Nikolaos Yiannakoulias

The high risk of stroke immediately after transient ischemic attack A population-based study

Background: The risk of stroke is elevated in the first 48 hours after TIA. Previous prognostic models suggest that diabetes mellitus, age, and clinical symptomatology predict stroke. The authors evaluated the magnitude of risk of stroke and predictors of stroke after TIA in an entire population over time. Methods: Administrative data from four different databases were used to define TIA and stroke for the entire province of Alberta for the fiscal year (April 1999–March 2000). The age-adjusted incidence of TIA was estimated using direct standardization to the 1996 Canadian population. The risk of stroke after a diagnosis of TIA in an Alberta emergency room was defined using a Kaplan-Meier survival function. Cox proportional hazards modeling was used to develop adjusted risk estimates. Risk assessment began 24 hours after presentation and therefore the risk of stroke in the first few hours after TIA is not captured by our approach. Results: TIA was reported among 2,285 patients for an emergency room diagnosed, age-adjusted incidence of 68.2 per 100,000 population (95% CI 65.3 to 70.9). The risk of stroke after TIA was 9.5% (95% CI 8.3 to 10.7) at 90 days and 14.5% (95% CI 12.8 to 16.2) at 1 year. The risk of combined stroke, myocardial infarction, or death was 21.8% (95% CI 20.0 to 23.6) at 1 year. Hypertension, diabetes mellitus, and older age predicted stroke at 1 year but not earlier. Conclusions: Although stroke is common after TIA, the early risk is not predicted by clinical and demographic factors. Validated models to identify which patients require urgent intervention are needed.

Utilization of health services following spinal cord injury: a 6-year follow-up study

Study design: Cohort study with 6-years follow-up.Objective: To describe the utilization of health services by persons with spinal cord injury (SCI) and compare it with that of the general population.Setting: Alberta, Canada.Methods: All persons who sustained an SCI in Alberta between April 1992 and March 1994 were followed from date of injury to 6 years postinjury. Cases were matched (1:5) with controls randomly selected from the general population and matched for age, gender, and region of residence. Administrative data from centralized health care databases were compiled to provide a complete picture of health care use, including hospitalizations, physician contacts, long-term care admissions, home care services, and the occurrence of secondary complications.Results: In all, 233 individuals with SCI and 1165 matched controls were followed for 6 years. Compared with the control group, persons with SCI were rehospitalized 2.6 times more often, spent 3.3 more days in hospital, were 2.7 times more likely to have a physician contact, and required 30 times more hours of home care services. Of those with SCI, 47.6% were treated for a urinary tract infection, 33.8% for pneumonia, 27.5% for depression, and 19.7% for decubitus ulcer.Conclusion: SCI places a heavy burden on the health care system. Persons with SCI have greater rates of contact with the health system compared with the general population. Secondary complications continue to affect persons with SCI long after the acute trauma.

The epidemiology of traumatic spinal cord injury in Alberta, Canada

OBJECTIVES To describe the incidence and pattern of traumatic spinal cord injury and cauda equina injury (SCI) in a geographically defined region of Canada. METHODS The study period was April 1, 1997 to March 31, 2000. Data were gathered from three provincial sources: administrative data from the Alberta Ministry of Health and Wellness, records from the Alberta Trauma Registry, and death certificates from the Office of the Medical Examiner. RESULTS From all three data sources, 450 cases of SCI were identified. Of these, 71 (15.8%) died prior to hospitalization. The annual incidence rate was 52.5/million population (95% CI: 47.7, 57.4). For those who survived to hospital admission, the incidence rate was 44.3/million/year (95% CI: 39.8, 48.7). The incidence rates for males were consistently higher than for females for all age groups. Motor vehicle collisions accounted for 56.4% of injuries, followed by falls (19.1%). The highest incidence of motor vehicle-related SCI occurred to those between 15 and 29 years (60/million/year). Fall-related injuries primarily occurred to those older than 60 years (45/million/year). Rural residents were 2.5 times as likely to be injured as urban residents. CONCLUSION Prevention strategies for SCI should target males of all ages, adolescents and young adults of both sexes, rural residents, motor vehicle collisions, and fall prevention for those older than 60 years.

Zones of prevention: the geography of fall injuries in the elderly

Our investigation of the geography of fall injuries considers the relationship between injury prevention and contextual approaches to health research. We use a geographic information system (GIS) to describe the pattern of emergency department reported falls of the elderly in the Capital Health Region, an administrative health area in Alberta, Canada. We used empirical Bayes estimates to obtain a geographic measure of fall incidence over the study area and a cluster detection statistic to measure the presence of a significant spatial cluster in the region. Inner-city Edmonton had the highest incidence of risk, suburban Edmonton the lowest, and surrounding rural regions and smaller communities had more moderate fall incidence. We argue that descriptive geography can enhance the effectiveness of injury prevention programs by identifying zones of high risk, even when the individual-level and contextual factors that explain the underlying patterns are unknown.

Adaptations for finding irregularly shaped disease clusters

BackgroundRecent adaptations of the spatial scan approach to detecting disease clusters have addressed the problem of finding clusters that occur in non-compact and non-circular shapes – such as along roads or river networks. Some of these approaches may have difficulty defining cluster boundaries precisely, and tend to over-fit data with very irregular (and implausible) clusters shapes.Results & DiscussionWe describe two simple adaptations to these approaches that can be used to improve the effectiveness of irregular disease cluster detection. The first adaptation penalizes very irregular cluster shapes based on a measure of connectivity (non-connectivity penalty). The second adaptation prevents searches from combining smaller clusters into large super-clusters (depth limit). We conduct experiments with simulated data in order to observe the performance of these adaptations on a number of synthetic cluster shapes.ConclusionOur results suggest that the combination of these two adaptations may increase the ability of a cluster detection method to find irregular shapes without affecting its ability to find more regular (i.e., compact) shapes. The depth limit in particular is effective when it is deemed important to distinguish nearby clusters from each other. We suggest that these adaptations of adjacency-constrained spatial scans are particularly well suited to chronic disease and injury surveillance.

Population-based study of medically treated self-inflicted injuries

OBJECTIVE Self-inflicted injury is commonly seen in emergency departments (EDs). It may be a pre-cursor to death by suicide. The objective of this study was to examine the epidemiology of self-inflicted injury presentations to EDs in the province of Alberta. METHODS Self-inflicted injury records for the 3 fiscal years 1998/99 to 2000/01 were accessed from the Ambulatory Care Classification System, a database that captures all ED encounters in the province of Alberta. Available data for each case included demographic details, location and time of visit, diagnoses and procedures. RESULTS There were 22 396 self-inflicted injury presentations to Alberta EDs during the study period. Self-inflicted injury rates were higher in females, younger patients, those on social services and those with Aboriginal treaty status. There were higher rates of return visits in the year following the self-inflicted injury than in other patient groups. Data showed regional variation. Trends could be seen in the timing of self-inflicted injury presentations by hour of day, day of week, and month of year. CONCLUSIONS Self-inflicted injury is common, with particularly high rates demonstrated among marginalized populations. This study provides comprehensive data on those who present with self-inflicted injuries, and can be used to guide further treatment, research and evaluation for this population.

Incident Cerebrovascular Disease in Rural and Urban Alberta

Study Objective: This study examines the pattern of incidence and health service utilisation of cerebrovascular disease cases in urban and rural areas within a publicly funded health care system. Design: A population-based study covering a large geographic region, using population-wide administrative health data. Age- and sex-standardised incidence and mortality rates were calculated for rural and urban areas. Final status (discharge or death), place of service and place of residence were reported for all cases across several different subsets of cerebrovascular disease. Setting: The province of Alberta, located in western Canada. Participants: Incident cases of cerebrovascular disease (stroke and transient ischaemic attack) and 4 different definitions of incident stroke were identified from data on emergency department admissions in the 1999/2000 fiscal year. Main Results: The rate of cerebrovascular disease per 10,000 was similar between urban (13.24) and rural (13.82) areas. Rural residents frequently reported their incident episode to urban emergency departments. Although the mortality is similar between urban and rural residents, rural dwellers die more frequently in the emergency department setting than urban dwellers, who die more often as in-patients. Conclusions: Overall mortality is similar between urban and rural residents. A large proportion of rural residents receive diagnoses and treatment for cerebrovascular disease in urban areas. Location of service and location of death differs between rural and urban cases of cerebrovascular disease.

Mapping commuter cycling risk in urban areas

Cycling is becoming an increasingly important transportation option for commuters. Cycling offers exercise opportunities and reduces the burden of motor vehicle travel on society. Mapping the risk of collision between cyclists and motor vehicles in urban areas is important to understanding safe cyclist route opportunities, making informed transportation planning decisions, and exploring patterns of injury epidemiology. To date, many geographic analyses and representations of cyclist risk have not taken the concept of exposure into account. Instead, risk is either expressed as a rate per capita, or as a count of events. Using data associated with the City of Hamilton, Canada, we illustrate a method for mapping commuter cyclist collision risk per distance travelled. This measure can be used to more realistically represent the underlying geography of cycling risk, and provide more geographically and empirically meaningful information to those interested in understanding how cycling safety varies over space.

An integrated framework for the geographic surveillance of chronic disease

BackgroundGeographic public health surveillance is concerned with describing and disseminating geographic information about disease and other measures of health to policy makers and the public. While methodological developments in the geographical analysis of disease are numerous, few have been integrated into a framework that also considers the effects of case ascertainment bias on the effectiveness of chronic disease surveillance.ResultsWe present a framework for the geographic surveillance of chronic disease that integrates methodological developments in the spatial statistical analysis and case ascertainment. The framework uses an hierarchical approach to organize and model health information derived from an administrative health data system, and importantly, supports the detection and analysis of case ascertainment bias in geographic data. We test the framework on asthmatic data from Alberta, Canada. We observe high prevalence in south-western Alberta, particularly among Aboriginal females. We also observe that persons likely mistaken for asthmatics tend to be distributed in a pattern similar to asthmatics, suggesting that there may be an underlying social vulnerability to a variety of respiratory illnesses, or the presence of a diagnostic practice style effect. Finally, we note that clustering of asthmatics tends to occur at small geographic scales, while clustering of persons mistaken for asthmatics tends to occur at larger geographic scales.ConclusionRoutine and ongoing geographic surveillance of chronic diseases is critical to developing an understanding of underlying epidemiology, and is critical to informing policy makers and the public about the health of the population.

West nile virus : Strategies for predicting municipal-level infection

Abstract:  The appearance and spread of West Nile virus (WNv) in North America represent a recent example of how mosquito‐borne diseases can develop in new settings. Understanding the epidemiological, biological, and geographical aspects of WNv is critical to developing a greater understanding of how newly emerging, migrating, or evolving vector‐borne infectious disease can develop globally. To aid in the allocation of resources that mitigate future outbreaks and to better understand the geographic nature of WNv in the North American prairies, we employ spatial and nonspatial modeling methods to predict municipal‐level risk of human WNv infection rates. We use data based on a combination of routinely collected electronic data sources. Our findings suggest general agreement between spatial and nonspatial approaches, and results are consistent with seroprevalence‐based estimates. We suggest that spatial models based on administrative data can offer estimates of relative risk in human populations at less cost, and in a timelier manner than estimates based on serology specimens.