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At least 109 records · Page 6Linked to original sources

PubMed2002

Rise in malaria incidence rates in South Africa: a small-area spatial analysis of variation in time trends.

Using Bayesian statistical models, the authors investigated spatial and temporal variations in small-area malaria incidence rates for the period mid-1986 to mid-1999 for two districts in northern KwaZulu Natal, South Africa. Maps of spatially smoothed incidence rates at different time points and spatially smoothed time trends in incidence gave a visual impression of the highest increase in incidence occurring where incidence rates previously had been lowest. This was confirmed by conditional autoregressive models, which showed that there was a significant negative association between time trends and smoothed baseline incidence before the steady rise in caseloads began. Growth rates also appeared to be higher in the areas close to the Mozambican border. The main findings of this analysis were that: 1) the spatial distribution of the rise in malaria incidence is uneven and strongly suggests a geographic expansion of high-malaria-risk areas; 2) there is evidence of a stabilization of incidence in areas that had the highest rates before the current escalation of rates began; and 3) areas immediately adjoining the Mozambican border appear to have undergone larger increases in incidence, in contrast to the general pattern of low growth in the more northern, high-baseline-incidence areas, but this was not confirmed by modeling. Smoothing of small-area maps of incidence and growth in incidence (trend) is important for interpretation of the spatial distribution of disease incidence and the spatial distribution of rapid changes in disease incidence.

Bayes Theorem↗

PubMed2004

Spatial analysis of the distribution of intestinal nematode infections in Uganda.

The spatial epidemiology of intestinal nematodes in Uganda was investigated using generalized additive models and geostatistical methods. The prevalence of Ascaris lumbricoides and Trichuris trichiura was unevenly distributed in the country with prevalence greatest in southwest Uganda whereas hookworm was more homogeneously distributed. A. lumbricoides and T. Trichiura prevalence were nonlinearly related to satellite sensor-based estimates of land surface temperature; hookworm was nonlinearly associated with rainfall. Semivariogram analysis indicated that T. trichiura prevalence exhibited no spatial structure and that A. lumbricoides exhibited some spatial dependency at small spatial distances, once large-scale, mainly environmental, trends had been removed. In contrast, there was much more spatial structure in hookworm prevalence although the underlying factors are at present unclear. The implications of the results are discussed in relation to parasite spatial epidemiology and the prediction of infection distributions.

Adolescent↗

PubMed2003

Tuberculosis transmission patterns in a high-incidence area: a spatial analysis.

SETTING: In the Cape Town suburbs of Ravensmead and Uitsig, tuberculosis has reached epidemic levels, with notifications of 1340/100,000 in 1996. These suburbs are characterised by overcrowding, high unemployment and poverty. It is traditionally believed that tuberculosis transmission takes place mainly in households after close contact with an infectious person. Studies have recently linked tuberculosis transmission to locations outside the household, and have associated these places with a particular high-risk lifestyle. Anthropological studies in some suburbs of Cape Town, in which a very high number of local drinking places (shebeens) were identified (17 per km2), have suggested that social drinking is part of such a lifestyle. OBJECTIVE: To investigate various risk factors and places of transmission of tuberculosis using a geographical information system (GIS). RESULTS AND CONCLUSION: The 1128 bacteriologically-proven cases of tuberculosis studied over the period 1993-1998 were investigated using spatial epidemiological techniques of exploratory disease mapping. Point pattern analysis and spatial statistics indicated clustering of cases in the areas of high incidence. Significant associations of tuberculosis notifications were found with unemployment, overcrowding and number of shebeens per enumerator sub-district. High tuberculosis notifications with unemployment and its associated poverty emerged as the strongest association.

Adult↗

PubMed1996

Temporal and spatial analysis of potential maps via multiresolution decompositions.

Cardiac potentials recorded on the epicardium or the body surface by an array of electrodes are usually analyzed either as spatial distributions or temporal waveforms. Thus, the analysis often involves temporal descriptors (eg. max dV/dt) or spatial descriptors (eg. location of local extrema) only. The best known transform technique that has been applied to these data that combines both spatial and temporal characteristics is the Karhunen-Loeve transform, a global transform applied to temporal and/or spatial bases obtained by statistical analysis of a database. As an alternative, multiresolution decompositions and related wavelet-type transforms have recently seen great development in signal processing and related fields. They offer flexibility, employing transformations onto local (rather than global) and fixed (rather than data-dependent) databases, and allow transformation of distributions, waveforms, or both, as desired. The utility of this method as applied to temporal and spatial segmentation and analysis of map data from both epicardial plaques and body surface potentials recorded during percutaneous transluminal coronary angioplasty is illustrated.

Body Surface Potential Mapping↗

PubMedDate not supplied

From porous media to trabecular bone relaxation analysis: spatial variation of marrow 1H relaxation time distributions detected in vitro by quasi-continuous distribution analysis.

Quasi-continuous distributions of T(1) and T(2) of 1H nuclei were analyzed in vitro at 20MHz on some twenty fresh bone samples of pig femur. Large numbers of data points allowed a detailed investigation. Relaxation data were inverted by UPEN (Uniform PENalty inversion). In all samples the widths of the distributions, covering more than two decades, are not even close to being compatible with single exponential components. Moreover, the T(1) and T(2) distributions show enough character to distinguish the samples. We observe a spatial variation of these characteristics and in particular a second peak centered at 500-600 ms appearing in some proximal femur samples. The quasi-continuous distribution allows one to correlate the water content of the sample with parts of the distributions in specific time ranges. The signal fraction with T(1) values longer than a cutoff time of about 170 ms is in very good agreement with the water content of the samples and is significantly larger in the group of samples cored from proximal femur. Also T(2) distributions differentiate the samples, and the signal fraction with T(2) shorter than about 30 ms is significantly larger in the group of distal femur samples.

Animals↗

PubMedDate not supplied

Spatial analysis of within-population microsatellite variability reveals restricted gene flow in the Pacific golden chanterelle (Cantharellus formosus).

We examined the within-population genetic structure of the Pacific golden chanterelle (Cantharellus formosus) in a 50 y old forest stand dominated by Douglas-fir (Pseudotsuga menziesii) and western hemlock (Tsuga heterophylla) with spatial autocorrelation analysis. We tested the null hypothesis that multilocus genotypes possessed by chanterelle genets were randomly distributed within the study area. Fruit bodies from 203 C. formosus genets were collected from a 50 ha study plot. One hundred six unique multilocus genotypes were identified after scoring these collections at five microsatellite loci. Statistically significant positive spatial autocorrelation was detected indicating the presence of fine-scale genetic structure within the area. Repeated autocorrelation analyses with varied minimum distance classes (50-500 m) detected positive spatial genetic structure up to 400 m. Therefore nonrandom evolutionary processes (e.g., isolation by distance) can cause fine-scale genetic structure in C. formosus. The implications of this research for future broad-scale population studies of this species are that population samples should be separated by at least 400 m to be considered statistically independent. Sampling designs that account for fine-scale genetic structure will better characterize heterogeneity distributed across the landscape by avoiding the effects of pseudo replication.

Basidiomycota↗

PubMed2005

Mapping and visualizing the location HIV service providers: an exploratory spatial analysis of Toronto neighborhoods.

Efforts have been made to identify, reduce and ultimately eliminate health disparities, yet variation in access to health services continues to be an important concern. As with large American cities, Toronto has been particularly hard hit by the AIDS epidemic, representing 68% of Ontario's HIV diagnoses (Health Canada, 2000). The accessibility of healthcare in terms of the geographic location and spatial distribution of health services are important factors in healthcare utilization. In this descriptive paper we map the location of HIV-related services and use exploratory spatial data analysis to visualize and examine the distribution of HIV service providers. In examining the location of HIV service providers we map the minimum distance to the nearest service provider. Our analyses also map and analyze five separate categories of HIV-related services. These include: (1) Diagnostic and preventive services; (2) Health and social services for initial HIV diagnosis; (3) Emotional and social support; (4) Emergency services; and (5) Medical and end-of-life services. While our findings point to significant clustering of some types of HIV-related services (such as emergency and preventive services), other services are more evenly distributed across Toronto (this includes medical and end-of-life services). Our findings point to the need for policy makers and researchers to integrate mapping, GIS and spatial analytic techniques into their analyses of the neighborhoods and subsequently the populations in those neighborhoods that are underserved in terms of accessibility of some categories of HIV-related services.

Community Health Services↗

PubMed1985

Corticocortical efferent systems in the monkey: a quantitative spatial analysis of the tangential distribution of cells of origin.

The laminar and tangential distributions of association neurons projecting from areas 4 and 6 of the frontal lobe to area 5 of the superior parietal lobule were studied in macaque monkeys by using horseradish peroxidase histochemistry. In both areas 4 and 6 association neurons were medium-large pyramidal cells of layers II and III, and pyramidal and fusiform cells of layers V-VI. Tangentially, they were distributed unevenly over the cortical surface occupying only certain parts of areas 4 and 6, including the dorsomedial part of area 6, the proximal arm region of Woolsey's M1 map, parts of the postarcuate cortex, and the supplementary motor area. Within these projection zones, the number of projection cells waxed and waned in a periodic fashion. Quantitative methods, including spectral analysis techniques, were used to characterize precisely spatial periodicities along the rostrocaudal dimension. The same quantitative analyses were used to determine the nature of the tangential distribution of corticocallosal cells of area 5 projecting to contralateral area 5. Both association and callosal spectra contained a strong component in the range of low spatial frequencies, corresponding to periods greater than 2 mm. Moreover, a consistent peak was observed in both spectra at spatial frequencies corresponding to periods ranging from 0.85 to 1.28 mm. This peak is in accord with the hypothesis of a modular organization of the cells of origin of these projection systems.

Animals↗

PubMed2000

Monitoring insect pests in retail stores by trapping and spatial analysis.

Stored-product insects are a perennial problem in retail stores, where they damage and contaminate susceptible merchandise such as food products and animal feed. Historically, pest management in these stores has relied heavily on chemical insecticides, but environmental and health issues have dictated use of safer methods, and these require better monitoring. A monitoring procedure that employs an array of moth and beetle traps combined with spatial (contour) analysis of trap catch was tested in three department stores and two pet stores. The rate of capture increased with the level of infestation but was essentially constant over 4- to 5-d trapping periods. Contour analysis effectively located foci of infestation and reflected population changes produced by applications of the insect growth regulator (S)-hydroprene. The most abundant insects were Plodia interpunctella (Hiibner), Lasioderma serricorne (F.), Oryzaephilus mercator (Fauvel), Tribolium castaneum (Herbst), and Cryptolestes pusillus (Schönherr). The results indicate that contour analysis of trap counts provides a useful monitoring tool for management of storage pests in retail stores. It identifies trouble spots and permits selection, timing, and precision targeting of control measures to achieve maximum pest suppression with minimum pesticide risk. It permits managers and pest control operators to visualize pest problems over an entire store, to monitor changes over time, and to evaluate the effectiveness of control intervention. The contour maps themselves, along with records of control applications and stock rotation, provide permanent documentation of pest problems and the effectiveness of pest management procedures.

Animals↗

PubMed2002

Spatial analysis to identify differentials in dental needs by area-based measures.

OBJECTIVES: To examine the association between tooth decay and dental treatment needs in 5-12-year-old schoolchildren in São Paulo with area-level indicators of social development. METHODS: The present study refers to a representative sample of children from the city of São Paulo, Brazil, comprising 2491 girls and boys attending public and private schools in different areas of the city. The assessment of caries and treatment needs followed the international methodological standards prescribed by the World Health Organization. We used spatial data analysis to describe epidemiological measures distributed by small areas, and to explore hypotheses of ecological association between caries indexes and indicators of social development. RESULTS: Schoolchildren in central districts were less affected by tooth decay and presented fewer dental treatment needs when compared to those in peripheral deprived areas. At the spatial level, average family income, unemployment rate, household overcrowding, and an index of inequality of income distribution were significantly correlated with variables measuring children's caries experience. CONCLUSIONS: The heterogeneous distribution of caries indexes by areas of the city indicates higher levels of dental decay in areas of social deprivation. The delimitation of areas with increased risk of caries and greater dental treatment needs should be helpful to public health services for the formulation of policies and the targeting of resources to address these problems.

Brazil↗

PubMed2004

Spatial analysis of body mass index and smoking behavior among WISEWOMAN participants.

BACKGROUND: The WISEWOMAN program focuses on reducing cardiovascular disease (CVD) risk factors by providing screening and lifestyle interventions for many low-income and uninsured women. To provide the most effective interventions possible, it is important to understand the characteristics of WISEWOMAN participants and their communities. METHODS: We used baseline data collected for WISEWOMAN participants from five states (Connecticut, Michigan, Nebraska, North Carolina, and South Dakota) who had enrolled in WISEWOMAN between January 2001 and December 2002 in order to examine body mass index (BMI) and smoking behavior for evidence of spatial clustering. We then examined whether neighborhood characteristics in clusters of high-risk factors differed from neighborhood characteristics in other locations. RESULTS: Six percent of the WISEWOMAN participants lived in ZIP codes with high-BMI clusters, and 4% lived in ZIP codes with high-smoking clusters. High-BMI and high-smoking clusters occurred, however, in different locations from each other. The high-BMI-clustered ZIP codes were, on average, located in more disadvantaged areas. Most of the differences between the high-smoking-clustered ZIP codes and the remaining ZIP codes were not statistically significant. CONCLUSIONS: Our analysis revealed spatial clustering in CVD risk factors among WISE-WOMAN participants. We also found evidence of a correlation between high-BMI clusters and low socioeconomic status of the surrounding community. A more in-depth analysis of the relationship between risk factors (e.g., BMI) and community characteristics in clustered locations will provide further information concerning the role of the community in affecting individual behavior and should allow for tailoring interventions to reduce these risk factors more effectively.

Adult↗

PubMed1995

Spatial analysis of Honolulu motor vehicle crashes: II. Zonal generators.

The spatial relationship between activities which generate trips and motor vehicle accidents is examined and applied to the City and County of Honolulu for 1990. A method is described for examining spatial variations in motor vehicle accidents, aggregated into small geographical areas. A spatial lag model is developed which examines the zonal relationship of motor vehicle accidents to population, employment and road characteristics. The resulting model is tested for each hour of the day, weekdays and weekends separately. The predictors of accidents fluctuate according to different trip generating activities and change considerably over the day. The method can generate expected accidents, allowing for an identification of areas which have higher than expected levels. It is argued that this method focuses attention on characteristics of neighborhoods and areas, and not just on the road system.

Accidents, Traffic↗

PubMed1986

Hemispheric laterality for spatial analysis in children with reading problems.

Lateralisation for tactile-spatial perception was studied in 21 10- to 15-yr.-old boys of average intelligence who were underachieving in reading and 21 matched controls. Controls showed a significant advantage at recognising shapes on a visual display when they had been actively felt with the left hand. There was no difference between left- and right-hand scores in the poor readers. This supports Witelson's (1977) finding that poor readers are less lateralised for spatial-processing than are average readers.

Child↗

PubMed2001

High resolution spatial analysis of plant systems.

Analysis of organisms using techniques that provide high spatial and temporal resolution is of increasing interest in many disciplines of biomedical research. Although the examination of animal tissues has been the main focus to date, the recent development and improvement of methods for the sampling and handling of single cells and for their biochemical analysis now provide tools for investigating plant as well as animal cells.

Biochemistry↗

PubMed2006

Spatial analysis of land use impact on ground water nitrate concentrations.

In spatial analyses of causes or health effects of environmental pollutants, small units of analyses are usually preferred for internal environmental homogeneity reasons but can only be done when fine resolution data are available for most units. Objectives of this study were to determine which land use practices were spatially associated with ground water nitrate concentrations across Prince Edward Island (PEI), Canada, and which spatial aggregation is the preferred unit of analyses. Nitrate concentrations were determined for 4855 samples from private wells. Validated field-by-field land use data were available. Average nitrate concentration and percentage of area for the 14 major land use categories in PEI were determined for each of three spatial aggregations: watersheds based on topography and hydrology; freeform polygon boundaries based on similar neighboring nitrate concentrations; and 500-m buffer zones around each well. Results showed that the percentages of potato, grain, and hay coverage were positive predictors of ground water nitrate concentrations. Percentage of blueberry was a marginally significant negative predictor in the watershed and freeform polygon models, and percentage of residential coverage was a positive predictor in the freeform polygon and buffer zone models. Spatial autocorrelation was present in the freeform polygon and buffer zone models even after land use was taken into account. In conclusion, analyses based on watersheds produced the best predictive model with the percentages of land cover of potato, hay, and grain being significantly associated with ground water nitrate concentrations, and the percentages of blueberry, clear-cut woodland, and other agriculture being marginally significant.

Agriculture↗

PubMedDate not supplied

Spatial analysis of news sources.

People in different places talk about different things. This interest distribution is reflected by the newspaper articles circulated in a particular area. We use data from our large-scale newspaper analysis system (Lydia) to make entity datamaps, a spatial visualization of the interest in a given named entity. Our goal is to identify entities which display regional biases. We develop a model of estimating the frequency of reference of an entity in any given city from the reference frequency centered in surrounding cities, and techniques for evaluating the spatial significance of this distribution.

Journal Article↗

PubMed2002

A method for spatial analysis of risk in a population-based case-control study.

Spatial distributions of disease occurrence and risk have traditionally served as a tool for identifying exposures of public health concern. Current software for manipulating geographic data (GIS) now allows many kinds of analyses not feasible before. This paper presents a method for producing a "picture" of disease risks based on residential history data from a population based case-control study. We illustrate the method using geographically coded data on individual-level risk factors, such as age and smoking, from a cancer study of the Upper Cape Cod region of Massachusetts for 1983-1986. Our results show the association between lung cancer and residential location as an indicator of exposure. Crude and adjusted odds ratios were estimated by adaptive rate stabilization and mapped using kriging as an interpolation method to examine the risk of lung cancer in the region. The crude and adjusted surfaces for various smoothing parameters were compared to identify areas of increased lung cancer not explained by standard risk factors. Such spatial patterns of disease risk may provide clues to exposures of importance or confirm associations with previously suspected exposures.

Adult↗

PubMed1998

Landscape ecology and epidemiology of vector-borne diseases: tools for spatial analysis.

Geographic information systems (GIS), global positioning systems (GPS), remote sensing, and spatial statistics are tools to analyze and integrate the spatial component in epidemiology of vector-borne disease into research, surveillance, and control programs based on a landscape ecology approach. Landscape ecology, which deals with the mosaic structure of landscapes and ecosystems, considers the spatial heterogeneity of biotic and abiotic components as the underlying mechanism which determines the structure of ecosystems. The methodologies of GIS, GPS, satellite imagery, and spatial statistics, and the landscape ecology--epidemiology approach are described, and applications of these methodologies to vector-borne diseases are reviewed. Collaborative studies by the author and colleagues on malaria in Israel and tsetse flies in Kenya, and Lyme disease, LaCrosse encephalitis, and eastern equine encephalitis in the north-central United States are presented as examples for application of these tools to research and disease surveillance. Relevance of spatial tools and landscape ecology to emerging infectious diseases and to studies of global change effects on vector-borne diseases are discussed.

Animals↗