PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Demographic modelling”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 289 records · Page 16Linked to original sources
PubMed2004

Precision and accuracy of divergence time estimates from STR and SNPSTR variation.

Inference of intraspecific population divergence patterns typically requires genetic data for molecular markers with relatively high mutation rates. Microsatellites, or short tandem repeat (STR) polymorphisms, have proven informative in many such investigations. These markers are characterized, however, by high levels of homoplasy and varying mutational properties, often leading to inaccurate inference of population divergence. A SNPSTR is a genetic system that consists of an STR polymorphism closely linked (typically < 500 bp) to one or more single-nucleotide polymorphisms (SNPs). SNPSTR systems are characterized by lower levels of homoplasy than are STR loci. Divergence time estimates based on STR variation (on the derived SNP allele background) should, therefore, be more accurate and precise. We use coalescent-based simulations in the context of several models of demographic history to compare divergence time estimates based on SNPSTR haplotype frequencies and STR allele frequencies. We demonstrate that estimates of divergence time based on STR variation on the background of a derived SNP allele are more accurate (3% to 7% bias for SNPSTR versus 11% to 20% bias for STR) and more precise than STR-based estimates, conditional on a recent SNP mutation. These results hold even for models involving complex demographic scenarios with gene flow, population expansion, and population bottlenecks. Varying the timing of the mutation event generating the SNP revealed that estimates of divergence time are sensitive to SNP age, with more recent SNPs giving more accurate and precise estimates of divergence time. However, varying both mutational properties of STR loci and SNP age demonstrated that multiple independent SNPSTR systems provide less biased estimates of divergence time. Furthermore, the combination of estimates based separately on STR and SNPSTR variation provides insight into the age of the derived SNP alleles. In light of our simulations, we interpret estimates from data for human populations.

Data Interpretation, Statistical↗
PubMed2004

Projecting the demographic consequences of adult HIV prevalence trends: the Spectrum Projection Package.

This paper describes the software package Spectrum, which is a modular program that is used to examine the consequences of current trends and future program interventions in reproductive health. It is used to determine the consequences of the HIV/AIDS epidemic, including the number of people living with HIV/AIDS by age and sex, the number of AIDS deaths, and the number of orphans as a result of AIDS, as well as other demographic indicators of interest, such as life expectancy and <5 mortality. The core of Spectrum is a demographic projection model called DemProj, which projects the population by age and sex. Other modules interact with the demographic projection. The HIV/AIDS projections are added to the demographic projections using a module called AIDS Impact Model. This module uses the projection of adult HIV prevalence over time, which is prepared using the Estimation and Projection Package model or the projection workbook. It also requires assumptions about the epidemiology of HIV, including the ratio of female:male prevalence, the distribution of infection by age, the distribution of the time from infection until AIDS death, and the effect of HIV on fertility.

Acquired Immunodeficiency Syndrome↗
PubMed2003

Risk adjustment using automated ambulatory pharmacy data: the RxRisk model.

OBJECTIVES: Develop and estimate the RxRisk model, a risk assessment instrument that uses automated ambulatory pharmacy data to identify chronic conditions and predict future health care cost. The RxRisk model's performance in predicting cost is compared with a demographic-only model, the Ambulatory Clinical Groups (ACG), and Hierarchical Coexisting Conditions (HCC) ICD-9-CM diagnosis-based risk assessment instruments. Each model's power to forecast health care resource use is assessed. DATA SOURCES: Health services utilization and cost data for approximately 1.5 million individuals enrolled in five mixed-model Health Maintenance Organizations (HMOs) from different regions in the United States. STUDY DESIGN: Retrospective cohort study using automated managed care data. SUBJECTS All persons enrolled during 1995 and 1996 in Group Health Cooperative of Puget Sound, HealthPartners of Minnesota and the Colorado, Ohio and Northeast Regions of Kaiser-Permanente. MEASURES RxRisk, an algorithm that classifies prescription drug fills into chronic disease classes for adults and children. RESULTS: HCCs produce the most accurate forecasts of total costs than either RxRisk or ACGs but RxRisk performs similarly to ACGs. Using the R(2) criteria HCCs explain 15.4% of the prospective variance in cost, whereas RxRisk explains 8.7% and ACGs explain 10.2%. However, for key segments of the cost distribution the differences in forecasting power among HCCs, RxRisk, and ACGs are less obvious, with all three models generating similar predictions for the middle 60% of the cost distribution. CONCLUSIONS: HCCs produce more accurate forecasts of total cost, but the pharmacy-based RxRisk is an alternative risk assessment instrument to several diagnostic based models and depending on the nature of the application may be a more appropriate option for medical risk analysis.

Adolescent↗
PubMed2006

Combined CD4/CD8 ratio in induced sputum and pulmonary function testing for non-invasive identification of sarcoidosis.

UNLABELLED: Induced sputum is a useful noninvasive method for assessing parenchymal diseases. This retrospective study investigated its potential application in combination with functional parameters to differentiate sarcoidosis from non-sarcoid interstitial lung disease (NSA-ILD), especially when bronchoscopy is clinically contraindicated. All 120 study patients (67 sarcoidosis and 53 NSA-ILD) underwent both bronchoalveolar lavage (flexible fiberoptic video bronchoscope; Pentax, Japan) and induced sputum testing (3% NaCl, selecting plugs method, 300 cells differentially counted in Giemsa stained cytopreps). CD4/CD8 subsets were identified by a fluorescence-activator cell sorter. All patients underwent high-resolution computerized tomography and 103 of 120 underwent transbronchial biopsy. Multivariate logistic regression models were applied to the data to predict the probability of having the sarcoidosis as a function of the explanatory variables: Model I contained demographic and induced sputum data, and Model II included demographic data and combined sputum and pulmonary function test results. The area under the curve was 0.899 for induced sputum parameters alone and 0.914 for induced sputum and pulmonary function parameters. CONCLUSION: The results derived from the combination of noninvasive induced sputum approach can be used as predictors with high specificity and sensitivity in the differential diagnosis of sarcoidosis.

Adult↗
PubMed2005

Relationship of validated psychometric tools to subsequent medical utilization for asthma.

BACKGROUND: Risk stratification is used to identify patients with asthma at increased risk of experiencing morbidity and resource utilization. Validated psychometric tools are infrequently studied sources of data for this purpose. PURPOSE: To evaluate 4 types of validated psychometric tools as predictors for subsequent asthma utilization and determine their clinical usefulness. METHODS: Eleven hundred patients with active asthma from a Health Maintenance Organization completed surveys that included demographic information and validated psychometric tools measuring generic quality of life (physical and mental components), asthma-specific quality of life, asthma control, and asthma symptom severity. Survey records were linked to administrative data that captured emergency department and hospital care, short-acting beta-agonist, and oral corticosteroid utilization for the year of and the year following the survey. Relationships of survey variables with subsequent utilization were assessed, adjusting for both baseline demographic and asthma utilization factors. RESULTS: Scores of each psychometric tool were significantly related to subsequent utilization in univariate analyses and after adjusting for baseline utilization and demographic risk factors. Patients with higher scale-defined morbidity were as much as 4 times more likely to have subsequent utilization (sensitivity as high as 58%; specificity as high as 78%). Addition of an asthma-specific tool to either demographic or utilization prediction models added sensitivity (as much as 15%) but did not substantially improve the prediction properties of models containing both demographic and utilization predictors. CONCLUSION: Validated psychometric tools appear useful for asthma risk stratification in individuals and in populations in which both utilization and demographic predictors are not available.

Adolescent↗
PubMed1997

Using the 1991 Census SAR in a multilevel analysis of male unemployment.

"The Sample of Anonymised Records drawn from the 1991 [United Kingdom] Census is used to model geographical, demographic, and socioeconomic variations in male unemployment by means of multilevel logit models. The underlying structure of the problem is such that cells in a multiway cross-tabulation of individual characteristics (level 1) are nested within places (level 2). Geographical variations in male unemployment are found even after allowing for age, marital status, ethnicity, higher education qualifications, social class, and industry."

Developed Countries↗
PubMed2006

Lower-than-expected prevalence and severity of retinopathy in an incident cohort followed during the first 4-14 years of type 1 diabetes: the Wisconsin Diabetes Registry Study.

The authors examined the development of diabetic retinopathy in a population-based cohort of persons with incident type 1 diabetes to investigate the possibility of lowered retinopathy prevalence and severity compared with previous US studies. A total of 474 diabetic persons from Wisconsin were followed from diagnosis through 4-14 years' duration during 1990-2002. Retinopathy was determined by fundus photography at 4, 7, 9, and 14 years' duration. Risk of developing retinopathy was modeled on demographic and diabetes-care characteristics by means of a generalized linear model using the complementary log-log link for interval-censored data. Prevalence of retinopathy increased with duration of diabetes, from 6% at 4 years to 73% at 14 years, and was highest among adults (> or =20 years of age). Risk of developing retinopathy increased with increasing duration, worse glycemic control, and age up to 20 years. Indicators of diabetes care were related to retinopathy through their effect on glycemic control. Improvements in diabetes care leading to better glycemic control may have contributed to the much lower prevalence and less severe retinopathy observed than expected on the basis of a previous report from the same region of Wisconsin. The observed decreased prevalence has important implications for persons with type 1 diabetes, since retinopathy is a serious microvascular complication.

Adolescent↗
PubMed2005

Bayesian coalescent inference of past population dynamics from molecular sequences.

We introduce the Bayesian skyline plot, a new method for estimating past population dynamics through time from a sample of molecular sequences without dependence on a prespecified parametric model of demographic history. We describe a Markov chain Monte Carlo sampling procedure that efficiently samples a variant of the generalized skyline plot, given sequence data, and combines these plots to generate a posterior distribution of effective population size through time. We apply the Bayesian skyline plot to simulated data sets and show that it correctly reconstructs demographic history under canonical scenarios. Finally, we compare the Bayesian skyline plot model to previous coalescent approaches by analyzing two real data sets (hepatitis C virus in Egypt and mitochondrial DNA of Beringian bison) that have been previously investigated using alternative coalescent methods. In the bison analysis, we detect a severe but previously unrecognized bottleneck, estimated to have occurred 10,000 radiocarbon years ago, which coincides with both the earliest undisputed record of large numbers of humans in Alaska and the megafaunal extinctions in North America at the beginning of the Holocene.

Algorithms↗
PubMed2001

Satisfaction with innovative community and university health clinic programs for groups of traditionally underserved individuals with HIV/AIDS: empirical models.

As the demographics of the populations of affected individuals have changed, systems of care have needed to adapt to be responsive to client needs. This article examines client satisfaction data from seven national demonstration projects funded to enroll individuals from traditionally underserved groups and help them access services using different strategies. Data on client satisfaction ratings were related to indicators of traditionally underserved status, including demographic characteristics, behaviors, and other risk factors using the data modeling method of Exhaustive CHAID (Chi-squared Automatic Interaction Detector). Client groups that were most likely to experience relatively higher and lower levels of satisfaction with services are identified. Overall, all client groups were highly satisfied with the innovative HIV/AIDS services received. The findings illustrate the success of these innovative HIV care models in being responsive and sensitive to the needs of their target populations.

Adult↗
PubMed2000

Health-risk-assessment tools used to predict costs in defined populations.

With the Balanced Budget Act of 1997 mandating that the Health Care Financing Administration (HCFA) implement risk-adjusted payment mechanisms for Medicare managed care plans (Medicare + Choice) by January 2000, risk-adjustment tools will play an important role in future capitated reimbursement. This is because there is growing evidence that healthier-than-average beneficiaries select Medicare + Choice. The risk adjustment that HCFA has adopted is initially based on primary inpatient diagnosis from hospitalizations in the previous year. Other payers are likely to adopt similar payment mechanisms. This article reviews nineteen risk-adjustment research papers, including the tool adopted for Medicare + Choice, some of which are likely to form the basis for subsequent HCFA risk-adjustment methods. In general, claims-based models are more powerful in predicting total costs than survey-based or demographics-based models. Survey-based models, although expensive and not as powerful claims-based models, can be used when claims data are unavailable. One of the most popular survey-based tools, SF-36, is likely to become increasingly important because HCFA will be using it to measure quality outcomes from Medicare + Choice plans and will make the results public. All of the models reviewed have limitations, but can be expected to be building blocks for future risk-based capitated reimbursement.

Aged↗
PubMed1996

[Development of dementia to the year 2050. Model calculations for Germany with special reference to future mortality progress].

On the basis of existing age structures of the demented, a demographic-epidemiological model (DEPOP) is used to project the number of demented to the year 2050 in Germany. In particular a future progress in survivorship of the oldest is assumed in the simulation run in continuation of the already visible path of demographic aging. Taking future mortality reductions into calculation the total number of the demented population will increase at least threefold. Together with the stagnation or decline of the total population, this signifies a considerable increase in the relative importance dementia results.

Aged↗
PubMed1999

Prognostic factors for short-term survival in patients with stage IV non-small cell lung cancer.

Prognostic factors which can forecast short-term survival in patients with stage IV non-small cell lung cancer have not been well evaluated. Characteristics of such factors may be different from those for overall survival, and would be an important eligibility criterion for clinical trials of chemotherapy. We retrospectively analyzed the data of 158 patients with stage IV non-small cell lung cancer whose performance status was 0, 1 or 2. Univariate and multivariate logistic regression models revealed demographic variables which significantly correlated with the survival at 8 or 12 weeks. The univariate model showed the following significant variables: T factor, N factor, number of organs with metastases, grade of performance status, weight loss within 6 months, evidence of metastasis either at bone or lymph node, and lactate dehydrogenase level. The subsequent multivariate model demonstrated that both grade of performance status under 2 and number of metastasized organs less than 3 are important factors for 8- or 12-week survival. The survival rate in patients meeting the two criteria (grade of performance status under 2 and number of metastasized organs less than 3) and in those meeting only one of them was 93% versus 80% at 8 weeks (P = 0.030) and 88% versus 62% at 12 weeks (P < 0.001), respectively. Grade of performance status and number of organs with metastases appear to be important prognostic factors for short-term survival in patients with stage IV non-small cell lung cancer.

Adult↗
PubMed1991

[Life-style and demographic behavior: an application of latent class analysis].

"The aim of this study is to construct a lifestyle typology which is relevant for demographic behaviour. The concept lifestyle is defined as attitudes towards marriage, family, parenthood and the labour force participation of women. The lifestyle indicators available in the 1988 Netherlands Fertility Survey are used to construct a typology by means of latent-class-models.... The lifestyle typology can be used in two ways for projection purposes. Firstly, it can be as an explanatory variable in models for demographic behaviour. This application is demonstrated with a discrete-time hazard model for first births....Secondly, it can be used to identify innovators with respect to demographic behaviour and to quantify alternative hypotheses about the number of followers. This is demonstrated by calculating the future proportion of childlessness." (SUMMARY IN ENG)

Attitude↗
PubMed1981

A framework for modeling interregional population distribution and economic growth.

"An integrated model is proposed to capture economic and demographic interactions in a system of regions. This model links the interregional economic model of Isard (1960) and the interregional demographic model of Rogers (1975) via functions describing consumption and migration patterns. Migration rates are determined jointly with labor force participation rates and unemployment rates."

Demography↗
PubMed1985

Demographic-economic analysis in a multi-zonal region: a case study of Nordrhein-Westfalen.

"This paper develops a series of spatially-disaggregated demographic-economic models, based on an extended Leontief type input-output model. Travel between residence and place of work and residence and place of shopping is included in the models, and a detailed decomposition of a range of multipliers identified. A model explicitly involving travel to work is developed empirically for the state of Nordrhein-Westfalen in West Germany, and sets of multipliers presented which relate changes in demographic and economic variables in particular zones of the state with changes in economic output and employment-related variables in other zones."

Behavior↗
PubMed2003

Statistical tests of demographic heterogeneity theories.

In this paper we develop predictions from models of life-long demographic heterogeneity. These predictions are then compared to observations of mortality in large laboratory populations of Drosophila melanogaster. We find that the demographic heterogeneity models either require levels of variation that far exceed what would be considered biologically plausible, or they predict a much larger number of very old individuals than we actually observe. We conclude that the demographic heterogeneity models are not reasonable explanations of demographic patterns and are weakly motivated biological models.

Aging↗
PubMed1992

[The demographic transition in Finland and Hungary].

"The study compares demographic transition in Finland and Hungary in the 1881-1986 period. The analysis focuses on the classical two-factor model of demographic transition, i.e. the effect of fertility and mortality on the number and age composition of inhabitants.... The author [also] presents six population projections, prepared with the [cohort] method, covering the period of 1991-2041. By means of these he compares the likely changes in the number and age composition of inhabitants in Finland and Hungary." (SUMMARY IN ENG AND RUS)

Age Distribution↗