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PubMed2003

Conservation and control strategies for the wolf (Canis lupus) in western Europe based on demographic models.

Securing the long-term acceptance of large carnivores such as the wolf (Canis lupus) in Europe and North America raises a difficult challenge to conservation biologists: planning removals to reduce depredations on livestock while ensuring population viability. We use stochastic-stage-structured population models to investigate wolf population dynamics and to assess alternative management strategies. Among the various management strategies advocated by agencies, zoning that involves eliminating wolves outside a restricted area should be designed with caution, because probabilities of extinction are extremely sensitive to the maximum number of packs that a zone can support and to slight changes in stage specific survival probabilities. In a zoned population, viability is enhanced more by decreasing mortality rates in all classes than by increasing wolf zone size. An alternative to zoning is adaptive management, where there is no limit on pack number but population control can be operated whenever some predefined demographic conditions are met. It turns out that an adaptive management strategy that removes a moderate percentage (10%) of the population following each year of more than 5% of total population growth would provide visible actions addressing public concerns while keeping extinction probability low.

Animals↗
PubMedDate not supplied

Modern African ape populations as genetic and demographic models of the last common ancestor of humans, chimpanzees, and gorillas.

In order to fully understand human evolutionary history through the use of molecular data, it is essential to include our closest relatives as a comparison. We provide here estimates of nucleotide diversity and effective population size of modern African ape species using data from several independent noncoding nuclear loci, and use these estimates to make predictions about the nature of the ancestral population that eventually gave rise to the living species of African apes, including humans. Chimpanzees, bonobos, and gorillas possess two to three times more nucleotide diversity than modern humans. We hypothesize that the last common ancestor (LCA) of these species had an effective population size more similar to modern apes than modern humans. In addition, estimated dates for the divergence of the Homo, Pan, and Gorilla lineages suggest that the LCA may have had stronger geographic structuring to its mtDNA than its nuclear DNA, perhaps indicative of strong female philopatry or a dispersal system analogous to gorillas, where females disperse only short distances from their natal group. Synthesizing different classes of data, and the inferences drawn from them, allows us to predict some of the genetic and demographic properties of the LCA of humans, chimpanzees, and gorillas.

Africa↗
PubMed1983

A demographic model for performing site-specific health risk projections.

An extension of an earlier life table model for estimating health risks in occupationally exposed workers is presented. The extension of the earlier methodology incorporates specific fertility assumptions and therefore produces a model that is able to perform health risk projections for populations living in or around sites that release agents with potentially adverse health consequences. Results show that fertility patterns are important for assessing risk, even for short-term projections. The interaction of initial age structure, competing risks from other causes of death, and fertility patterns are all important in determining future levels of excess mortality from various pollutants.

Actuarial Analysis↗
PubMed1994

Implications of hormonal influences on sexual behavior for demographic models of reproduction.

In exploring the implications of hormonal influences on sexual behavior for reproduction, we have focused on androgens because of the convincing evidence for androgenic effects on female sexual motivation. We have been guided by the simple idea, based on clinical findings among hyperandrogenic women, that higher testosterone levels will increase female sexual motivation which in turn will result in increased coital frequency. However, careful consideration of the evidence fails to confirm such a role for testosterone in sexual behavior among normal women at any point in the reproductive span. While some amount of testosterone appears to be important in maintaining female sexual motivation, there is little evidence that variation in testosterone within the normal range is associated with variation in sexual motivation. Reported associations between testosterone and sexual behavior among married women cannot be interpreted as resulting from androgenic effects on sexual motivation. Thus we are left with the task of explaining why testosterone does not appear to play the same role in libido among hyperandrogenic and normal women. As mentioned earlier, some of the difference may attributable to the much higher levels of testosterone among hyperandrogenic women. Sherwin points out that the levels of sexual motivation decline with declining testosterone levels even while testosterone is well above normally occurring levels. It is possible that the brain is simply not sensitive to the variation in testosterone levels found in normal women. Other evidence suggests that the presence of intact ovaries may be equally important. A recent study of androgen replacement in naturally post-menopausal women failed to find a dramatic effect of testosterone on sexual motivation and behavior, despite levels similar to those in studies on surgically menopausal women, pointing to the importance of other factors associated with the presence of ovaries. A similar point can be made with regard to hyperandrogenism related to endogenous sources of testosterone, as in the case of PCOS. High levels of testosterone effectively disrupt ovarian function and interfere with other ovarian processes. Among hyperandrogenic women sexual behavior appears to be related to the direct effects of androgens on motivation, while the indirect effects of estrogen and progesterone are essentially eliminated. Among normal women, on the other hand, there is little evidence for such a dominating role of a direct androgenic effect on sexual behavior. Instead, other ovarian hormones, including estrogen and progesterone may also play a demonstrable role, despite the lack of strong evidence at this point.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1994

[Medico-demographic models in psychiatry].

The paper presents data on current mental disease prevalence, on some aspects of psychiatric service management, on social damage inflicted by psychic diseases and financial resources the society is willing to give off for relevant compensations. The importance of social modelling of the patients for prognostication of their life and estimation of the disease-induced damages is emphasized. Different forms of therapeutic modalities in psychiatry are analyzed in terms of efficacy. The authors draw attention of health service officials to poor reserves and outdated management of psychiatric service in the country.

Demography↗
PubMed1993

[A demographic model of hospitalization rates in the population of the Czech Republic as a tool for evaluation of inter-district differences].

The authors elaborated a computer model of the hospitalization rate of the population, using the method of indirect standardization which can apply the available specific hospitalization rate of a major territorial unit by age and sex to defined regional sub-populations. The model was used to the calculation of the theoretical standardized hospitalization rate in hospitals and sanatoria for chronic patients in Prague and different district of the Czech Republic, using the specific hospitalization rate of the whole Czech Republic as a standard for 1986 to be compared with the actual number of patients hospitalized in that year. The ratio of the actual number of hospitalized patients and the calculated standard for 1986 varied between 73.5% in the district Plzen-north and 125.9% in the Bruntal district. In the Bruntal district the age standardized hospitalization rate was thus by more than 70% higher than in the Plzen-north. In district with the highest ratio of the actual and standardized number of hospitalized patients there was in all instances a relatively great excess of beds which was obviously the main subjective reason for the high hospitalization rate of the population. In the district of Cheb, Svitavy, Most, Chomutov and Bruntal there were, as compared with the Czech average of 400 almost some 600 beds in hospitals and sanatoria for chronic patients in excess. The hospitalization rate of the population in the Czech Republic in 1986 is compared with that in Holland in 1989-1991 and it was found that the comparable Czech data were by 1.8 times higher.

Adolescent↗
PubMed1983

The design and implementation of a regional economic-demographic simulation model.

The management of urban growth patterns in the United States in order to maximize the benefits of public and private investments in urban areas is examined. The authors present "the results of a modelling design effort to link a hybrid regional input-output model to demographic, labor force and energy models for use in planning in the San Francisco Bay Region. Extensive use of system feedback is a major component of this research effort. Summary results of the model outputs are presented...."

Americas↗
PubMed1996

Capitation adjustment for pediatric populations.

OBJECTIVE: The objective of this study is to assess the predictive performance of current claims-based capitation adjustment methods for pediatric populations. Medicaid programs and other insurers may increasingly use these systems for capitation rate setting, physician profiling, and other purposes. METHODS: Five leading models, a demographic model, ambulatory care groups, ambulatory diagnostic groups, diagnostic cost groups, and payment amounts for capitated systems, were tested by using use and expenditure data for children enrolled in the Maryland Medicaid program and a private nonprofit health maintenance organization in Minnesota. The models were tested at the individual level by using multiple regression methods and at the group level by using split-half validation to create both random and nonrandom groups. One of the nonrandom groups was created to represent children with chronic conditions. RESULTS: The findings indicate that although each of the alternative methods offers an improvement over a demographic model, significant underpayment remained for high-risk children, regardless of the capitation adjustment method used. CONCLUSIONS: It is concluded that children with chronic conditions would probably remain at risk for discrimination in a competitive health care market under all models tested. Limitations associated with current alternatives suggest the need for further research in the area of pediatric capitation adjustment methods.

Adolescent↗
PubMed1999

Development and estimation of a pediatric chronic disease score using automated pharmacy data.

BACKGROUND: Although risk assessment models for specific adult populations such as the elderly have been developed, little work has focused on developing pediatric-specific models. The lack of pediatric models may result in incorrect estimates of relative disease severity among children, in reduced reimbursement for health plans and providers, and in inadequate health care for chronically ill children. OBJECTIVES: To develop and to evaluate a pediatric risk assessment model using automated pharmacy data. DESIGN: Retrospective, case-cohort study using automated data. SUBJECTS: All children continuously enrolled in Group Health Cooperative of Puget Sound during 1992 and 1993. MEASURES: The Pediatric Chronic Disease Score (PCDS), an algorithm that classified children into chronic disease categories by prescription drug fills, was compared with the ICD-9-CM-based Ambulatory Care Groups (ACG) model and a demographic model for prediction of total, ambulatory, or primary care costs and primary care visits. Forecast models were estimated using linear regression and they were evaluated with R2, mean prediction error, mean squared prediction error, and Mincer-Zarnowitz tests. RESULTS: The pharmacy-based PCDS performed significantly better on each of the four forecasting accuracy tests than did a demographic model (eg, R2s averaging fourfold higher). Compared with the ACG model, the PCDS model performed similarly on mean squared prediction error tests; however, the ACG generally had higher validation R2 values. CONCLUSIONS: A pharmacy-based pediatric risk assessment model performs better than a demographic model and represents a viable alternative to ICD-9-CM-based models. Further research is necessary to determine if children must be considered separately from adults when conducting population-based risk assessments.

Adolescent↗
PubMed2002

Demographic development of the middle Dalmatian coast and simulation of trends in population density by the LOPI model.

Demographic development of middle Dalmatian settlements: Jesenice, Mimice, Zivogosće and Zaostrog was followed during the period between 1857 and 1991. On the basis of the analysis, we can conclude that the positive trends in the number of residents were interrupted during the first decades of the 20th century, while the stagnation and decrease of the total number of residents prevailed during the following period. In other words, depopulation was established as a stable demographic process. Population's gender structure was uniform during the rolls in 1971, 1981 and 1991 in all four settlements. During the same period, the age structure of the population showed that the older residents prevailed over younger residents (prereproductive and repoductive population) in all four settlements (Jesenice, Mimice, Zivogosće and Zaostrog). Furthermore, all settlements belonged to the regressive or stationary types of age structure (neither belonging to the progressive type). We have used the LOPI model for the mathematical modeling of demographic processes of the middle Dalmatian population. On the basis of the LOPI model the results show very good accordance between the simulated data and actual values in the settlements of Zivogosće and Zaostrog. The settlements of Jesenice and Mimice showed also very good accordance between the simulated data and actual values, but only until 1920 (Jesenice) and 1910 (Mimice) year.

Adolescent↗
PubMed1984

An assessment of the accuracy of a regional economic-demographic projection model.

A large number of regional economic-demographic projection models have been developed but their accuracy has seldom been evaluated. This article examines the accuracy of one such model in projecting total populations for 1980, using 1970 base data, for 106 counties and 553 places in two states. Comparisons of the model's projections to 1980 Census counts reveal mean percentage absolute differences of 10 percent for counties and 14 percent for places. In addition, the model's accuracy was comparable to that for alternative projection systems. When projections for places of less than 1,000 are excluded, differences are substantially reduced. Economic-demographic models appear to be quite useful and deserve further attention.

Demography↗