Esra Ozdenerol

Comparison of spatial scan statistic and spatial filtering in estimating low birth weight clusters

BackgroundThe purpose of this study is to examine the spatial and population (e.g., socio-economic) characteristics of low birthweight using two different cluster estimation techniques. We compared the results of Kulldorffs Spatial Scan Statistic with the results of Rushtons Spatial filtering technique across increasing sizes of spatial filters (circle). We were able to demonstrate that varying approaches exist to explore spatial variation in patterns of low birth weight.ResultsSpatial filtering results did not show any particular area that was not statistically significant based on SaTScan. The high rates, which remain as the filter size increases to 0.4, 0.5 to 0.6 miles, respectively, indicate that these differences are less likely due to chance. The maternal characteristics of births within clusters differed considerably between the two methods. Progressively larger Spatial filters removed local spatial variability, which eventually produced an approximate uniform pattern of low birth weight.ConclusionSaTScan and Spatial filtering cluster estimation methods produced noticeably different results from the same individual level birth data. SaTScan clusters are likely to differ from Spatial filtering clusters in terms of population characteristics and geographic area within clusters. Using the two methods in conjunction could provide more detail about the population and spatial features contained with each type of cluster.

Locating suitable habitats for West Nile Virus-infected mosquitoes through association of environmental characteristics with infected mosquito locations: a case study in Shelby County, Tennessee

BackgroundSince its first detection in 2001, West Nile Virus (WNV) poses a significant health risk for residents of Shelby County in Tennessee. This situation forced public health officials to adopt efficient methods for monitoring disease spread and predicting future outbreaks. Analyses that use environmental variables to find suitable habitats for WNV-infected mosquitoes have the potential to support these efforts. Using the Mahalanobis Distance statistic, we identified areas of Shelby County that are ecologically most suitable for sustaining WNV, based on similarity of environmental characteristics to areas where WNV was found. The environmental characteristics in this study were based on Geographic Information Systems (GIS) data, such as elevation, slope, land use, vegetation density, temperature, and precipitation.ResultsOur analyses produced maps of likely habitats of WNV-infected mosquitoes for each week of August 2004, revealing the areas that are ecologically most suitable for sustaining WNV within the core of the Memphis urban area. By comparing neighbourhood social characteristics to the environmental factors that contribute to WNV infection, potential social drivers of WNV transmission were revealed in Shelby County. Results show that human population characteristics and housing conditions such as a high percentage of black population, low income, high rental occupation, old structures, and vacant housing are associated with the focal area of WNV identified for each week of the study period.ConclusionWe demonstrated that use of the Mahalanobis Distance statistic as a similarity index to assess environmental characteristics is a potential raster-based approach to identify areas ecologically most suitable for sustaining the virus. This approach was also useful to monitor changes over time for likely locations of infected mosquito habitats. This technique is very helpful for authorities when making decisions related to an integrated mosquito management plan and targeted health education outreach.

Assessing the impact of the local environment on birth outcomes: a case for HLM.

Hierarchical linear Models (HLM) is a useful way to analyze the relationships between community level environmental data, individual risk factors, and birth outcomes. With HLM we can determine the effects of potentially remediable environmental conditions (e.g., air pollution) after controlling for individual characteristics such as health factors and socioeconomic factors. Methodological limitations of ecological studies of birth outcomes and a detailed analysis of the varying models that predict birth weight will be discussed. Ambient concentrations of criterion air pollutants (e.g., lead and sulfur dioxide) demonstrated a sizeable negative effect on birth weight; while the economic characteristics of the mothers residential census tract (ex. poverty level) also negatively influenced birth weight.

Exploring the Spatio-Temporal Dynamics of Reservoir Hosts, Vectors, and Human Hosts of West Nile Virus: A Review of the Recent Literature

Over the last two decades West Nile Virus (WNV) has been responsible for significant disease outbreaks in humans and animals in many parts of the World. Its extremely rapid global diffusion argues for a better understanding of its geographic extent. The purpose of this inquiry was to explore spatio-temporal patterns of WNV using geospatial technologies to study populations of the reservoir hosts, vectors, and human hosts, in addition to the spatio-temporal interactions among these populations. Review of the recent literature on spatial WNV disease risk modeling led to the conclusion that numerous environmental factors might be critical for its dissemination. New Geographic Information Systems (GIS)-based studies are monitoring occurrence at the macro-level, and helping pinpoint areas of occurrence at the micro-level, where geographically-targeted, species-specific control measures are sometimes taken and more sophisticated methods of surveillance have been used.

Pathogenic Role of Environmental Toxins in Immune-Mediated Liver Diseases

Immune-mediated liver diseases contribute significantly to morbidity and mortality due to liver failure and the need for liver transplantation. The pathogenesis of the immune-mediated chronic liver diseases, primary sclerosing cholangitis, autoimmune hepatitis, and primary biliary cirrhosis, is poorly understood. Genetic susceptibility factors may play a role, but increasing attention is being given to the association between environmental factors and these diseases. The existence of such a relationship is supported by epidemiologic surveys, animal models, and geographic clustering analyses. Unearthing the cause of this association may provide insight into the pathogenesis of immune-mediated chronic liver diseases and autoimmunity.

Exploring Childhood Lead Exposure through GIS: A Review of the Recent Literature

Childhood exposure to lead remains a critical health control problem in the US. Integration of Geographic Information Systems (GIS) into childhood lead exposure studies significantly enhanced identifying lead hazards in the environment and determining at risk children. Research indicates that the toxic threshold for lead exposure was updated three times in the last four decades: 60 to 30 micrograms per deciliter (µg/dL) in 1975, 25 µg/dL in 1985, and 10 µb/dL in 1991. These changes revealed the extent of lead poisoning. By 2012 it was evident that no safe blood lead threshold for the adverse effects of lead on children had been identified and the Center for Disease Control (CDC) currently uses a reference value of 5 µg/dL. Review of the recent literature on GIS-based studies suggests that numerous environmental risk factors might be critical for lead exposure. New GIS-based studies are used in surveillance data management, risk analysis, lead exposure visualization, and community intervention strategies where geographically-targeted, specific intervention measures are taken.

GIS and Remote Sensing Use in the Exploration of Lyme Disease Epidemiology.

Given the relatively recent recognition of Lyme disease (LD) by CDC in 1990 as a nationally notifiable infectious condition, the rise of reported human cases every year argues for a better understanding of its geographic scope. The aim of this inquiry was to explore research conducted on spatiotemporal patterns of Lyme disease in order to identify strategies for implementing vector and reservoir-targeted interventions. The focus of this review is on the use of GIS-based methods to study populations of the reservoir hosts, vectors and humans in addition to the spatiotemporal interactions between these populations. New GIS-based studies are monitoring occurrence at the macro-level, and helping pinpoint areas of occurrence at the micro-level, where spread within populations of reservoir hosts, clusters of infected ticks and tick to human transmission may be better understood.

Predictors of functional limitation trajectories after injury in a nationally representative U.S. older adult population

PURPOSE Studies examining postinjury functional status have demonstrated that individuals with severe injuries often do not return to baseline levels of physical functioning. We sought to investigate the impact injuries have on changes in physical functioning across the life course of older adults. The studys objectives were to (1) identify trajectories of long-term functional limitations after injury in the older adult population to better characterize the recovery process and (2) predict which individuals are most at risk for poor functional trajectories after injury. METHODS A retrospective cohort study was conducted using six waves of data from the Health and Retirement Study, which surveys Americans older than 50 years every two years. A group-based trajectory model was used to identify trajectories of functional limitations in injured participants. Using multivariate regression, we identified significant predictors of each trajectory. RESULTS Five distinct trajectories were identified: Trajectory 1--consistently low functional limitations scores (18.9%), Trajectory 2--increase in functional limitations after injury followed by a gradual, incomplete recovery (46.3%), Trajectory 3--increase in functional limitations followed by further decline in functioning (10.5%), Trajectory 4--increase in functional limitations after injury followed by a gradual, complete recovery (13.4%), and Trajectory 5--consistently high functional limitations scores (10.8%). Gender, multiple health conditions, and insurance status predicted trajectory membership. CONCLUSIONS Functional limitations after injury follow distinct trajectories that can be predicted by baseline individual characteristics.

DETECTING SPATIAL CLUSTERS OF CANCER MORTALITY IN EAST BATON ROUGE PARISH, LOUISIANA

According to the Louisiana State Center for Health Statistics (1998), overall age-adjusted mortality rates for Louisiana’s major causes of death over the past five years indicate an increase in cancer-related deaths. This has generated great concern from the citizens in the state. In East Baton Rouge Parish, questions were raised on whether the heavy petrochemical industry, increased air pollution, increased population growth, and increased need for transportation were related to the increase in cancer-related deaths. Before an intense epidemiological study is launched, a key question will need to be answered: do these cancer deaths tend to concentrate spatially? If so, where are the clusters and what characterize them? If significant spatial clusters are identified, then further in-depth epidemiological studies can be conducted to investigate what causes these clusters. On the contrary, if no significant clusters are found, further in-depth investigation may be useless. Therefore, spatial techniques that measure the spatial structure of cancer patterns and detect clusters can be a useful surveillance or hypothesis-generating tool for environmental and public health investigations.