: (a) one or more discrete buffer distances to define the spatial extent of impacted regions, and (b) aggregated demographic data at the level of census enumeration units to derive the characteristics of the potentially exposed population. A case-study of school children in Orange County, Florida, is used to demonstrate how these limitations can be overcome by the application of cumulative distribution functions (CDFs) and individual geocoded locations. Exposure potential for 159,923 school children was determined at the childrens' home residences and at school locations by determining the distance to the nearest gasoline station, stationary air pollution source, and industrial facility listed in the Toxic Release Inventory (TRI). Errors and biases introduced by the use of discrete buffer distances and data aggregation were examined. RESULTS: The use of discrete buffers distances in proximity-based exposure analysis introduced substantial bias in terms of determining the potentially exposed population, and the results are strongly dependent on the choice of buffer distance(s). Comparisons of exposure potential between home and school locations indicated that different buffer distances yield different results and contradictory conclusions. The use of a CDF provided a much more meaningful representation and is not based on the a-priori assumption that any particular distance is more relevant than another. The use of individual geocoded locations also provided a more accurate characterization of the exposed population and allowed for more reliable comparisons among sub-groups. In the comparison of children's home residences and school locations, the use of data aggregated at the census block group and tract level introduced variability as well as bias, leading to incorrect conclusions as to whether exposure potential was higher at school or at home. CONCLUSION: The use of CDFs in distance-based environmental exposure assessment provides more robust results than the use of discrete buffer distances. Unless specific circumstances warrant the use of discrete buffer distances, their applcation should be discouraged in favor of CDFs. The use of aggregated data at the census tract or block group level introduces substantial bias in environmental exposure assessment, which can be reduced through individual geocoding. The use of aggregation should be minimized when individual-level data are available. Existing GIS analysis techniques are well suited to determine CDFs as well as reliably geocode large datasets, and computational issues do not present a barrier for their more widespread use in environmental exposure and risk assessment.
Child↗
On ecological fallacy, assessment errors stemming from misguided variable selection, and the effect of aggregation on the outcome of epidemiological study.
In social and environmental sciences, ecological fallacy is an incorrect assumption about an individual based on aggregate data for a group. In the present study, the validity of this assumption was tested using both individual estimates of exposure to air pollution and aggregate data for 1,492 schoolchildren living in the in vicinity of a major coal-fired power station in the Hadera region of Israel. In 1996 and 1999, the children underwent subsequent pulmonary function tests (PFT), and their parents completed a detailed questionnaire on their health status and housing conditions. The association between children's PFT results and their exposure to air pollution was investigated in two phases. During the first phase, PFT averages were compared with average levels of air pollution detected in townships, and small census areas in which the children reside. During the second phase, individual pollution estimates were compared with individual PFT results, and pattern detection techniques (Getis-Ord statistic) were used to investigate the spatial data structure. While different levels of areal data aggregation changed the results only marginally, the choice of indices measuring the children's PFT performance had a significant influence on the outcome of the analysis. As argued, differences between individual-level and group-level effects of exposure (i.e., ecological or cross-level bias) are not necessary outcomes of data aggregation, and that seemingly unexpected results may often stem from a misguided selection of variables chosen to measure health effects. The implications of the results of the analysis for epidemiological studies are discussed, and recommendations for public health policy are formulated.
Child↗
Issues regarding aggregation of data in nursing systems research.
The unit of analysis at which variables are conceptualized and measured is an important consideration when conducting patient outcomes research. Outcomes research ranges from study of individual responses to nursing intervention to investigation of group level outcomes associated with the contexts and processes through which nursing care is delivered. Because many variables salient to the investigation of group level patient outcomes are not amenable to direct measurement, aggregation procedures are used to generate proxy measurement of organizational context or process variables. In this article, key conceptual and methodologic issues encountered when using data aggregation procedures are reviewed. Following this, estimation of aggregated data reliability is illustrated using data from a study conducted to investigate skilled nursing unit structures.
Data Interpretation, Statistical↗
[Induced cell aggregation].
Data from literature concerning cell aggregation induced by various substances are considered. The biochemical nature of cell aggregation inducers, participation of membrane receptors in this process, biochemical aspects and practical significance of the cell aggregation process are discussed.
Animals↗
[Effect of clopheline on thrombocyte aggregation].
Data on clopheline effect on platelet aggregation, both spontaneous and ADP- or adrenaline-induced, in normal donors are reported. Clopheline is shown to slightly increase aggregation in normal subjects, exhibiting properties of a weak aggregation inductor. Where adrenaline is present in the aggregating system, clopheline undermines its platelet aggregation-inducing effect and, consequently, shows properties of a more competitive antagonist, as compared to adrenaline.
Adrenergic alpha-Agonists↗
Epidemiology of child pedestrian casualty rates: can we assume spatial independence?
Child pedestrian injuries are often investigated by means of ecological studies, yet are clearly part of a complex spatial phenomena. Spatial dependence within such ecological analyses have rarely been assessed, yet the validity of basic statistical techniques rely on a number of independence assumptions. Recent work from Canada has highlighted the potential for modelling spatial dependence within data that was aggregated in terms of the number of road casualties who were resident in a given geographical area. Other jurisdictions aggregate data in terms of the number of casualties in the geographical area in which the collision took place. This paper contrasts child pedestrian casualty data from Devon County UK, which has been aggregated by both methods. A simple ecological model, with minimally useful covaraties relating to measures of child deprivation, provides evidence that data aggregated in terms of the casualty's home location cannot be assumed to be spatially independent and that for analysis of these data to be valid there must be some accounting for spatial auto-correlation within the model structure. Conversely, data aggregated in terms of the collision location (as is usual in the UK) was found to be spatially independent. Whilst the spatial model is clearly more complex it provided a superior fit to that seen with either collision aggregated or non-spatial models. Of more importance, the ecological level association between deprivation and casualty rate is much lower once the spatial structure is accounted for, highlighting the importance using appropriately structured models.
Accidents, Traffic↗
Trends in treatment of localized prostate cancer by radical prostatectomy: observations from the Commission on Cancer National Cancer Database, 1985-1990.
OBJECTIVE: Tumor registry data were studied to assess the magnitude and nature of the trend toward increased use of radical prostatectomy for the treatment of newly diagnosed localized prostate cancer. METHODS: The Commission on Cancer of the American College of Surgeons National Cancer Data Base aggregates data from hospital tumor registries located throughout the United States. Data from this resource on 4,531 patients treated in 1985, 25,028 treated in 1988, and 21,697 treated in 1990 were reviewed. RESULTS: The data indicate that selection of radical prostatectomy increased markedly over this interval. Use of radical prostatectomy was greatest in younger men in every year studied. The proportion of patients treated by radical prostatectomy was greatest in the western United States and least in New England and the mid-Atlantic region. Radical prostatectomy was associated with patients' socioeconomic status and race as well as with the hospital's caseload of patients with cancer. CONCLUSIONS: The pattern of care for localized prostate cancer is changing significantly. Further research is needed to assess whether these variations reflect differences in access to care or patterns of patient preference.
Aged↗
Adolescent pregnancy-prevention program. A model for research and evaluation.
Despite the increased interest in the effects of adolescent pregnancy-prevention programs, most interventions lack the research design and data essential for evaluation. This article describes a model in which evaluative research was incorporated in program design. The derivation of the model, the selection of measurable parameters, characteristics of the population reflected in baseline and subsequent data, and problems in quantifying and interpreting appropriate variables are discussed. Clinic data and aggregate data from three self-administered surveys is used. The surveys were completed by students in the inner-city junior and senior high schools that cooperated in the education and clinical program. We demonstrate how these two types of data augment one another in assessing program effects. The study explores the evaluation and the timing of change in sexual knowledge, attitudes, and behavior (coital, contraceptive, and clinic) and thus may contribute to the design of measurable, replicable interventions.
Adolescent↗
Impact of quality improvement activities on care for acute myocardial infarction.
OBJECTIVE: To examine the relationship between quality improvement activities reported to a peer review organization (PRO) and improvements in quality of care for patients with acute myocardial infarction (AMI). DESIGN: Time-series, comparative study of changes in care for AMI patients from 1992 to 1995 in hospitals reporting self-measurement or system changes compared to all other hospitals in the state. SETTING: One-hundred and seventeen acute care hospitals in Iowa. STUDY PARTICIPANTS: Patients hospitalized with a principal diagnosis of AMI. INTERVENTIONS: Each hospital was given hospital-specific performance data, statewide aggregate data, and peer comparisons and was asked to provide the PRO with a plan to improve care for AMI patients. MEASUREMENTS: Chart audits were performed before and after the intervention. Quality of care was based on eight explicit process measures of the quality of AMI care (quality indicators). RESULTS: Statewide, quality of care improved on five out of eight quality indicators. Of the 117 hospitals, 44 (38%) reported that they had implemented their own measurement activities or systematic improvements. These 44 hospitals showed significantly greater improvements than the other hospitals in use of aspirin during the hospitalization, recommendations for aspirin at discharge, and prescriptions for beta blockers at discharge. CONCLUSIONS: While quality of care for AMI patients throughout Iowa is improving, the pace of improvement is greatest in hospitals reporting that they are measuring their own performance or implementing systematic changes in care processes. Continued efforts to encourage hospitals to implement these types of improvement activities are warranted.
Cardiology Service, Hospital↗
Can a public health care system achieve equity? The Norwegian experience.
Equity in health care provision is an important policy goal in Norway. This article addresses equality in the services provided by primary care physicians. These services are the responsibility of local government financed mainly through public funding. Patient fees are low. The local government system results in geographical variation in the number of physicians relative to local health demands. The authors present the hypothesis that this generates inequalities in health care utilization. The system of government finance is based on the assumption that utilization of health services is independent of patient income. Therefore, variation in income is expected to have only a small impact on utilization. The authors estimate a demand model by combining extensive micro data with aggregate data on municipal supply. There is very little relationship between indicators of access and health care utilization. The estimated income elasticities approximate zero, supporting the argument that equality in utilization has been achieved. However, the authors results also raise the question of whether equality has been achieved at the cost of limiting supply of services for people who could afford to consume more, or to pay for services of higher quality.
Adolescent↗
Using data for couples to project the distributional effects of changes in Social Security policy.
Under Social Security program rules, the aged receive Social Security benefits either as retired workers, spouses, divorced spouses, or widow(er)s. Retired-worker benefits are paid to workers who have 40 quarters of coverage over their lives. Auxiliary benefits are paid to spouses, divorced spouses, and widow(er)s of retired workers. Spouse benefits are computed using the earnings history of the current spouse for individuals who are married when they apply for benefits. Divorced spouse and widow(er) benefits are computed using the earnings history of the ex-spouse or deceased spouse with the highest PIA. A large number of retired women are entitled to auxiliary benefits. Some women receive only auxiliary benefits, while the majority of women have their retired-worker benefit supplemented by auxiliary benefits. Because the level of Social Security benefits can reflect the relative lifetime earnings of both spouses, as a couple, using individual data to estimate Social Security benefits will tend to underestimate actual benefits, particularly for women. However, detailed data for couples are often difficult to obtain. There is currently no known single data source that includes both marital and earnings history information. As a result, many researchers resort to estimating Social Security benefits using individual data or aggregate data, such as the average earnings of men and women. The Social Security Administration's Office of Research, Evaluation, and Statistics, with substantial assistance from the Brookings Institution, the Urban Institute, and the RAND Corporation, is developing a model that overcomes this problem by using the marital and earnings histories of both marital partners to estimate Social Security benefits. The Modeling Income in the Near Term (MINT) model projects retirement income (Social Security benefits, pension income, asset income, and earnings of working beneficiaries) from 1997 through 2031 for current and future Social Security beneficiaries using a unique data source--the Survey of Income and Program Participation (SIPP)--matched to Social Security Administration records. Using MINT data, this article establishes the importance of using data for couples rather than individuals by examining the impact of changing Social Security benefits to reflect 40 years of lifetime earnings rather than the 35 years required under current law. We compare the effect of this policy change on married women by estimating their benefits with data for couples and with individual data. Results indicate that: Using individual data overestimates the projected reduction in retirement benefits brought about by the policy change and makes the effects on women look more severe than they actually are. Because older birth cohorts are more likely than younger cohorts to receive auxiliary benefits based on their husbands' average lifetime earnings, the bias created by using individual data is projected to be much larger for older cohorts than for younger cohorts. This article emphasizes the importance of using data for couples to estimate Social Security benefits, particularly for women. Although our focus is on married women, using data for couples is just as important for calculating the retirement benefits of divorced and widowed individuals. For individuals who are divorced or widowed at retirement, their Social Security benefits are based on their own earnings history, as well as the earnings histories of each of their previous spouses.
Age Factors↗
Data collection in the Great Plains Genetics Service Network: using limited funds to collect data from centers with varying resources.
The Data Committee of the Great Plains Genetics Service Network (GPGSN) coordinates the collection of data relating to delivery of genetic services in eight states. These states are Iowa, Missouri, Arkansas, Oklahoma, Kansas, Nebraska, South Dakota and North Dakota. The funds allocated to this project by the GPGSN are limited. The distance between genetics service sites is great and the population density in the regions being served is low. The local resources available to the genetics services sites participating in data collection vary from robust to "bare-bones". The approach to solving the problem involved the following. First the committee the data items to be collected were identified and defined. Second, a standard format for transmitting the data to the GPGSN regional coordinating center in Iowa City was developed. Third, the services sites and their resources for collecting data were identified. Fourth, resources were allocated to different sites in a manner that seemed most able to help that center to contribute data to the regional center. Fifth, data were aggregated at the regional center and aggregated data reports were returned to collecting sites. Finally, items were modified in response to the feedback received from the genetics services sites. Although the philosophy is that data collection should be a by-product of providing quality genetic services, the region recognizes that service sites will need help to conform with regional standards. Therefore the region encourages each service site to develop its own method to collect data, and provides assistance to it in getting the data into the regional transmission format.(ABSTRACT TRUNCATED AT 250 WORDS)
Data Collection↗
Cardiovascular disease risk factors, CHD morbidity and mortality in the Federal Republic of Germany.
Analyses of data from the first National Health Examination Survey undertaken from 1984-1986 within the framework of the German Cardiovascular Prevention Study, show the following risk factor prevalences in 25-69 year-old men and women: overweight (BMI males: greater than 25, females greater than 24) or obese (BMI greater than 30): men 65.0%, women 57.6%; total serum cholesterol (less than 5.17 mmol/dl): men 73.7%, women 74.0%; normal blood pressure (according to JNC definitions): men 45.0%, women 59.1%; hypertension according to WHO criteria: men 26.0%, women 21.1%; controlled hypertensives (WHO criteria): men 19.9%, women 33.9%; current smoking: men 40.8%, women 26.1%. For most of the cardiovascular risk factors there is a clear negative association between prevalence and length of school education. Three myocardial infarction (MI) registries (WHO MONICA Project) are operating in the Federal Republic of Germany. Incidence and case-fatality data are within comparable ranges. Coronary heart disease (CHD) mortality has been relatively stable in both sexes from 1970 to 1986 with a minor peak in 1976 and a slight downward trend since then. A study of the reliability of coding procedures in West German state statistical offices revealed major disagreements so that trends derived from national mortality data as aggregate data of the federal states might be spurious. An ecological correlation of regional smoking prevalences (1978) and regional CHD mortality rates (1977-9) showed significant coefficients in men, but not in women.
Adult↗
Patient records: from single events to elements for health planning.
Data collected in patient records are not only the kernel of a ward information system, but also the groundwork for planning and evaluating services in health care. The aim of this study was to analyze the problem of aggregate data generation starting from separate items in patient records. After describing the different uses of patient record data, we outline the process which generates aggregates data starting from individual records. This process leads to the definition of the "view on aggregation" as an intermediate step between patient records and aggregate data. A simplified schema is presented based on the Entity-Relationship model representing a conceptual model of the integration of aggregate data and patient record items. Finally, the role is discussed of automation in this process and the perspectives for its implementation.
Data Collection↗