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Results for “Demographic modelling”

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PubMed1992

Health economic issues relevant to countries with aging populations.

This article investigates the health economic impacts of aging populations, using scenario techniques and economic systems analysis. Age-related data on hospital utilization and health care expenditure are linked with demographic models for Germany from 1990 to 2040. Findings indicate that the demographic component may not play a major role in determining long-term trends as compared with other, not yet fully elucidated components of utilization and expenditure, both of which are the result of the interplay between supply and demand in health care, and of interactions with the general economy. This acts as a deterrent against the use of simple extrapolations of current indicators (or their trends), but more adequate theoretical economic models are still lacking.

Adult↗

PubMed2006

Integrative models of bat rabies immunology, epizootiology and disease demography.

Bats are natural reservoirs of rabies. We address the maintenance of the disease in bat colonies by developing individual and population models that generate indicators of risk of rabies to bats, that provide dynamic estimates of effects of rabies on population densities, and that suggest consequences of viral exposures and infections in bats relative to physiological and ecological characteristics of bats in different habitats. We present individual models (within host) for the immune responses to a rabies virus challenge, an immunotypic disease model that describes the evolution of the disease and a disease demographics model, which is structured by immunotypic response governed by immune system efficiency. Model simulations are consistent with available data, characterized by relatively low prevalence of the virus in colonies and much higher prevalence of rabies virus-neutralizing antibodies. Under model conditions, there is a robust non-clinical state that can be attained by the exposed individual that allows persistence of the disease in the population.

Animals↗

PubMed1980

Population and agricultural development models: the promise of the third generation.

The author briefly describes the work of Malthus and the development of first- and second-generation economic-demographic models. He then discusses a proposed third-generation model which "examines conjointly both consequences and determinants of population growth, and analyzes them at the level of the agricultural household." A project being conducted by the Food and Agricultural Organization to construct a third-generation model using data from the Philippines and two other countries is described

Agriculture↗

PubMed2002

Mortality differences by APOE genotype estimated from demographic synthesis.

The 4 allele of apolipoprotein E (APOE) is associated with increased risk of two major causes of death in low-mortality populations: ischemic heart disease and Alzheimer's disease. It is less common among centenarians than at younger ages. Therefore, it is likely that it is associated with excess risk of death. This article extends demographic models that estimate relative mortality risks from changes in gene frequencies with age. The resulting demographic synthesis combines gene frequencies with data on mortality by genotype from cohort studies. The model was applied to data from Denmark, Finland, France, Italy, Sweden, and the United States. Near age 50, the 3/4 genotype is associated with a risk of death of 1.34 times that of the 3/3 (95% CI 1.18-1.67). The relative risk for 4/4 is the square of the relative risk for 3/4, 1.81. The 2/3 genotype is protective with a relative risk of 0.84 (0.68-0.93) near age 50. These relative risks move toward 1.0 at the oldest ages and APOE genotype is associated with little variation in mortality over age 100. There are no significant differences in the relative risks by sex. There is little evidence of differences within Europe in the effects of APOE. This approach can be generalized to combine data on genetic risk factors for disease from a wide variety of study designs and sample characteristics.

Age Factors↗

PubMed1994

Use effectiveness of the Creighton model ovulation method of natural family planning.

OBJECTIVE: To determine the use effectiveness of the Creighton model ovulation method in avoiding and achieving pregnancy. DESIGN: Prospective, descriptive. SETTING: A natural family planning clinic at a university nursing center. PARTICIPANTS: Records and charts from 242 couples who were taught the Creighton model. The sample represented 1,793 months of use of the model. MAIN OUTCOME MEASURE: Creighton model demographic forms and logbook. RESULTS: At 12 months of use, the Creighton model was 98.8% method effective and 98.0% use effective in avoiding pregnancy. It was 24.4% use effective in achieving pregnancy. The continuation rate for the sample at 12 months of use was 78.0%. CONCLUSION: The Creighton model is an effective method of family planning when used to avoid or achieve pregnancy. However, its effectiveness depends on its being taught by qualified teachers. The effectiveness rate of the Creighton model is based on the assumption that if couples knowingly use the female partner's days of fertility for genital intercourse, they are using the method to achieve pregnancy.

Adult↗

PubMed2003

Bayesian inferences on the recent island colonization history by the bird Zosterops lateralis lateralis.

The founding of new populations by small numbers of colonists has been considered a potentially important mechanism promoting evolutionary change in island populations. Colonizing species, such as members of the avian species complex Zosterops lateralis, have been used to support this idea. A large amount of background information on recent colonization history is available for one Zosterops subspecies, Z. lateralis lateralis, providing the opportunity to reconstruct the population dynamics of its colonization sequence. We used a Bayesian approach to combine historical and demographic information available on Z. l. lateralis with genotypic data from six microsatellite loci, and a rejection algorithm to make simultaneous inferences on the demographic parameters describing the recent colonization history of this subspecies in four southwest Pacific islands. Demographic models assuming mutation-drift equilibrium or a large number of founders were better supported than models assuming founder events for three of four recently colonized island populations. Posterior distributions of demographic parameters supported (i) a large stable effective population size of several thousands individuals with point estimates around 4000-5000; (ii) a founder event of very low intensity with a large effective number of founders around 150-200 individuals for each island in three of four islands, suggesting the colonization of those islands by one flock of large size or several flocks of average size; and (iii) a founder event of higher intensity on Norfolk Island with an effective number of founders around 20 individuals, suggesting colonization by a single flock of moderate size. Our inferences on demographic parameters, especially those on the number of founders, were relatively insensitive to the precise choice of prior distributions for microsatellite mutation processes and demographic parameters, suggesting that our analysis provides a robust description of the recent colonization history of the subspecies.

Bayes Theorem↗

PubMed2002

Utilization and cost of behavioral health services: employee characteristics and workplace health promotion.

The study sought to (1) model demographic and employment-related influences on behavioral health care utilization and cost; (2) model behavioral health care utilization and cost influences on general health care cost, job performance, and earnings; and (3) assess workplace-based health promotion's impact on these factors. Behavioral health care utilization was more common in employees who were female, over age 30, with below-median earnings, or with above-median general (non-behavioral) health care costs. Among employees utilizing behavioral health care, related costs were higher for employees with below-median earnings. Employees utilizing behavioral health care had higher general health care costs and received lower performance ratings than other employees. Health promotion participants were compared with a nonparticipant random sample matched on gender, age, and pre-intervention behavioral health care utilization. Among employees without pre-intervention behavioral health care, participants and nonparticipants did not differ in post-intervention utilization. Among employees utilizing behavioral health care adjusting for pre-intervention costs, participants had higher short-term post-intervention behavioral health care costs than nonparticipants.

Adolescent↗

PubMed1998

Consumerism as a branding opportunity.

Managing a customer portfolio at the individual level is the most difficult and most promising endeavor. An individual level consumer portfolio does not mean creating marketing materials and advertising campaigns customized for every member of your health plan. What it does mean is developing segmentation models based on consumer preferences extracted directly from your members, not socioeconomic or other demographic models. The most important information to extract is perceptions on how much and what kind of value members want from the organization.

Aged↗

PubMed2005

Pharmacy-and diagnosis-based risk adjustment for children with Medicaid.

BACKGROUND: Risk adjustment is useful for adjusting health care payments based on patients' health status. OBJECTIVE: This work seeks to examine how well pharmacy- and diagnosis-based risk adjusters predict child health expenditures in Medicaid populations. RESEARCH DESIGN: We used 1994-1995 Medicaid claims files for all children ages 0-18 years who were not covered by managed care in 3 states: Georgia, New Jersey, and Wisconsin. We examined separately 6 risk adjustment methods, 2 pharmacy-based and 4 diagnosis-based. We compared predictive accuracy of the methods for the whole sample and stratified by state and Medicaid enrollment category. FINDINGS: Models with risk adjustment (either diagnosis- or pharmacy-based) had better predictive accuracy than demographic models. The pharmacy and diagnosis-based models had similar predictive accuracy. Risk adjuster performance differed by Medicaid enrollment category and state. Risk-adjusted models generally underpredict expenditures in populations with worse health status (eg, those in the Supplemental Security Income program [SSI]). The pharmacy-based models performed well for children in SSI relative to children in foster care. CONCLUSIONS: Both pharmacy- and diagnosis-based risk adjustment improved the prediction of health expenditures compared models without risk adjustment. No single risk adjuster performed best in all situations, suggesting that optimal choices of risk adjusters may differ by purpose and context.

Adolescent↗

PubMed2006

Bioeconomic modeling in conservation pest management: effect of stoat control on extinction risk of an indigenous New Zealand passerine, Mohua ochrocephala.

Pest control is a key activity undertaken to conserve threatened and declining species. Although bioeconomic analysis has been used to contrast the relative efficiency of control strategies where pests affect economic resources, the same approaches have been adopted rarely in conservation settings. The Mohua (Mohoua ochrocephala) is an insectivorous passerine indigenous to beech (Nothofagus spp.) forests in New Zealand's south island. Mohua have undergone a 75% range contraction since stoats (Mustela erminea) (which prey on nests and nesting females) were introduced to the south island in the late 1800s. Mohua nests are particularly vulnerable when stoat abundance increases in response to eruptions in the density of introduced house mice (Mus musculus), which in turn respond to semiperiodic (4-6year) mass seeding (masting) of beech trees. Controlling stoats only when their abundance poses a threat to Mohua fledging success would theoretically maximize the efficiency with which Mohua are protected. To better synchronize stoat control with periods of high stoat density, control could be initiated according to (1) time since last control, (2) beech seedfall, (3) mouse abundance, or (4) stoat abundance. Monitoring the three environmental cues, however, incurs costs that should be taken into account when considering their relative efficiency I derived an empirically based stochastic model that links sequential change in beech seedfall, mouse, and stoat abundance to a simple demographic model for Mohua. I used the model to contrast the relative cost-efficiency of achieving conservation outcomes for Mohua (specified in a quasi-extinction framework), initiating stoat control according to these cues. The use of environmental cues reduced the frequency with which stoat control had to be undertaken to achieve Mohua conservation outcomes by more than 50%. For some cues, however the costs of monitoring outweighed the savings that could be achieved through reduced frequency of stoat control. The interplay between costs of monitoring environmental cues and the frequency with which stoat control had to be undertaken meant that the most efficient strategy was dependent on the conservation outcome specified for Mohua. My results demonstrate the utility of bioeconomic analysis in formulation of pest management strategies to achieve conservation outcomes.

Animals↗

PubMed1995

[Voluntary, controlled limited reproduction in humans--a conflict to modern evolutionary biology?].

In western industrialized countries it is widespread to limit individual reproduction voluntarily and deliberately. This phenomenon of minimizing reproduction conflicts with the maximization of biological fitness, expected on the basis of sociobiology. Some positions and attitudes of demography and sociobiology that appear to be contradictive are critically discussed, and with several examples it is expounded that we are dealing with misunderstanding rather than inconsistencies in many cases. The majority of misunderstandings can be put down to an inadequate differentiation between proximate and ultimate levels of causation. However, proximate interpretations of the problem of minimizing reproduction from a sociobiological perspective are frequently unsatisfactory. Therefore, the demographic model of "competing pleasures of life" (Konkurrenz der Genüsse) was connected with evolutionary biology. Combining demographic and biological aspects reveals that human striving for material and non-material values (pleasures of life), originally was highly adaptive and fitness-enhancing as behaviors to acquire resources and secure social status. Not until a society offered a variety of behavioral and consumer alternatives and simultaneously sophisticated methods of contraception these behavioral patterns dissociated from their function of survival and became independent.

Adult↗

PubMed1985

The dynamics of urban population.

The relative roles of natural increase and migration in determining the long-term dynamics of an urban population are considered. "Rogers' model is used to represent the simultaneous growth of a multiregional population. Exploiting the mathematical structure of the resulting system of difference equations, a perturbation theory for demographic models [is] outlined. This theory provides useful tools for analysing the sensitivity of stable population distribution and rate of growth to changes in the fundamental demographic parameters. With respect to the conventional approach to sensitivity analysis, it does not require the sometimes cumbersome calculation of matrix derivatives." A numerical example is given to demonstrate the method. (SUMMARY IN FRE AND ITA)

Demography↗

PubMed1997

Malaria and mortality: some epidemiological considerations.

Malaria can, a priori, kill on its own ('direct' malaria mortality) or in conjunction with some other cause(s) ('indirect' malaria mortality). There are three distinct approaches to the measurement of malaria mortality: (1) measurement of malaria-specific mortality (based on attributing each death to a single cause) or its surrogate, the admission rate for life-threatening malaria; (2) measurement of the reduction in all-cause mortality after removal (or near removal) of malaria; and (3) the estimation of the malaria mortality required to explain the observed frequency of the HbS gene. There is a strong indication that approaches (2) and (3) yield estimates of total (direct and indirect) malaria mortality which are at least twice as high as those obtained using approach (1), which probably measures mostly direct malaria mortality. There is currently a controversy about the long-term impact on mortality of reducing the intensity of malaria transmission from 'high' to 'intermediate', given the expected loss of immunity. Certain geographical comparisons (of the results of 'nature's experiment') indicate that, when the intensity of transmission is high, the incidence of life-threatening malaria falls. However, the seasonal variation in the intensity of transmission decreases with increases in the intensity; low seasonal variation is probably beneficial, allowing a smoother transition from passive to active immunity, but is unlikely to be reversed by preventive measures. It also seems likely that geographical comparisons produce estimates of predominantly direct mortality, which might not run in parallel with the indirect mortality. A tentative numerical exploration of the problem, using a simple demographic model, indicates that, if indirect malaria mortality is important and the other causes of death are concentrated in early life, the long-term impact on all-cause mortality of reducing exposure (although less than the short-term) will probably always be beneficial, even if there is some increase in direct malaria mortality.

Animals↗

PubMed2001

Teenage pregnancy: a reflective analysis.

Analysis of interview data from a television programme was undertaken in order to reflect upon a 16-year old girl's specific experience of pregnancy. Five major themes emerged from the thematic data content analysis 'role-modelling', 'demographics', 'punishment', 'locus of control' and 'self-validation'. Analysis of the theme of 'role-modelling' suggests that constructions of childhood and concepts of health may be positively influenced by social learning. A client centred model of health promotion may aid health care workers when trying to promote the health of these young girls given the appropriate resources.

Adolescent↗

PubMed1986

Population forecasts and confidence intervals for Sweden: a comparison of model-based and empirical approaches.

This paper compares several methods of generating confidence intervals for forecasts of population size. Two rest on a demographic model for age-structured populations with stochastic fluctuations in vital rates. Two rest on empirical analyses of past forecasts of population sizes of Sweden at five-year intervals from 1780 to 1980 inclusive. Confidence intervals produced by the different methods vary substantially. The relative sizes differ in the various historical periods. The narrowest intervals offer a lower bound on uncertainty about the future. Procedures for estimating a range of confidence intervals are tentatively recommended. A major lesson is that finitely many observations of the past and incomplete theoretical understanding of the present and future can justify at best a range of confidence intervals for population projections. Uncertainty attaches not only to the point forecasts of future population, but also to the estimates of those forecasts' uncertainty.

Forecasting↗

PubMed2006

Experimental support of the scaling rule for demographic stochasticity.

A scaling rule of ecological theory, accepted but lacking experimental confirmation, is that the magnitude of fluctuations in population densities due to demographic stochasticity scales inversely with the square root of population numbers. This supposition is based on analyses of models exhibiting exponential growth or stable equilibria. Using two quantitative measures, we extend the scaling rule to situations in which population densities fluctuate due to nonlinear deterministic dynamics. These measures are applied to populations of the flour beetle Tribolium castaneum that display chaotic dynamics in both 20-g and 60-g habitats. Populations cultured in the larger habitat exhibit a clarification of the deterministic dynamics, which follows the inverse square root rule. Lattice effects, a deterministic phenomenon caused by the discrete nature of individuals, can cause deviations from the scaling rule when population numbers are small. The scaling rule is robust to the probability distribution used to model demographic variation among individuals.

Animals↗

PubMed1997

An age-structured model for pertussis transmission.

The vaccination program for pertussis (whooping cough) in the United States consists of giving multiple doses of pertussis vaccine to young children. A demographic model with a steady-state age distribution is used as a basis for building an epidemiologic model for the transmission of pertussis. This age-structured model includes vaccination of infants and children for pertussis with waning of both infection-acquired and vaccine-induced immunity. Computer simulations of the mathematical model between 1940 and 2040 show the changes that took place during the implementation phase of the U.S. program and predict only minor future changes in the age distribution and incidence of pertussis if the vaccination program is maintained at the 1995 level. The sensitivities of these results to changes in demographic and epidemiologic parameters, vaccine efficacy, duration of protection, and levels of vaccination coverage are investigated.

Adolescent↗

PubMed2000

Sexually transmitted infections and risk behaviours in women who have sex with women.

OBJECTIVES: To assess the prevalence of sexually transmitted infections (STIs) and blood borne viruses, risk behaviours, and demographics in women who have sex with women (WSW). METHODS: Retrospective cross sectional study using a multivariate model. Demographic, behavioural, and morbidity data were analysed from standardised medical records of patients attending a public STI and HIV service in Sydney between March 1991 and December 1998. All women with any history of sex with a woman were compared with women who denied ever having sex with another woman (controls). RESULTS: 1408 WSW and 1423 controls were included in the study. Bacterial vaginosis (BV) was significantly more common among WSW (OR 1.7, p < 0.001). Abnormalities on cervical cytology were equally prevalent in both groups, except for the higher cytological BV detection rate in WSW (OR 5.3, p = 0.003). Genital herpes and genital warts were common in both groups, although warts were significantly less common in WSW (OR 0.7, p = 0.001). Prevalence of gonorrhoea and chlamydia were low and there were no differences between the groups. The prevalence of hepatitis C was significantly greater in WSW (OR 7.7, p < 0.001), consistent with the more frequent history of injecting drug use in this group (OR 8.0, p < 0.001). WSW were more likely to report previous sexual contact with a homo/bisexual man (OR 3.4, p < 0.001), or with an injecting drug user (OR 4.2, p < 0.001). Only 7% of the WSW reported never having had sexual contact with a male. CONCLUSION: We demonstrated a higher prevalence of BV, hepatitis C, and HIV risk behaviours in WSW compared with controls. A similar prevalence of cervical cytology abnormalities was found in both groups. Measures are required to improve our understanding of STI/HIV transmission dynamics in WSW, to facilitate better health service provision and targeted education initiatives.

Adolescent↗