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PubMed2002

Influence of patient, visit, and oral health factors on dental service provision.

OBJECTIVES: Service provision should reflect the oral health of the patient. However, patient and visit factors may influence service patterns and the appropriateness of care delivered. The aim of this study was to examine factors associated with variation in dental services and to assess whether variation by patient and visit characteristics persisted after controlling for oral health status. METHODS: A random sample of Australian dentists was surveyed during 1997-98 (response rate = 60.3%). Private general practitioners (n = 345) provided data on service provision, as well as patient, visit and oral health variables from a log of a typical clinical day (n = 4,115 patients). Multivariate Poisson regression models were run for eight service areas (e.g., diagnostic, preventive, and restorative). RESULTS: Significant effects (P < .05) were observed for oral health factors in all eight models, visit factors in all eight models, patient demographics in four models, dental knowledge/behavior in one model, and area-based socioeconomic status in one model. CONCLUSIONS: After controlling for oral health, visit characteristics persisted as significant predictors of services, with nonemergency visits, insurance, and capital city location associated with more favorable service mix patterns. Higher socioeconomic status areas and payment scale ratings also were associated with a better service pattern in particular service areas. These findings show that a wide range of factors, in addition to oral health, contribute to variation in service provision.

Adolescent↗
PubMed2004

Demographic analysis and modeling of human populations exposed to ionizing radiation.

The health effects of ionizing radiation on human populations are often analyzed using epidemiological statistical methods. Because of the complexity of the health consequences of ionizing radiation and the prolonged period during which the consequences emerge, we propose to evaluate these health effects using mathematical models that are based on the best theoretical reasoning and prior biological evidence about disease mechanisms. We believe this will improve the ability of the model to identify health effects and reduce erroneous inferences.

Demography↗
PubMed1989

U.S. births and limit cycle models.

Lee's (1974) formal demographic feedback models summarize the implications for births and age-structure of neo-Malthusian theories of baby booms such as those of Easterlin. For some parameter values, such models imply sustained cycles, so-called "limit cycles", in births. Frauenthal and Swick recently reestimated a continuous-age version of Lee's basic cohort model with U.S. series and, contrary to Lee's original findings, concluded that "limit cycles oscillations have been occurring in U.S. births." This article disputes their conclusion, ascribing it to an inconsistency in detrending procedures. Furthermore, it corrects Lee's original conclusion by showing that his alternative period labor-force feedback model, estimated from U.S. series, leads to cycles of implausibly long period. This article thus reopens the question of whether any feedback model could account for the observed cycles in U.S. births.

Adolescent↗
PubMed1996

An SEI model with density-dependent demographics and epidemiology.

Two compartmental models for the dynamics of an infectious disease in a wild-animal population are analysed. The models feature density-dependent birth, death, and contact rates, and pseudovertical disease transmission. For the SI model it is shown that up to four steady states may exist, depending on the parameter values, and that one of these states is globally stable. For the SEI model four equivalent steady states exist, but periodic solutions are now possible for some parameter values.

Animals↗
PubMed2000

What students bring to medical school: attitudes toward health promotion and prevention.

INTRODUCTION: Health care providers' positive attitudes toward prevention and health promotion are important in achieving national health care goals. Limited studies of incoming medical students have been conducted that measure predictors of positive attitudes toward health promotion and prevention. METHODS: Data were obtained from a 1993 curriculum evaluation survey of first-year students at five different medical schools in California. Attitudes toward health promotion and prevention were measured using a nine-question Prevention Attitude Scale (PAS). We developed 2 multivariate linear regression models using demographics, education choices, and personal social values and beliefs to predict PAS scores. We also performed bivariate analysis. RESULTS: Five hundred ninety-nine completed surveys were analyzed, with a response rate of 95%. Mean PAS score was 36.47 +/- 3.7 on a 0 to 44 scale. Female gender, Democratic party preference, and a planned specialty choice in preventive medicine or primary care predicted the highest PAS scores on bivariate analysis (p < 0.002). Significant correlation ( p < 0. 001) was shown between PAS scores and 2 additional scales regarding beliefs in associations of social factors and illness and in the importance of caring for the poor. Linear regression model using personal social values and beliefs explained 34% of the variance, as opposed to the demographic model that explained only 9% of the variance. CONCLUSIONS: In the schools studied, participating first-year medical students had moderately positive attitudes toward health promotion and prevention, as measured by PAS scores. In designing curriculum to improve medical students' attitudes toward health promotion and prevention, medical educators may need to consider other personal and social values held by medical students and to address the "political" aspects of health promotion and prevention. Future studies are needed to longitudinally follow medical student attitudes.

Adolescent↗
PubMed1985

Input-output models for regional demographic-economic analysis: some structural comparisons.

"In this paper is presented a comparative survey of the many ways in which a static Leontief input-output model can be extended to include demographic-economic relationships. A family of ten input-output models is identified, with individual members defined according to their representation of household income, employment, and unemployment. Miyazawa's fundamental equation of income formation is generalised and used to establish structural relationships between the models, as reflected in income and employment impact-multipliers. Although the emphasis of the paper is theoretical, examples are given of the empirical application of existing models."

Demography↗
PubMed1987

[Demographic consequences of genetic load: a model of the origin of the incest taboo].

The prohibition of copulations among near relatives may raise the fitness of population. This effect being irregular and insignificant for a distinct generation, becomes apparent in evolutionary time intervals through the natural selection of populations with incest-taboo. The "characteristic selection time" theta depends on typical population size, genetic damage and the mean rate of population growth. The estimation obtained for theta permit us to assert that the model describes the phenomenon of "socio-cultural selection" in prehistory. The model shows the demographic specificity of small populations. The problem of the number of consanguineous marriages is considered in detail. New explanation for deviation of the observed frequency of consanguineous marriages from classical estimations is proposed.

Genes, Lethal↗
PubMed1990

Chronic care: a future delivery model?

If demographic predictions are right, the chronic care patient population will have a significant effect on future health care delivery systems. As baby-boomers age and become debilitated with chronic disease and conditions, and as premature babies and young trauma and chronic disease victims survive with increased disability, acute care hospital administrators will have to focus more attention on these patients. But what is this patient population like? One of the steps to understanding the chronic care market is to form a realistic profile of these patients, say executives. They are not all elderly, and they are not all near death. But they are savvy consumers who demand high-quality, patient-centered care.

Bed Conversion↗
PubMed1997

What demographers can learn from fruit fly actuarial models and biology.

Historically demographers have viewed the results of actuarial studies of nonhuman species, particularly those on invertebrates such as fruit flies, as largely irrelevant to investigations on human populations. In this paper I present life table data from large scale studies on the Mediterranean fruit fly, and show that they provide important insights into fundamental aspects of mortality relevant to human populations: the trajectory of mortality at older ages, sex mortality differentials, the concept of maximal life span, and demographic heterogeneity and selection. An overriding theme of the paper is the need for demographers to acquire a heightened awareness of new developments in biology including areas such as evolutionary ecology, experimental demography, and molecular medicine.

Age Distribution↗
PubMed1997

Analysis of completed parity using microsimulation modeling.

"This paper aims to construct a demographic microsimulation model, which is easily applicable to gene transmission..., and to examine the distribution of completed parity as a fertility measure at a population level according to the schedule of individual life course....The simulation model was applied to the data of the Gidra-speaking people living in the lowlands of Papua New Guinea."

Birth Rate↗
PubMed2001

Modeling complex disease with demographic and environmental covariates and a candidate gene marker.

We randomly chose replicates 28 and 29 of the simulated data sets of Genetic Analysis Workshop 12 to model the dependence of affection status on covariates, quantitative traits, and genes using all living pedigree members. First we explored the relationship of affection status to demographic and environmental factors using logistic regression and the Cox proportional hazards models. In the second stage of our analyses the generalized transmission disequilibrium test (GTDT) was applied to nuclear families with at least two affected siblings to select single markers and high-risk alleles, which were tested in the population association analyses including all pedigree members. Multiple logistic regression models were fitted to investigate the joint contributions of genetic and nongenetic factors and a block-recursive modeling approach was adopted to study inherent hierarchical dependence structure in the data. We found that allele 2 on marker 35 of chromosome 6 is associated with higher risk compared with the other 3 alleles of this marker. In addition to this significant genetic effect, age at exam and four of the five quantitative traits (QT1, QT2, QT4, and QT5) had a significant association with the disease. Our results were obtained without knowledge of the true disease generating models.

Adolescent↗
PubMed1994

Parameterizing age patterns of demographic rates with the multiexponential model schedule.

"For nearly 200 years actuaries, statisticians, and demographers have sought to summarize the age pattern of mortality rates by means of a limited number of parameters. Such 'model schedules' have also been useful in representing schedules of rates other than mortality....This paper illustrates a particular general functional form for such model schedules: the multiexponential function. It discusses the changing behavior of this function as its parameters take on different values and examines the quality of the fits of this function to observed data on mortality, fertility, and migration." This is a revised version of a paper originally presented at the 1993 Annual Meeting of the Population Association of America. (SUMMARY IN FRE)

Demography↗
PubMed1983

Potential savings from the adoption of nurse practitioner technology in the Canadian health care system.

An investigation is reported of the potential for reducing aggregate medical costs by the introduction of nurse practitioners into the Canadian health care system to an extent consistent with demonstrated safety and effectiveness. A cost model is developed for this purpose and estimates of its parameters are provided. The cost model is coupled with a demographic projection model and potential cost reductions are simulated over the period 1980-2050, under alternative assumptions. Results suggest that savings could have been in the range 10-15% in 1980 for medical services as a whole, and 16-24% for ambulatory services. The estimated savings percentages are quite insensitive to projected changes in the age structure of the Canadian population.

Canada↗
PubMed1990

Endemic disease in host populations with fully specified demography.

This study explores the epidemiology of an aerogenically transmitted infectious disease following an S.I.R. pattern in a host population with completely specified age-specified maternity and mortality schedules. A fully age-structured demographic-epidemiologic model is developed, and its demographic and epidemiologic behaviour is explored in numerical studies. The impact of variations in host population demographic structure upon the effect of immunization programs is also studied.

Age Factors↗
PubMed2003

Modeling momentum in gradual demographic transitions.

The analysis of population momentum following a gradual decline in fertility to replacement level provides valuable insights into prospects for future population growth. Here, we extend recent work in the area by applying a new form of the quadratic hyperstable (QH) model, which relates exponentially changing fertility to the resultant exponentiated quadratic birth sequence. Modeling gradual transitions from an initial stable population to an ultimate stationary population indicates that such declines in fertility increase momentum by a product of two factors. The first factor is a previously noted continuation of stable growth for half the period of decline. The second is a not previously appreciated offsetting factor that reflects the interaction between the decline in fertility, the changing age pattern of fertility, and the changing age composition of the population. Numerical examples using both hypothetical and actual populations demonstrate that for declines of any length, the product of the two factors yields momentum values that closely agree with the results of population projections. The QH model can examine monotonic transitions between any two sets of constant vital rates. As a generalization of the fixed-rate stable model, it has great potential value in numerous areas of demographic analysis.

Birth Rate↗
PubMed2004

Complexity and demographic stability in population models.

This article is concerned with relating the stability of a population, as defined by the rate of decay of fluctuations induced by demographic stochasticity, with its heterogeneity in age-specific birth and death rates. We invoke the theory of large deviations to establish a fluctuation theorem: The demographic stability of a population is positively correlated with evolutionary entropy, a measure of the variability in the age of reproducing individuals in the population. This theorem is exploited to predict certain correlations between ecological constraints and evolutionary trends in demographic stability, namely, (i) bounded growth constraints--a uni-directional increase in stability, (ii) unbounded growth constraints (large population size)--a uni-directional decrease in stability, (iii) unbounded growth constraints (small population size)--random, non-directional change in stability. These principles relating ecological constraints with trends in demographic stability are shown to be far reaching generalizations of the tenets derived from classical studies of stability in an evolutionary context. These results thus provide a new conceptual framework for explaining patterns of variation in population numbers observed in natural populations.

Age Factors↗