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PubMed1998

Cognitive and Metacognitive Abilities Involved in the Solution of Mathematical Word Problems: Validation of a Comprehensive Model.

With this investigation we tried to validate an economic model of the cognitive and metacognitive abilities involved in Mathematical Word Problems. From the literature we chose seven abilities: text comprehension, problem representation, problem categorization, solution estimate, planning the solution, procedure self-evaluation, calculus self-evaluation. In order to measure these abilities, we devised a series of mathematical word problems (partitioned problem) where, for each ability, subjects have to answer a multiple choice question. A hierarchical regression model with only five variables (excluding solution estimate and calculus self-evaluation) explained more than 50% of the variance of the solution scores of the Partitioned Problems, and 40% of the variance of the solution of a series of problems presented with only the text. The model was validated with five different samples of subjects of different school grade and with a bootstrap procedure. Furthermore the relationship of the variables was tested using a path analysis. The discrimination validity of three different levels of problem solving efficiency give further support to the validity of the model. The model obtained may be utilized in order to devise practical instruments for the analysis of mathematical word problem difficulties. Copyright 1998 Academic Press.

Journal Article↗
PubMed2007

Using economic analysis to evaluate the potential of multimodality therapy for elderly patients with locally advanced pancreatic cancer.

PURPOSE: Development of new and expensive drugs with activity against pancreatic cancer has made economic considerations more relevant to treatment decision-making for advanced disease. Economic modeling can be used to explore the potential of such novel therapies and to inform clinical trial design. METHODS AND MATERIALS: We developed a Markov model to evaluate the cost-effectiveness of radiation plus fluorouracil (RT-FU) relative to no treatment in elderly patients with locally advanced pancreatic cancer (LAPC) and to determine the economic potential of radiation plus gemcitabine (RT-GEM), a novel regimen for this disease. We used the SEER-Medicare database to estimate effectiveness and costs supplemented by data from the literature where necessary. RESULTS: Relative to no treatment, RT-FU was associated with a cost-effectiveness ratio (ICER) of $68,724/QALY in the base case analysis. Compared with RT-FU, the ICER for RT-GEM was below $100,000/QALY when the risk of dying with the new regimen was <85% than with the standard regimen. However, >1,000 subjects would be necessary to demonstrate this level of efficacy in a randomized trial. The ICER of RT-GEM was most sensitive to utility values, and, at lower efficacy levels, to costs of gemcitabine and treatment-related toxicity. CONCLUSIONS: In elderly patients with LAPC, RT-FU is a cost-effective alternative to no treatment. The novel regimen of RT-GEM is likely to be cost-effective at any clinically meaningful benefit, but quality-of-life issues, drug acquisition, and toxicity-related costs may be relevant, especially at lower efficacy levels.

Aged↗
PubMed1998

Infectious disease transmission and infection-dependent matching.

This paper uses commonly available prevalence estimates to bound future incidence. The bounds rely on restricting the fraction of contacts between individuals of different infection statuses. It is argued that these bounds can be further tightened by restrictions of economic models of infectious disease that imply that uninfected individuals have larger incentives to avoid matching with infected individuals than do the infected individuals themselves. This implies that incidence predictions from canonical models of infectious disease are worst-case upper bounds, with the degree to which they overestimate new cases being monotonically related to this type of infection-dependent matching. Evidence in support of the economic type of infection-dependent matching is presented, by using data on the joint distribution of partners' HIV statuses in a random sample of couples from San Francisco in 1988-1989.

Communicable Diseases↗
PubMed2001

Measuring Alzheimer's disease progression with transition probabilities: estimates from CERAD.

OBJECTIVES: To estimate annual transition probabilities (i.e., the likelihood that a patient will move from one disease stage to another in a given time period) for AD progression. Transition probabilities are estimated by disease stages (mild, moderate, severe) and settings of care (community, nursing home), accounting for differences in age, gender, and behavioral symptoms as well as the length of time a patient has been in a disease stage. METHODS: Using data from the Consortium to Establish a Registry for Alzheimer's Disease (CERAD), the authors employed a modified survival analysis to estimate stage-to-stage and stage-to-nursing home transition probabilities. To account for individual variability, a Cox proportional hazards model was fit to the CERAD data to estimate hazard ratios for gender, age (50 to 64, 65 to 74, and more than 75 years), and level of behavioral symptoms (low/high, according to responses to the Behavioral Rating Scale for Dementia) for each of the key stage-to-stage and stage-to-nursing home transitions. RESULTS: The transition probabilities underscore the rapid progression of patients into more severe disease stages and into nursing homes and the differences among population subgroups. In general, male gender, age under 65, and high level of behavioral symptoms were associated with higher transition probabilities to more severe disease stages. Disease progression is roughly constant as a function of the time a patient has spent in a particular stage. CONCLUSIONS: Transition probabilities provide a useful means of characterizing AD progression. Economic models of interventions for AD should consider the varied course of progression for different population subgroups, particularly those defined by high levels of behavioral symptoms.

Aged↗
PubMed1998

A deterministic model for the economic evaluation of broiler production systems.

A deterministic model for the economic evaluation of broiler production and the derivation of economic values in broiler breeding was developed and tested. The model distinguishes four production stages: multiplier breeder, hatchery, commercial grower, and processor. The processor is included to determine relationships for the price per kilogram of live weight and the quality of the carcass, either on a "whole sale" or "further processed" base. Quantity of product output for the system is fixed by a predetermined amount of kilogram carcass of final product broilers finished by the commercial grower. Profitability of production and cost prices per unit product for subsequent stages can be calculated. Exogenous parameters are easily changeable in order to calculate profitability and cost prices for different production levels or production circumstances. Economic values can be derived considering influences of changes in genetic merit for performance traits on profitability or cost price, for integrated and nonintegrated production systems. By changing exogenous parameters, the model can also be used to analyze profitability or derive economic values for other meat-type poultry, such as turkey.

Agriculture↗
PubMed2005

Scenarios on costs and savings of influenza treatment and prevention for Dutch healthy working adults.

OBJECTIVE: To assess the economic implications of strategies for influenza control among healthy working adults in The Netherlands. METHODS: The economic evaluation was based on a pharmaco-economic model from the societal perspective. This model involves the direct and indirect costs of vaccination or treatment and the direct and indirect savings (averted costs) due to the control strategy. Control strategies comprised treatment with oseltamivir and prevention with the influenza vaccine. Clinical and economic parameter estimates were derived from published literature, databases and expert opinions. Several scenarios for age-groups and employment contracts (full-time versus not) were elaborated in combination with Monte Carlo simulation for probabilistic sensitivity analysis. RESULTS: Consistently, net cost savings are estimated over the range of age groups and scenarios considered. Net savings are smallest for half-time workers. Incremental analysis indicates that on average prevention renders higher cost savings than treatment. CONCLUSION: We found a consistent picture of net cost savings for prevention through vaccination and treatment with oseltamivir of influenza in healthy working adults in The Netherlands.

Absenteeism↗
PubMed2001

Implications of a utility model for ultraviolet exposure behavior.

Over the past several decades, the incidence of skin cancer has reached epidemic proportions. Despite numerous efforts to increase public awareness of the risks associated with solar radiation, people continue to sunbathe, use indoor tanning facilities, avoid photoprotective clothing, and fail to use sunscreen. We propose using an economic model, the utility model, to better understand how to reduce tanning behaviors. This model has been widely applied in financial decision-making as well as in analysis of risk-taking behaviors such as smoking. The model takes into account both the current perceived benefits of tanning and the future long-term risks. People tend to discount the future; they tend to weigh current benefits more heavily than future risks. As predicted by the model, past prevention efforts that have focused on long-term benefits gained by sun-protective behavior have been largely ineffective. In the current social environment, we cannot expect tanning reduction measures based solely on health education to be very effective. Only by changing public perceptions of a tan will efforts to decrease ultraviolet exposure behavior likely be successful.

Decision Making↗
PubMed2006

Impact of antibiotic restrictions: the pharmaceutical perspective.

The development of new antibiotics is dependent on their performance in economic models that favour products with large markets, high levels of potential sales and low development risks. There is a trend toward more severe and more widespread market restrictions for the use of antibiotics, ostensibly to control resistance, though they may be enacted through the control of drug budgets. The restrictions reduce the potential earnings of new antibiotics. In addition, more stringent regulatory procedures increase development costs and risk. As a consequence, compared with drugs for other diseases, particularly chronic diseases, antibiotics perform poorly in economic decision models and are therefore less likely to be selected by pharmaceutical companies for continued development. Overall, this creates a conflict between the twin objectives of controlling resistance through antibiotic restriction and addressing resistance clinically through the introduction of new agents. Ultimately, this may lead to the accelerated loss of efficacy for currently available agents, as we become more dependent on them. Moreover, the new agents that we need to maintain our current levels of health will be lacking in pharmaceutical pipelines. Antibiotic resistance is inevitable; the development of new antibiotics is, however, under threat. Unless the market conditions can be economically rebalanced to encourage innovation and investment, or new models of pharmaceutical development can be applied to this area, the number of companies with active antibiotic research programmes will continue to fall. Just as we should not be complacent regarding the development of resistance, we should not be complacent in assuming that the antibiotics of tomorrow will be there when we need them.

Anti-Bacterial Agents↗
PubMed2004

A proactive approach can make site remediation less expensive.

Without any incentive to clean up a contaminated site, remediation is often delayed until the site owner is compelled to act by regulatory agencies. In such a context, the selected technology is typically the one that will reach the remediation goals as quickly as possible. Unfortunately, this criterion is often met by overly expensive technologies, resulting in high and sometimes unaffordable total remediation costs, leading to a remediation with a negative net benefit. This study examines the effects of time constraint and benefit value on the optimal remediation strategy for a diesel-contaminated site. This strategy is developed using the technico-economic model METEORS, which takes into account the technology's effectiveness, the uncertainty of the level of contamination, and the possibility of reducing this uncertainty through either an additional characterization (before selecting and applying a technology) or the monitoring of the remediation technology (during its use). Results of simulations with both economic and temporal constraints support a proactive approach to site remediation.

Biodegradation, Environmental↗
PubMed2003

New technologies and potential cost savings related to morbidity and mortality reduction in Class III/IV heart failure patients in Canada.

BACKGROUND: Heart failure affects 1-2% of the Canadian population. The 1-year mortality rates in New York Heart Association Class III/IV heart failure patients range from 11 to 44%. This study evaluates costs associated with current management of Class III/IV heart failure and potential savings if morbidity and mortality are reduced. OBJECTIVES: To construct an economic model to evaluate the components of treating Class III/IV heart failure patients in Canada and the resulting direct medical costs. The model also estimates the potential savings that could result from the introduction of a new technology such as cardiac resynchronization therapy that reduces morbidity and mortality. METHODS: The model evaluates costs of pharmacological therapy, medical care, laboratory and diagnostic tests, and complications, most commonly hospitalization. Estimates are based on a literature review, expert opinion, and standard cost sources using widely accepted health economic methods. RESULTS: The model, under conservative assumptions, estimates that Class III/IV heart failure costs between CAD$1.4 billion and CAD$2.3 billion in Canada overall. Costs are substantial on the provincial level as well and are estimated to be approximately CAD$700 million, CAD$500 million, and CAD$300 million in Ontario, Québec, and British Columbia, respectively. New treatments could bring substantial savings depending on their effectiveness-measured as reduction in morbidity and mortality-and the number of patients who receive that treatment. Potential savings in Canada could reduce the total annual costs for this group of patients by approximately 10% or up to CAD$200 million annually. CONCLUSIONS: The high level of morbidity and mortality in Class III/IV heart failure patients and costs associated with their care are an impetus for the development of new therapies such as cardiac resynchronization therapy, that could deliver long-term benefits including increased exercise tolerance, reduced hospitalizations, and improved quality of life. Successful therapies could provide substantial savings and present a favorable economic profile in the treatment of heart failure. In order to ensure that appropriate technologies are commercialized and marketed, prospective evaluation of new therapies should include critical assessment of direct medical costs in addition to evaluating morbidity, quality of life and survival.

Biomedical Technology↗
PubMed2005

Pharmacoeconomics of long-acting risperidone: results and validity of cost-effectiveness models.

Relapse is the primary cost driver in schizophrenia and is closely related to levels of adherence (compliance) with therapy. Both atypical antipsychotic agents and depot preparations have been shown to be useful in improving therapeutic adherence compared with oral conventional antipsychotic agents. Long-acting risperidone is a new formulation of an atypical antipsychotic agent that combines the pharmacological advantages of the atypical drugs with those of its mode of administration. The likelihood of improved compliance compared with existing treatment regimens implies that the higher acquisition costs would be offset by reduced rates of relapse. Economic models, which represent the health and economic outcomes of patients or populations under a variety of scenarios, are used to evaluate the economic implications of schizophrenia treatment. These models need to reflect clinical reality while simultaneously remaining as simple as possible. The assumptions and results need to be made transparent; data quality must be described explicitly; areas of uncertainty must be comprehensively explored through sensitivity analysis; and individual models must be validated, for example by comparing them with others in the therapeutic area. In this article, cost-effectiveness models of long-acting risperidone developed for different countries are discussed in terms of design, data sources and robustness, and the implications of the results for the treatment of schizophrenia are also reviewed. A discrete event simulation (DES) model that was developed using UK cost and treatment assumptions, in order to provide a 'proof of concept', is described. Country-specific models forthe United States, Canada, Germany, the Netherlands, France, Belgium, Italy and Portugal, using either DES or decision analytical structures, are then discussed. Comprehensive sensitivity analyses were conducted to assess the robustness of the results. In each case, long-acting risperidone produced additional clinical benefit and cost savings compared with other treatment strategies, despite significant variations in cost effectiveness and therapeutic approaches. In particular, improved adherence arising through the use of long-acting risperidone provides a cost-effective strategy for treating patients with schizophrenia, irrespective of the country analysed. The information generated in this analysis therefore provides one potential method for improving resource allocation and reducing the health burden related to schizophrenia.

Antipsychotic Agents↗
PubMed1995

Economics of hypertension control. World Hypertension League.

This paper summarizes the key aspects of the problem of estimating the economic burden of hypertension and hypertension-related disease, the use of economic models, and the opportunities for containing the costs. More information is needed on the population-attributable risk of hypertension in various countries, which is indispensable to estimate the part of hypertension in the burden of stroke and heart disease. The population and high-risk approaches to hypertension control also have economic consequences, which may vary in different societies and must be assessed to ensure proper allocation of resources. Cost-containment can be achieved by more selective diagnostic investigations and by opting for cheaper drugs, though the choice of treatment is difficult owing to uncertainties in the quality-of-life estimates.

Cerebrovascular Disorders↗
PubMed1997

Can markets give us the health system we want?

The purpose of this article is to reconsider the foundations of health economics as applied to the study of competition. It shows that conclusions concerning the purported desirability of competitive markets are based on a number of assumptions--many of which have heretofore been ignored--that typically are not fulfilled in the health care area. Once this is recognized market mechanisms no longer necessarily provide the best way to improve social welfare. The article is divided into two parts: competition and demand. Each of these sections presents and then critiques key assumptions of the conventional economic model, and then provides a number of health applications. It concludes that by not considering the validity of these assumptions in health care applications, researchers and policy analysts will bind themselves to policy options that may be most effective in improving social welfare.

Community Participation↗
PubMed2006

When are no-take zones an economically optimal fishery management strategy?

Discussions on the use of marine reserves (no-take zones) and, more generally, spatial management of fisheries are, for the most part, devoid of analyses that consider the ecological and economic effects simultaneously. To fill this gap, we develop a two-patch ecological-economic model to investigate the effects of spatial management on fishery profits. Because the fishery effects of spatial management depend critically on the nature of the ecological connectivity, our model includes both juvenile and adult movement, with density dependence in settlement differentiating the two types of dispersal. Rather than imposing a reserve on our system and measuring its effect on profits, we ask: "When does setting catch levels to maximize system-wide profits imply that a reserve should be created?" Closing areas to fishing is an economically optimal solution when the value derived from spillover from the reserve outweighs the value of fishing in the patch. The condition, while simple to state in summary form, is complex to interpret because it depends on the settlement success of the dispersing organisms, the nature of the costs of the fishing, the economic and ecological heterogeneity of the system, the discount rate, and growth characteristics of the fish population. The condition is more likely to be satisfied when the closed area is a net exporter of biomass and has higher costs of fishing, and for fish populations with density-independent settlement ("adult movement") than with density-dependent settlement ("larval dispersal"). Rather surprisingly, there are circumstances whereby closing low biological productivity areas, and even sometimes low cost areas to fish, can result in greater fishing profits than when both areas are open to fishing.

Animals↗
PubMed2001

INSIGHT: a framework for determining impacts of changes in land and water policies.

CSIRO Sustainable Ecosystems is constructing a spatially explicit modelling system capable of exploring alternative land and water policy alternatives against plausible price, cost, and climate scenarios for the next 20 years. INSIGHT will be used to identify the likely impacts of land and water policy options on regional economies and structural adjustment. Flowcharts have been constructed for most of the major crop and pasture and associated economic models for commodities produced in the Lachlan River Catchment of New South Wales. This enabled the most important components and interrelationships within these models to be readily identified. The next step has been to construct models at the regional scale that contain the essential elements of the more-detailed point models. The paper describes the progress to date in describing these models, and how they have been integrated into a coordinated agricultural crop production evaluation system.

Agriculture↗
PubMedDate not supplied

[Health-economic considerations for the use of BMP-2 for spinal surgery in Germany].

INTRODUCTION: BMP-2 can replace autogenous bone grafting in lumbar one-level anterior lumbar interbody fusions (ALIF). The current G-DRG system does not reimburse the upfront price of 2,970 euro per BMP-2 application for hospitals in Germany. The purpose of the current study was to create a health economic model to evaluate the financial savings for health care providers (hospitals) and health care payers (health care insurance) that can be achieved by the use of BMP-2 in spine surgery. METHODS: A previously published pooled data analysis was used in which BMP-2 showed significant improvements in the treatment after ALIF surgery compared to autogenous bone grafting, including earlier return to work time and reduced revision rates. These medical findings were transformed into economic data based on the regulations of the German health system of 2005. RESULTS: The significantly shorter return to work time under BMP-2 treatment generates important financial savings for health care insurances offsetting the upfront prize of 2,970 euro for BMP-2. Savings for hospitals are mainly related to shorter surgery time due to the absence of the bone grafting procedure and faster discharge of the patient. CONCLUSIONS: The combination of improved medical outcome by BMP-2 treatment for the patient and net savings for the entire health care system in Germany represents a "dominant" strategy from a health economic perspective. This implicates that BMP-2 in ALIF procedures is to be recommended from a health economic point of view for the German health care system.

Bone Morphogenetic Protein 2↗
PubMed2005

Path-dependent economic evolution with capital accumulation and education.

This paper proposes a dynamic economic model with wealth accumulation and human capital accumulation. The economic system consists of one production sector and one university. The university carries out education. The model describes a dynamic interdependence between wealth accumulation, human capital accumulation, and division of labor under perfect economic competition and the government intervention in education. We provide conditions for the existence of equilibrium points and stability of the nonlinear dynamic system. The simulation results demonstrate path-dependent processes of the nonlinear evolution. Some insights into East Asia's industrializing processes are provided.

Journal Article↗
PubMed1981

On the optimal choice of capital intensity in LDCs with migration.

"Sen's classic work on the choice of capital intensity of investment is generalized in the light of new theoretical developments and empirical findings concerning rural-to-urban migration in LDCs. This is done by explicitly incorporating a migration function into the basic choice model. Revised conditions for maximization of surplus are derived and compared with Sen's original condition. Some justification for the particular migration function used in the presence of risk-aversion is suggested."

Demography↗