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PubMed1999

[What shapes people's notions of health and illness?].

Lay conceptions of health are shaped by a variety of demographic, social, and personal factors. Research has focused on psychological and sociological perspectives, and three core models have dominated the field: the cognitive developmental model, the health locus of control model, and the so-called health belief model. Societal factors have been less studied. On the basis of a meta model we discuss how changes in prevalence of disease and disease panorama, social network, the experience of uncertainty, and the medical focus on risk may have impact on lay conceptions of health and disease. The joint effect of the medical focus on risk and disintegrating social networks seems to be the central force behind medicalization.

Attitude to Health↗
PubMed2005

Forest fragmentation predicts local scale heterogeneity of Lyme disease risk.

Fragmentation of the landscape has been proposed to play an important role in defining local scale heterogeneity in Lyme disease risk through influence on mammalian host density and species composition. We tested this observed relationship in a suburban region around Lyme, Connecticut, where we collected data on the density of the tick vector, Ixodes scapularis and prevalence of the Lyme bacterium, Borrelia burgdorferi at 30 sites. Analysis of the landscape pattern of forest patches was performed using satellite imagery. The calculated landscape indices, which included patch size and isolation, revealed a positive link between fragmentation and both tick density and infection prevalence in ticks. In spite of higher entomologic risk, human incidence of Lyme disease is lower in fragmented contexts suggesting that entomologic risk is not the critical driver of human infections. These results represent a departure from the prior claims that fragmentation and human Lyme disease risk are positively linked. A complete understanding of the influence of landscape fragmentation will allow for improved risk mapping and potential environmental management of Lyme disease.

Animals↗
PubMed2005

Extinction risk of a meta-population: aggregation approach.

Aggregation of variables of a complex mathematical model with realistic structure gives a simplified model which is more suitable than the original one when the amount of data for parameter estimation is limited. Here we explore use of a formula derived for a single unstructured population (canonical model) in predicting the extinction time for a population living in multiple habitats. In particular we focus multiple populations each following logistic growth with demographic and environmental stochasticities, and examine how the mean extinction time depends on the migration and environmental correlation. When migration rate and/or environmental correlation are very large or very small, we may express the mean extinction time exactly using the formula with properly modified parameters. When parameters are of intermediate magnitude, we generate a Monte Carlo time series of the population size for the realistic structured model, estimate the "effective parameters" by fitting the time series to the canonical model, and then calculate the mean extinction time using the formula for a single population. The mean extinction time predicted by the formula was close to those obtained from direct computer simulation of structured models. We conclude that the formula for an unstructured single-population model has good approximation capability and can be applicable in estimating the extinction risk of the structured meta-population model for a limited data set.

Animals↗
PubMed2002

Detection, characterization, and prediction of tick-borne disease foci.

Tick-borne disease (TBD) transmission foci need to be characterized in space and time, and are often discontinuous on both scales. An active TBD focus is dependent on the fulfillment of three conditions: tick survival, pathogen survival and opportunities for human exposure. The essentials for tick survival include food sources, reproduction, and protection from environmental extremes. The pathogen survival kit includes sufficient densities of ticks and suitable reservoir hosts, and opportunities for transmission between them in order to maintain infection. Opportunities for human exposure depend on sufficient number of encounters between ticks and humans. Because tick foci need to be described on a range of spatial and temporal resolutions, data for such characterization include a variety of surveillance data, field and laboratory experimental data, as well as results of statistical and mathematical analysis and modeling. The application of new tools from molecular biology, geographic information systems (GIS), and satellite imagery, in conjunction with appropriate analytical methods allow for detection of unknown foci and prediction of new ones. A long-term multi-scale study of Ixodes scapularis and Lyme disease in the north-central U. S. is reviewed. Diverse surveillance methods of ticks, rodents, deer, canids and humans were coupled with environmental characterization in situ to create a habitat profile for Lyme disease ticks. Incorporating various digitized databases, a statistical model was used to develop a risk map for tick distribution in the region. The process of introduction and establishment of new tick foci along the Illinois River is described in relation to the known tick distribution and predictions of invasion based on the risk model.

Animals↗
PubMedDate not supplied

[Results of specific neonatal screening for congenital dysplasia of the hip at the Vicenza Hospital. A prospective study of subjects at risk].

The aim of the study was to evaluate the incidence of pathological neonatal hips in the community served by the central Vicenza local health authority and to establish a protocol to minimize demands on available equipment, staff and the family. From May 1992 to May 1993 all neonates at San Bortolo Hospital in Vicenza were subjected to specific clinical examination of the hip by staff experienced in neonatal care. Neonates then underwent ultrasound examination--catalogued according to Graf--if they presented risk factors (dynamic ultrasound test was omitted). The orthopaedic examination was carried out in all cases. The total number of neonates involved was 1939 (994 m., 945 f.). Of these, 142 (7.3%) underwent ultrasonography (60 m., 82 f.). Family history and breech delivery were the most frequent anamnestic risk factors justifying ultrasound examination while among objective risk factors the most frequent being a clicking sound. Considering the clinical and ultrasound findings the resulting overall incidence of pathological hips is 0.25%. So far, there have been no late cases of c.d.h. A screening protocol such as ours cannot realistically aim to identify all pathological hips, however the great majority can be diagnosed at this early stage. Resources comparable to those used for our study are available to many other local health authorities. Higher diagnostic standard depend closely on local health policy.

Cohort Studies↗
PubMedDate not supplied

Demographic consequences of unpredictability in fertility outcomes.

Child survival is probabilistic, but the unpredictability in family formation and completed family size has been neglected in the fertility literature. In many societies, ending the family cycle with too few or too many surviving offspring entails serious social, economic, or fitness consequences. A model of risk- (or variance-) sensitive adaptive behavior that addresses long-term fertility outcomes is presented. The model shows that under conditions likely to be common, optimal, risk-sensitive reproductive strategies deviate systematically from the completed family size that would be expected if reproductive outcome is were predictable. This is termed the "variance compensation hypothesis." Variance compensation may be either positive or negative, resulting in augmented or diminished fertility. Which outcome obtained is a function of identifiable social, economic, and environmental factors. Through its effect on fertility behavior, variance compensation has a direct bearing on birth spacing and completed fertility, and thereby on problems in demography and human population biology ranging from demographic transitions to maternal depletion and child health. Risk-sensitive models will be a necessary component of a general theory of fertility.

Birth Rate↗
PubMed2002

Production of drinking water from raw water containing cyanobacteria--pilot plant studies for assessing the risk of microcystin breakthrough.

Toxins in cyanobacteria are a recognized risk in the treatment of drinking-water treatment. Cyanotoxins can occur in two modifications: cell bound and dissolved in water. The process of toxin release may occur naturally, but it also may be induced through the processes of drinking-water treatment. Both causes of release are relevant to the safety of drinking water. This study investigated cyanotoxin release and elimination through different treatment trains in systematic pilot-scale studies with water from the Weida Reservoir, in Thuringia, Germany. The Weida Reservoir is a dimictic mesoeutrophic reservoir typical for a number of mountainous areas in Europe, with Planktothrix rubescens as the dominant phytoplankton species, and shows a characteristic seasonal pattern of population development and microcystin occurrence. To assess the risk of microcystin breakthrough, the pilot-scale results as well as results of laboratory-scale experiments were used for developing a kinetic model of toxin release in relation to elimination. By calculating removal efficiency of total microcystins (cell bound and dissolved) for different treatment trains, raw water quality was related to the quality targets for finished water, and breakthrough risks could be calculated for given treatment trains and varying cyanobacterial population densities in the reservoir.

Cyanobacteria↗
PubMed2001

A comparison of biomarker responses in the earthworm Aporrectodea caliginosa to the organophosphorus insecticides diazinon and chlorpyrifos.

Three biomarkers in Aporrectodea caliginosa Savigny were evaluated for their ability to detect exposure to organophosphorus insecticides, and these physiological responses were related to effects on growth and life-table parameters. Adult and juvenile earthworms were exposed to a laboratory-simulated field rate (low concentration) and a higher sublethal concentration of diazinon and chlorpyrifos. After a four-week exposure, juveniles were evaluated for cholinesterase activity, glutathione S-transferase activity, and growth, and adults were evaluated for the lysosomal neutral red retention assay (NRRA) and growth. Cholinesterase activity and the NRRA were more sensitive than growth in each age group for detecting exposure to the pesticides. Life-table parameters were evaluated in earthworms exposed as juveniles and as adults. Maturation was less sensitive to pesticides than was cocoon production. Growth and cocoon production in earthworms exposed as juveniles appeared to be more sensitive to organophosphorus insecticides than earthworms exposed as adults. Life-table responses in juveniles may, therefore, be more predictive of long-term impacts of organophosphorus insecticide applications on populations than responses in adults. Biomarker responses occurred at similar or lower concentrations than those causing an adverse effect on cocoon production and cocoon viability, indicating their usefulness in risk assessment for predicting ecologically relevant assessment end points.

Age Factors↗
PubMed2001

Climatic effects on Salmonella survival in plant and soil irrigated with artificially inoculated wastewater: preliminary results.

The use of wastewater to replace other water resources for irrigation is highly dependent on whether the health risk and environmental impacts entailed are acceptable or not. Total count and species of microorganisms found in wastewater vary widely because of climatic conditions, season, population sanitary habits and disease incidence. Salmonella, one of the genera associated with waterborne diseases, lives in the intestine. Thus, it is widely accepted that they have a limited survival period under environmental conditions. Wastewater management practices and the ability of Salmonella to survival under field conditions would determine the health risk associated with its presence in wastewater. Although chlorination is widely used, there are situations in which Salmonella is able to survive the sudden stress imposed by this technique. The aim of this experiment was to contribute to the study of the climatic and soil effects on pathogen survival under agricultural field conditions in order to assess which were the best wastewater management practices from both health and economic points of view. Five pots filled with soil seeded with Medicago sativa and an automatic weather station were used. A secondary effluent was artificially inoculated with Salmonella. In addition, open plates (filled with sterilised soil) and ultraviolet radiation isolated plates (filled with non-sterilised soil) were used. As soil heat emission contributes to the environmental conditions around the bacteria, standardised meteorological temperature data had to be carefully used in the bacterial survival studies under agricultural conditions. Radiation was the main cause of Salmonella mortality as its effect was more important than natural soil bacteria competence. Higher reduction of Salmonella counts could have been associated with longer spring days. Soil was able to effectively remove Salmonella. Subsurface drip irrigation methods could provide an effective tool to prevent health risk associated with wastewater irrigation.

Agriculture↗
PubMed2001

Prediction of areas around the Mediterranean at risk of bluetongue by modelling the distribution of its vector using satellite imaging.

Bluetongue is an infectious disease of ruminants caused by a virus transmitted by biting midges, one species of which, Culicoides imicola, is the major vector in the Old World. Following an epizootic of African horse sickness,a related disease, in Iberia and Morocco between 1987 and 1991, C imicola was trapped for two years at 44 sites in the affected region and models were developed for predicting the abundance of C imicola at these sites. Discriminant analysis was applied to identify the best model of three levels of abundance from 40 Fourier-processed remotely sensed variables and a digital elevation model. The best model correctly predicted the abundance level at 41 of the 44 sites. The single most important variable was the phase of the annual cycle of the normalised difference vegetation index. The model was used to predict the abundances of C imicola elsewhere around the Mediterranean and predicted high levels of abundance in many areas recently affected by bluetongue, including the Balearics, Sardinia, Sicily, eastern Greece, western Turkey, Tunisia and northern Algeria. The model suggests that eastern Spain, the island of Ibiza, the provinces of Lazio and Puglia in Italy, the Peloponnese and parts of northern Algeria and Libya may be at risk of bluetongue in 2001.

Animals↗
PubMed1982

Residential mobility and urban-rural residence within life stages related to health risk and chronic disease in Tecumseh, Michigan.

Residential history, diagnosis of three chronic diseases, five clinical measurements and histories of smoking and drinking were obtained from a sample of 615 women and 529 men, aged 35-69, randomly selected from respondents of the Tecumseh Community Health Study. Two measures of residential mobility and one of urban-rural residence, during early life stages and over the entire lifetime, were related to subsequent adult health traits. Greater residential mobility, particularly in childhood but also in later life, was significantly associated with greater prevalence of hypertension and higher mean diastolic blood pressure in older persons. Greater duration of urban residence was associated with greater prevalence of chronic bronchitis. Both residential traits were associated with greater prevalence of CHD, and with behavior patterns, namely cigarette smoking and drinking, that are risk factors for certain chronic diseases.

Adult↗
PubMed2003

Improving risk adjustment for Medicare capitated reimbursement using nonlinear models.

OBJECTIVES: This article compares a linear risk-adjusted model of medical expenditures for Medicare patients with a model that explicitly account for skewness in distribution of expenditures. METHODS: A model of expenditures and a model of the square root of expenditures, each expressed as linear combinations of risk adjusters, are estimated using data from the 1992 through 1994 Medicare Current Beneficiary Surveys. Five sets of risk adjusters are considered. Each combination of model and set of risk adjusters is tested for linearity, heteroscedasticity, in-sample fit (R2), forecast performance (forecast bias and forecast mean squared error), and overfitting the data. We analyze forecast performance (1)based on forecasts in same year used for estimation, and (2)based on forecasts in the year following that used for estimation. RESULTS: In the first analysis, the model using a square root transformation of expenditures as the dependent variable and the more parsimonious specification of risk adjusters performs best in terms of forecast squared error and overfitting. The untransformed model performs best in terms of forecast bias in each group based on severity of disability, with the exception of the severely disabled for whom the square root model is best. In the second analysis, the square root model performs better than the untransformed model in terms of forecast squared error, but neither model is statistically distinguishable from zero in terms of bias. CONCLUSIONS: Accounting for skewness in expenditures tends to improve precision but not necessarily bias, except among the severely disabled. Adjusting for health status improves risk adjustment.

Activities of Daily Living↗
PubMed2002

The relation between lysosomal biomarker and population responses in a field population of Microchaetus sp. (oligochaeta) exposed to the fungicide copper oxychloride.

The ecological relevance of the neutral red retention assay as a biomarker in an indigenous earthworm population (Microchaetus sp.) exposed to the fungicide copper oxychloride was investigated. Changes in earthworm biomass and numbers were monitored and related to changes in neutral red retention times of coelomocytes as well as changes in copper concentrations in the soil and earthworm body tissues. Results indicated that Microchaetus sp. responded sensitively to the copper oxychloride by showing an initial decrease in biomass 2 months after spraying started. This was followed by a significant decrease in worm numbers after 3 months. The neutral red retention times of earthworm coelomocytes decreased significantly within the first month of treatment and correspond to a significant increase in soil copper concentrations, but not with an immediate increase in body burdens of copper. More than a year after spraying had stopped the worm biomass and numbers were still significantly lower in the treated plots compared with the control plots. Since the reduction in neutral red retention times could be attributed to the presence of copper oxychloride and preceded the decline in population density and biomass, we conclude that this biomarker has a useful role to play in environmental risk assessment and could provide a warning of impending ecological damage.

Animals↗
PubMed2005

Gull eggs--food of high organic pollutant content?

A wide range and occasionally high levels of persistent organic pollutants (POPs) are reported in Arctic regions, especially among top predators. Polar bears (Ursus maritimus), arctic foxes (Alopex lagopus) and some gull species (Larus spp.) often have high levels of these fat-soluble pollutants. Gulls deposit significant levels of these contaminants in their eggs. In northern regions, gull eggs are part of the traditional human diet. In the present study we have investigated the levels of POPs in gull eggs in order to determine the tolerable weekly intake (TWI) for humans. Concentrations of polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) were measured in 214 gull eggs collected in the spring of 2001-02. The eggs were collected from four gull species (herring gulls (Larus argentatus), great black-backed gulls (L. marinus), lesser black-backed gulls (L. fuscus) and glaucous gulls (L. hyperboreus)) at 12 different locations in Northern Norway, on the Faroe Islands and on Svalbard. The pollutant levels in gull eggs were found to be 65.5 +/- 26.9 pg toxic equivalent (TE) for dioxin and PCB g(-1) wet weight. Based on these findings and the TWI-value determined by the EU Scientific Committee on Food it is advised that children, young women and pregnant and nursing women should not eat gull eggs. Other people should limit their intake of eggs to an absolute minimum, considering the health risks associated with gull egg intake.

Animals↗
PubMed2002

Assessing human health response in life cycle assessment using ED10s and DALYs: part 1--Cancer effects.

Life cycle assessment (LCA) is a framework for comparing products according to their total estimated environmental impact, summed over all chemical emissions and activities associated with a product at all stages in its life cycle (from raw material acquisition, manufacturing, use, to final disposal). For each chemical involved, the exposure associated with the mass released into the environment, integrated over time and space, is multiplied by a toxicological measure to estimate the likelihood of effects and their potential consequences. In this article, we explore the use of quantitative methods drawn from conventional single-chemical regulatory risk assessments to create a procedure for the estimation of the cancer effect measure in the impact phase of LCA. The approach is based on the maximum likelihood estimate of the effect dose inducing a 10% response over background, ED10, and default linear low-dose extrapolation using the slope betaED10 (0.1/ED10). The calculated effects may correspond to residual risks below current regulatory compliance requirements that occur over multiple generations and at multiple locations; but at the very least they represent a "using up" of some portion of the human population's ability to accommodate emissions. Preliminary comparisons are performed with existing measures, such as the U.S. Environmental Protection Agency's (U.S. EPA's) slope factor measure q1*. By analyzing bioassay data for 44 chemicals drawn from the EPA's Integrated Risk Information System (IRIS) database, we explore estimating ED10 from more readily available information such as the median tumor dose rate TD50 and the median single lethal dose LD50. Based on the TD50, we then estimate the ED10 for more than 600 chemicals. Differences in potential consequences, or severity, are addressed by combining betaED10 with the measure disability adjusted life years per affected person, DALYp. Most of the variation among chemicals for cancer effects is found to be due to differences in the slope factors (betaED10) ranging from 10(-4) up to 10(4) (risk of cancer/mg/kg-day).

Carcinogens, Environmental↗