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 343 records · Page 19Linked to original sources

PubMed2004

Factors predictive of outcome after use of the Ponseti method for the treatment of idiopathic clubfeet.

BACKGROUND: The nonoperative technique for the treatment of idiopathic congenital talipes equinovarus (clubfoot) described by Ponseti is a popular method, but it requires two to four years of orthotic management. The purpose of this study was to examine the patient characteristics and demographic factors related to the family that are predictive of recurrent foot deformities in patients treated with this method. METHODS: The cases of fifty-one consecutive infants with eighty-six idiopathic clubfeet treated with use of the Ponseti method were examined retrospectively. The patient characteristics at the time of presentation, such as the severity of the initial clubfoot deformity, previous treatment, and the age at the initiation of treatment, were examined with use of univariate logistic regression analysis modeling recurrence. Demographic data on the family, including annual income, highest level of education attained by the parents, and marital status, as well as parental reports of compliance with the use of the prescribed orthosis, were studied in relation to the risk of recurrence. RESULTS: The parents of twenty-one patients did not comply with the use of orthotics. Noncompliance was the factor most related to the risk of recurrence, with an odds ratio of 183 (p < 0.00001). Parental educational level (high-school education or less) also was a significant risk factor for recurrence (odds ratio = 10.7, p < 0.03). With the numbers available, no significant relationship was found between gender, race, parental marital status, source of medical insurance, or parental income and the risk of recurrence of the clubfoot deformity. In addition, the severity of the deformity, the age of the patient at the initiation of treatment, and previous treatment were not found to have a significant effect on the risk of recurrence. CONCLUSION: Noncompliance and the educational level of the parents (high-school education or less) are significant risk factors for the recurrence of clubfoot deformity after correction with the Ponseti method. The identification of patients who are at risk for recurrence may allow intervention to improve the compliance of the parents with regard to the use of orthotics, and, as a result, improve outcome. LEVEL OF EVIDENCE: Prognostic study, Level II-1 (retrospective study). See Instructions to Authors for a complete description of levels of evidence.

Achilles Tendon↗

PubMed2003

Demographic, intrinsic, and extrinsic factors associated with weapon carrying at school.

BACKGROUND: Recent incidents of school violence have heightened the need to identify societal, interpersonal, and adolescent characteristics that contribute to weapon carrying. OBJECTIVES: To assess the prevalence of weapon carrying at school and to determine associated risk factors for adolescent males and females. DESIGN: A cross-sectional study using the 1994-1995 National Longitudinal Study of Adolescent Health data. PARTICIPANTS: A nationally representative sample of 6504 adolescents and their parents. MAIN OUTCOME MEASURE: Whether adolescents have ever carried a weapon at school. STATISTICS: chi(2) Analyses and hierarchical regressions were done using SPSS (SPSS Inc, Chicago, Ill) and SUDAAN (Research Triangle Park, NC) software. Regression models included demographic, intrinsic, and extrinsic factors. RESULTS: Of the overall sample, 9.3% (n = 595) reported having carried a weapon at school. Of these, 77% were male (male vs female adjusted odds ratio [AOR], 3.1; 95% confidence interval [CI], 2.3-4.1). Substance use, school problems, perpetration of violence, and witnessing violence were significantly associated with weapon carrying for both males and females. However, for males, extrinsic factors were more important in mediating the effects of substance use and perpetration of physical violence on school weapon carrying, while intrinsic factors mediate these variables for females. CONCLUSION: These findings suggest that interventions for violence prevention for males and females need to be targeted toward different areas.

Adolescent↗

PubMedDate not supplied

A core group model for disease transmission.

Models for sexually transmitted diseases generally assume that the size of the core group is fixed. Publicly available information on disease prevalence may influence the recruitment of new susceptibles into highly sexually active populations. It is assumed that the recruitment rate into the core population is low while disease prevalence is high, core group members mix only with each other, disease levels outside the core are negligible, and some core group members reduce their risk through the use of a partially effective vaccine or prophylactics. A demographic-epidemic model is formulated in which the combined size of the core and non-core population is constant. A simpler version models the epidemic in an isolated core population of constant size under the influence of educational programs and measures that reduce susceptibility. The threshold condition for an endemic infection is determined. Backward bifurcations, multiple infective stationary states, and hysteresis phenomena can be observed even in the simplified version. Abrupt changes in disease prevalence levels may result from small changes in the disease management parameters and do not occur in the absence of such a program. The general conclusion is that partially effective vaccination or education programs may increase the total number of cases while decreasing the relative frequency of cases in the core group. The study throws some new light on the role of the reproduction number in connection with elimination attempts. It shows that although the reproduction number defines the threshold for the spread of the disease in a susceptible population, it is of limited value when elimination of an existing epidemic is planned.

Demography↗

PubMed2005

Racial variations in self-reported osteoarthritis symptom severity among veterans.

BACKGROUND AND AIMS: This study aimed at examining factors related to osteoarthritis (OA) symptom severity in African American and Caucasian veterans (n=202). METHODS: OA symptom severity (lower extremity pain, stiffness, and physical function) was measured by the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). We also examined whether racial differences existed when controlling for other important demographic and clinical variables, including age, gender, income, educational level, employment status, marital status, number of years with OA symptoms, location of arthritic joints (hip, knee, back, foot/ankle), use of exercise, and current use of OA medications. Lastly, we examined whether factors associated with self-reported OA symptom severity differed in African American and Caucasian veterans. RESULTS: The mean WOMAC score for African American veterans (on a scale of 0-96) was 54.6 (SD=17.2), and the mean score for Caucasian veterans was 48.4 (SD=17.6; p=0.02). In a multivariable regression model including demographic and clinical variables, African American veterans had significantly higher WOMAC scores than Caucasians (3=0.185, p=0.009). In Caucasian veterans, greater number of years with OA, presence of hip OA, and a low income were associated with greater WOMAC scores. In African Americans, no use of exercise and the presence of OA in the hip or back were associated with greater WOMAC scores. CONCLUSIONS: Among this sample of veterans, African Americans had significantly higher WOMAC scores than Caucasians after controlling for other important demographic and clinical factors. Different and more intense treatment strategies may be needed for African American veterans with OA.

Black or African American↗

PubMed2006

Nemo: an evolutionary and population genetics programming framework.

UNLABELLED: Nemo is an individual-based, genetically explicit and stochastic population computer program for the simulation of population genetics and life-history trait evolution in a metapopulation context. It comes as both a C++ programming framework and an executable program file. Its object-oriented programming design gives it the flexibility and extensibility needed to implement a large variety of forward-time evolutionary models. It provides developers with abstract models allowing them to implement their own life-history traits and life-cycle events. Nemo offers a large panel of population models, from the Island model to lattice models with demographic or environmental stochasticity and a variety of already implemented traits (deleterious mutations, neutral markers and more), life-cycle events (mating, dispersal, aging, selection, etc.) and output operators for saving data and statistics. It runs on all major computer platforms including parallel computing environments. AVAILABILITY: The source code, binaries and documentation are available under the GNU General Public License at http://nemo2.sourceforge.net.

Biological Evolution↗

PubMed1990

Relationship of mood disorders to violence.

Past research on the relationship between mood disorders and violent behavior has been inconsistent, sometimes finding a relationship between the two and sometimes finding no relationship. Any relationship is arguably complex, and this area of research would benefit from attempts to clarify the relationship. This paper addresses the issue of complexity by examining the relationship between specific mood disorder categories and symptoms and six conceptually different indicators of violent behavior. Relationships are analyzed in logistic regression models where demographic and problem drinking variables are included to control variation that may be accounted for by these factors. The study uses a sample of 1140 recently incarcerated male felons. Psychiatric disorder diagnoses are based on the Diagnostic Interview Schedule. There is evidence of a direct relationship between a lifetime diagnosis of dysthymia and an arrest or incarceration history for robbery as well as with multiple incidents of fighting since age 18. Recurrent depression was significantly associated with a robbery incarceration history. Depression symptoms (regardless of whether a disorder diagnosis was made) were associated with multiple incidents of fighting since age 18. Manic symptoms were inconsistently associated with "expressive" violence and a number of mood disorder/violence models showed no significant relationship between the two.

Adult↗

PubMedDate not supplied

Metabolic control in non-insulin-dependent diabetes mellitus: factors associated with patient outcomes.

We conducted a cross-sectional study to assess the association of various demographic and medical-care variables with metabolic outcomes in non-insulin-dependent diabetic subjects. The study population was representative of the diagnosed care-seeking diabetic population of a defined geographic community on the Navajo reservation in Arizona. The dependent variable metabolic control was measured as the mean of all random plasma glucose values obtained only at scheduled diabetes clinic visits over 2 yr. Multivariate analysis of the data showed that better metabolic control was most strongly associated with compliance with scheduled appointments. Mode of treatment was also associated with metabolic control. Other variables tested, including source of care, age, sex, duration of diabetes, presence of complications, and weight change, were not associated with metabolic control. The strongest analysis of covariance model with demographic and medical-care variables accounted for 39% of the variance in metabolic control. The analysis suggests that other variables, possibly including several psychosocial variables, need to be assessed for their contribution to metabolic control.

Arizona↗

PubMed1990

The biodemography of variation in human frailty.

A population is composed of individuals who are heterogeneous in their susceptibility to death and disease. This heterogeneity is reflected in the age-specific incidence or mortality (hazard) function. This variation has typically been hidden--that is, not measured directly--and has generally been modeled in a purely empirical statistical way, because there is no theory in demography for the distribution of frailty. A substantial fraction of variation in frailty, however, has an underlying genetic basis, for which there is a formal theory. This theory, based on evolutionary biology and on the nature of mendelian transmission, provides prior constraints on the distribution of variation in the population as well as providing methods for identifying genes involved in many important diseases. The accumulating effects of environmental exposures with age are another major component of variation in frailty. In some important instances, this variation and its effect on the age-specific hazard function can also be understood in terms of cause-specific biological processes. These biological considerations may enable demographers to model frailty, and thus mortality, in a better way.

Disease Susceptibility↗

PubMed1987

Belorussia: the demographic transition and the settlement network in the 1980s.

Changes in the pattern of settlement in the Belorussian SSR, one of the constituent republics of the USSR, over the past 25 years is reviewed. The author suggests that Belorussia during this period has gone through the evolutionary process described in the demographic transition model. "The model outlines the changes in birth and death rates and their evolution over time in response to improved medical facilities, resulting in an increase of population of a region or country. At the same time the process of industrialization is accompanied by urbanization, which Belorussia has experienced in the period since 1959." A review of contemporary Soviet thinking on rural and urban settlement networks is included

Demography↗

PubMed2002

Effects of local interactions and local migration on stability.

Mathematical models can help to resolve the longstanding question of whether more diverse communities are more stable. Here, I focus on how local dispersal and local interactions--hallmarks of spatial communities--affect stability in a spatially implicit model with demographic stochasticity. The results are based on a novel way to analyze moment equations. The main conclusion is that the type and strength of density-dependent factors, such as fecundity and competition, determine whether local dispersal and local interactions increase or decrease stability. Local dispersal has a stabilizing effect when fecundity is high, interspecific competition is either low or high, and the number of species is small. Effects of local migration on stability are amplified when space is explicit.

Animal Migration↗

PubMed1988

The use of sigmoids in modelling and forecasting human populations.

"The aim of this paper is to present a review that might justify giving further consideration to the use of sigmoids in contemporary population modelling and forecasting. To do this a brief account is given of the historical development of these models, pointing out why demographers have viewed these trend models with scepticism. Most of the paper is devoted to showing that, despite these criticisms, sigmoid-based trend models are useful practical tools for the demographer." Examples using data for various countries are presented.

Demography↗

PubMed1993

Predictors of mortality in hemodialysis patients.

Serum biochemical measures suggestive of undernutrition have been reported to correlate with 1-yr mortality risk in prevalent groups of hemodialysis patients. The predictive power of these variables has not been reported in newly diagnosed patients or in patients whose dialysis prescription is guided by urea kinetics. The relationship of these predictors to mortality over periods of longer than 1 yr is also unreported. Therefore, the survival of 184 hemodialysis patients was examined for up to 44 months (1987 to 1991) with the Cox proportional hazards model. Baseline demographic, clinical, and biochemical parameters were used as independent variables. To adjust for bias in patient selection, the survival of patients with 12 months or less of prior dialysis at the time of enrollment ("new cases") was analyzed separately from that of patients with more than 1 yr of prior treatment ("long-standing cases"). Serum albumin was less than 3.5 g/dL in 31% of new cases and in 12% of long-standing cases. Adjusting for the other variables, low serum albumin was the strongest mortality risk predictor in both new and long-standing cases. Low serum cholesterol was an independent risk predictor in both groups. Diabetes and race were not significant predictors. Mean age at enrollment was nearly a decade higher for nonsurvivors than for survivors, in both new and long-standing groups. Yet, age was not an independent risk predictor in the Cox model for the new group because of an unexpectedly high death rate among young black men. Female gender, which was confounded by increased age, took the place of age in the model for the new group. For each model, there was good agreement between observed and predicted mortality for up to 24 months. To assess the influence of dialysis treatment time and dose (measured as pre-to-post treatment urea ratio) on risk, survival was examined in a subset of 139 patients monitored for up to 22 months, from 1989 to 1991, a period when the urea ratio was used routinely. Adjusting for the other variables, low serum albumin and cholesterol again independently increased risk. The urea ratio was also a significant independent predictor. The pattern of mortality by urea ratio was U shaped, with minimum risk for values between 2.5 and 3.4 Treatment time did not influence risk. It was concluded that baseline serum values of albumin and cholesterol strongly influence survival for up to 2 yr in new and long-standing hemodialysis patients.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗

PubMed2004

Pharmacy and medical claims data identified migraine sufferers with high specificity but modest sensitivity.

OBJECTIVE: Claims data are often used to identify and monitor individuals with particular conditions, but many health conditions are not easily recognizable from claims data alone. Patient characteristics routinely available in claims data were used to develop model-based claims signatures to identify migraineurs. STUDY DESIGN AND SETTING: A validated telephone interview was administered to 23,299 continuously enrolled managed care members aged 18-55 to identify 1,265 migraineurs and 1,178 controls. Responses were linked to medical and prescription claims. Claims variables were evaluated for sensitivity, specificity, and positive and negative predictive value in predicting migraine status. Regression models for predicting migraine status were developed. RESULTS: Regression-based claims signature models were successful in case-finding, as indicated by fairly sizable odds ratios (OR). In the full model (including demographic, medical, pharmacy, and comorbidity claims variables), a claim for a migraine drug, gender, and a claims-based headache diagnosis were strongly associated with migraine case status (OR=3.9, 3.2, and 3.0, respectively). CONCLUSION: Using either medical or pharmacy claims provided highly specific and moderately sensitive case-findings. Strategies that combined medical and pharmacy information improved sensitivity and may increase the usefulness of claims for identifying migraine and improving the quality of migraine care.

Adolescent↗

PubMed2006

The impact of increased environmental stochasticity due to climate change on the dynamics of asiatic wild ass.

Theory proposes that increased environmental stochasticity negatively impacts population viability. Thus, in addition to the directional changes predicted for weather parameters under global climate change (GCC), the increase in variance of these parameters may also have a negative effect on biodiversity. As a case study, we assessed the impact of interannual variance in precipitation on the viability of an Asiatic wild ass (Equus hemionus) population reintroduced in Makhtesh Ramon Nature Reserve, Israel. We monitored the population from 1985 to 1999 to determine what environmental factors affect reproductive success. Annual precipitation during the year before conception, drought conditions during gestation, and population size determined reproductive success. We used the parameters derived from this model to assess population performance under various scenarios in a Leslie matrix type model with demographic and environmental stochasticity. Specifically, we used a change in the precipitation regime in our study area to formulate a GCC scenario and compared the simulated dynamics of the population with a no-change scenario. The coefficient of variation in population size under the global change scenario was 30% higher than under the no-change scenario. Minor die-offs (> or = 15%) following droughts increased extinction probability nearly 10-fold. Our results support the idea that an increase in environmental stochasticity due to GCC may, in itself, pose a significant threat to biodiversity.

Animals↗

PubMed1975

REALPOP: a mathematical model for resource allocation in population programs-results from a test in the Dominican Republic.

The structure of a computerized mathematical model for resource allocation in population programs (REALPOP) and its application to the Dominican Republic's national family planning program are described. The model integrates demographic and management science approaches in the analysis of resource allocation, program planning, goal evaluation, and growth strategies of a family planning program. It is designed primarily to aid administrative decision-makers. The Dominican National Population and Family Council (NPFC) established a goal of reducing the crude birth rate from its 1968 level of 48 per thousand population to 28 per thousand in 15 years. Further, the program has established a clear set of program plans and alternatives. This study investigates the implication of these plans for the program's stated goals.

Contraceptives, Oral↗

PubMed2004

Cost containment analysis of childhood vaccination against varicella in Israel.

OBJECTIVES: The low cost of safe and effective vaccines prompted a cost-containment evaluation of a nationwide vaccination campaign against varicella. METHODS: A model incorporating demographic, epidemiologic and economic data from Israeli sources (supplemented by data from International literature) was constructed to estimate the decrease in morbidity and the consequent reductions in treatment costs and time-off work of a nationwide programme vaccinating children at 12 months. RESULTS: A policy of aiming to immunize a cohort of all 1-year-olds in Israel in the year 2002, for an annual cost of $1.10 million to the health services and $1.27 million to society (including lost work and transport costs), would reduce the number of cases of varicella during the lifetime of a cohort from 123,984 to 10,170 cases. This morbidity reduction would reduce national expenditures by $1.80 million in health service resources alone and by $24.5 million to society, mainly due to inaverted work absences. In addition an estimated 0.93 lives, representing 38.6 life years will be saved in the cohort. CONCLUSIONS: Under an assumption of neutrality relating to the potential effects of vaccination on herpes zoster virus, our model based calculations show that a national varicella vaccination programme is likely to be cost saving, not only from a societal perspective but also from the narrower health service perspective.

Chickenpox↗

PubMed1993

Numerical solution of structured population models. I. Age structure.

Numerical methods are presented for a general age-structured population model with demographic rates depending on age and the total population size. The accuracy of these methods is established by solving problems for which alternate solution techniques are available and are used for comparison. The methods reliably solve test problems with a variety of dynamic behavior. Simulations of a blowfly population exhibit cyclic fluctuations, whereas a simulated squirrel population reaches a stable age distribution and stable equilibrium population size. Life-history attributes are easily studied from the computed solutions, and are discussed for these examples. Recovery of a stressed population back to equilibrium is examined by computing the transition in age structure, and the transient behavior of other properties of the population such as the per capita growth rate, the average age, and the generation length.

Aging↗

PubMed2006

Household and community socioeconomic influences on early childhood malnutrition in Africa.

This paper uses multilevel modelling and Demographic and Health Survey data from five African countries to investigate the relative contributions of compositional and contextual effects of socioeconomic status and place of residence in perpetuating differences in the prevalence of malnutrition among children in Africa. It finds that community clustering of childhood malnutrition is accounted for by contextual effects over and above likely compositional effects, that urban-rural differentials are mainly explained by the socioeconomic status of communities and households, that childhood malnutrition occurs more frequently among children from poorer households and/or poorer communities and that living in deprived communities has an independent effect in some instances. This study also reveals that socioeconomic inequalities in childhood malnutrition are more pronounced in urban centres than in rural areas.

Africa↗