A population health perspective on artificial intelligence.

The burgeoning field of Artificial Intelligence (AI) has the potential to profoundly impact the public's health. Yet, to make the most of this opportunity, decision-makers must understand AI concepts. In this article, we describe approaches and fields within AI and illustrate through examples how they can contribute to informed decisions, with a focus on population health applications. We first introduce core concepts needed to understand modern uses of AI and then describe its sub-fields. Finally, we examine four sub-fields of AI most relevant to population health along with examples of available tools and frameworks. Artificial intelligence is a broad and complex field, but the tools that enable the use of AI techniques are becoming more accessible, less expensive, and easier to use than ever before. Applications of AI have the potential to assist clinicians, health system managers, policy-makers, and public health practitioners in making more precise, and potentially more effective, decisions.

International travel between global urban centres vulnerable to yellow fever transmission.

OBJECTIVE: To examine the potential for international travel to spread yellow fever virus to cities around the world. METHODS: We obtained data on the international flight itineraries of travellers who departed yellow fever-endemic areas of the world in 2016 for cities either where yellow fever was endemic or which were suitable for viral transmission. Using a global ecological model of dengue virus transmission, we predicted the suitability of cities in non-endemic areas for yellow fever transmission. We obtained information on national entry requirements for yellow fever vaccination at travellers' destination cities. FINDINGS: In 2016, 45.2 million international air travellers departed from yellow fever-endemic areas of the world. Of 11.7 million travellers with destinations in 472 cities where yellow fever was not endemic but which were suitable for virus transmission, 7.7 million (65.7%) were not required to provide proof of vaccination upon arrival. Brazil, China, India, Mexico, Peru and the United States of America had the highest volumes of travellers arriving from yellow fever-endemic areas and the largest populations living in cities suitable for yellow fever transmission. CONCLUSION: Each year millions of travellers depart from yellow fever-endemic areas of the world for cities in non-endemic areas that appear suitable for viral transmission without having to provide proof of vaccination. Rapid global changes in human mobility and urbanization make it vital for countries to re-examine their vaccination policies and practices to prevent urban yellow fever epidemics.

Priority-setting in public health research funding organisations: an exploratory qualitative study among five high-profile funders.

BACKGROUND: Priority-driven funding streams for population and public health are an important part of the health research landscape and contribute to orienting future scholarship in the field. While research priorities are often made public through targeted calls for research, less is known about how research funding organisations arrive at said priorities. Our objective was to explore how public health research funding organisations develop priorities for strategic extramural research funding programmes. METHODS: Content analysis of published academic and grey literature and key informant interviews for five public and private funders of public health research in the United Kingdom, Australia, the United States and France were performed. RESULTS: We found important distinctions in how funding organisations processed potential research priorities through four non-sequential phases, namely idea generation, idea analysis, idea socialisation and idea selection. Funders generally involved the public health research community and public health decision-makers in idea generation and socialisation, but other groups of stakeholders (e.g. the public, advocacy organisations) were not as frequently included. CONCLUSIONS: Priority-setting for strategic funding programmes in public health research involves consultation mainly with researchers in the early phase of the process. There is an opportunity for greater breadth of participation and more transparency in priority-setting mechanisms for strategic funding programmes in population and public health research.

A Population-Based Cross-Sectional Study Comparing Breast Cancer Stage at Diagnosis between Immigrant and Canadian-Born Women in Ontario.

There is limited information on stage at breast cancer diagnosis in Canadian immigrant women. We compared stage at diagnosis between immigrant women and Canadian-born women, and determined whether ethnicity was an independent factor associated with stage. 41,213 women with invasive breast cancer from 2007 to 2012 were identified from the Ontario Cancer Registry. Women were classified as either immigrants or Canadian-born by linkage with the Immigration, Refugees, and Citizenship Canada's Permanent Resident database. Women's ethnicity was classified as Chinese, South Asian, or remaining women in Ontario. Logistic regression was performed to calculate the odds ratio (OR) of being diagnosed at stage I breast cancer (versus stage II-IV). 4,353 (10.6%) women were immigrants and 36,860 (89.4%) were Canadian-born women. The mean age at breast cancer diagnosis was 53.5 years for immigrants versus 62.3 years for Canadian-born women (p < 0.0001). Immigrant women were less likely than Canadian-born women to be diagnosed with stage I breast cancers (adjusted OR = 0.85; 95% CI: 0.79-0.91; p < 0.0001). The adjusted OR of being stage I was 1.28 (95% CI: 1.14-1.43; p < 0.0001) for women of Chinese ethnicity and was 0.82 (95% CI: 0.70-0.96; p = 0.01) for women of South Asian ethnicity, compared to the remaining women in Ontario. Canadian immigrant women were less likely than Canadian-born women to be diagnosed with early-stage breast cancers. Ethnicity was a greater contributor to the stage disparity than was immigrant status. South Asian women, regardless of immigration status, might benefit from increased breast cancer awareness programs.

Identifying mechanisms for facilitating knowledge to action strategies targeting the built environment.

BACKGROUND: In recent years, obesity-related diseases have been on the rise globally resulting in major challenges for health systems and society as a whole. Emerging research in population health suggests that interventions targeting the built environment may help reduce the burden of obesity and type 2 diabetes. However, translation of the evidence on the built environment into effective policy and planning changes requires engagement and collaboration between multiple sectors and government agencies for designing neighborhoods that are more conducive to healthy and active living. In this study, we identified knowledge gaps and other barriers to evidence-based decision-making and policy development related to the built environment; as well as the infrastructure, processes, and mechanisms needed to drive policy changes in this area. METHODS: We conducted a qualitative thematic analysis of data collected through consultations with a broad group of stakeholders (N = 42) from Southern Ontario, Canada, within various sectors (public health, urban planning, and transportation) and levels of government (federal, provincial, and municipalities). Relevant themes were classified based on the specific phase of the knowledge-to-action cycle (research, translation, and implementation) in which they were most closely aligned. RESULTS: We identified 5 themes including: 1) the need for policy-informed and actionable research (e.g. health economic analyses and policy evaluations); 2) impactful messaging that targets all relevant sectors to create the political will necessary to drive policy change; 3) common measures and tools to increase capacity for monitoring and surveillance of built environment changes; (4) intersectoral collaboration and alignment within and between levels of government to enable collective actions and provide mechanisms for sharing of resources and expertise, (5) aligning public and private sector priorities to generate public demand and support for community action; and, (6) solution-focused implementation of research that will be tailored to meet the needs of policymakers and planners. Additional research priorities and key policy and planning actions were also noted. CONCLUSION: Our research highlights the necessity of involving stakeholders in identifying inter-sectoral solutions to develop and translate actionable research on the built environment into effective policy and planning initiatives.

Assessment of the potential for international dissemination of Ebola virus via commercial air travel during the 2014 west African outbreak.

BACKGROUND: The WHO declared the 2014 west African Ebola epidemic a public health emergency of international concern in view of its potential for further international spread. Decision makers worldwide are in need of empirical data to inform and implement emergency response measures. Our aim was to assess the potential for Ebola virus to spread across international borders via commercial air travel and assess the relative efficiency of exit versus entry screening of travellers at commercial airports. METHODS: We analysed International Air Transport Association data for worldwide flight schedules between Sept 1, 2014, and Dec 31, 2014, and historic traveller flight itinerary data from 2013 to describe expected global population movements via commercial air travel out of Guinea, Liberia, and Sierra Leone. Coupled with Ebola virus surveillance data, we modelled the expected number of internationally exported Ebola virus infections, the potential effect of air travel restrictions, and the efficiency of airport-based traveller screening at international ports of entry and exit. We deemed individuals initiating travel from any domestic or international airport within these three countries to have possible exposure to Ebola virus. We deemed all other travellers to have no significant risk of exposure to Ebola virus. FINDINGS: Based on epidemic conditions and international flight restrictions to and from Guinea, Liberia, and Sierra Leone as of Sept 1, 2014 (reductions in passenger seats by 51% for Liberia, 66% for Guinea, and 85% for Sierra Leone), our model projects 2.8 travellers infected with Ebola virus departing the above three countries via commercial flights, on average, every month. 91,547 (64%) of all air travellers departing Guinea, Liberia, and Sierra Leone had expected destinations in low-income and lower-middle-income countries. Screening international travellers departing three airports would enable health assessments of all travellers at highest risk of exposure to Ebola virus infection. INTERPRETATION: Decision makers must carefully balance the potential harms from travel restrictions imposed on countries that have Ebola virus activity against any potential reductions in risk from Ebola virus importations. Exit screening of travellers at airports in Guinea, Liberia, and Sierra Leone would be the most efficient frontier at which to assess the health status of travellers at risk of Ebola virus exposure, however, this intervention might require international support to implement effectively. FUNDING: Canadian Institutes of Health Research.

Preterm Delivery in Relation to Neighbourhood-Level Adult Premature Mortality.

OBJECTIVE: To assess the influence of neighbourhood-level adult premature mortality on a woman's risk of preterm delivery (PTD). METHODS: We included 286 872 singleton live birth deliveries in Toronto, Ontario, between 2002 and 2011. The study exposure was neighbourhood premature mortality rate, expressed in quintiles (Q), among adults aged 20 to 49 years living within each of Toronto's 140 neighbourhoods. The primary study outcome was PTD at 24 to 36 weeks' gestation. Logistic regression analysis generated unadjusted ORs, adjusted ORs, and 95% CIs, controlling for maternal age, parity, marital status, material deprivation index Q, maternal and paternal birthplace, and infant sex. RESULTS: For all 140 neighbourhoods, the mean rate of premature deaths was 0.66 per 100 females and 1.17 per 100 males aged 20 to 49 years. The rate of PTD increased linearly in relation to the neighbourhood rate of premature mortality among adult females, from 5.3 per 100 in Q1 with the lowest rate of premature mortality to 6.3 per 100 in Q5 (OR 1.22; 95% CI 1.13 to 1.31). The adjusted ORs were attenuated but remained significant (1.13; 95% CI 1.05 to 1.22). A similar pattern was demonstrated for the relation between neighbourhood premature mortality among adult males and PTD. CONCLUSION: Women residing in neighbourhoods with high rates of premature adult mortality are at elevated risk of PTD, even after adjusting for measured socioeconomic factors that include marital status and material deprivation.

Association of Neighborhood Walkability With Change in Overweight, Obesity, and Diabetes.

IMPORTANCE: Rates of obesity and diabetes have increased substantially in recent decades; however, the potential role of the built environment in mitigating these trends is unclear. OBJECTIVE: To examine whether walkable urban neighborhoods are associated with a slower increase in overweight, obesity, and diabetes than less walkable ones. DESIGN, SETTING, AND PARTICIPANTS: Time-series analysis (2001-2012) using annual provincial health care (N ≈ 3 million per year) and biennial Canadian Community Health Survey (N ≈ 5500 per cycle) data for adults (30-64 years) living in Southern Ontario cities. EXPOSURES: Neighborhood walkability derived from a validated index, with standardized scores ranging from 0 to 100, with higher scores indicating more walkability. Neighborhoods were ranked and classified into quintiles from lowest (quintile 1) to highest (quintile 5) walkability. MAIN OUTCOMES AND MEASURES: Annual prevalence of overweight, obesity, and diabetes incidence, adjusted for age, sex, area income, and ethnicity. RESULTS: Among the 8777 neighborhoods included in this study, the median walkability index was 16.8, ranging from 10.1 in quintile 1 to 35.2 in quintile 5. Resident characteristics were generally similar across neighborhoods; however, poverty rates were higher in high- vs low-walkability areas. In 2001, the adjusted prevalence of overweight and obesity was lower in quintile 5 vs quintile 1 (43.3% vs 53.5%; P < .001). Between 2001 and 2012, the prevalence increased in less walkable neighborhoods (absolute change, 5.4% [95% CI, 2.1%-8.8%] in quintile 1, 6.7% [95% CI, 2.3%-11.1%] in quintile 2, and 9.2% [95% CI, 6.2%-12.1%] in quintile 3). The prevalence of overweight and obesity did not significantly change in areas of higher walkability (2.8% [95% CI, -1.4% to 7.0%] in quintile 4 and 2.1% [95% CI, -1.4% to 5.5%] in quintile 5). In 2001, the adjusted diabetes incidence was lower in quintile 5 than other quintiles and declined by 2012 from 7.7 to 6.2 per 1000 persons in quintile 5 (absolute change, -1.5 [95% CI, -2.6 to -0.4]) and 8.7 to 7.6 in quintile 4 (absolute change, -1.1 [95% CI, -2.2 to -0.05]). In contrast, diabetes incidence did not change significantly in less walkable areas (change, -0.65 in quintile 1 [95% CI, -1.65 to 0.39], -0.5 in quintile 2 [95% CI, -1.5 to 0.5], and -0.9 in quintile 3 [95% CI, -1.9 to 0.02]). Rates of walking or cycling and public transit use were significantly higher and that of car use lower in quintile 5 vs quintile 1 at each time point, although daily walking and cycling frequencies increased only modestly from 2001 to 2011 in highly walkable areas. Leisure-time physical activity, diet, and smoking patterns did not vary by walkability (P > .05 for quintile 1 vs quintile 5 for each outcome) and were relatively stable over time. CONCLUSIONS AND RELEVANCE: In Ontario, Canada, higher neighborhood walkability was associated with decreased prevalence of overweight and obesity and decreased incidence of diabetes between 2001 and 2012. However, the ecologic nature of these findings and the lack of evidence that more walkable urban neighborhood design was associated with increased physical activity suggest that further research is necessary to assess whether the observed associations are causal.

Domestic impact of tuberculosis screening among new immigrants to Ontario, Canada.

BACKGROUND: All Canadian immigrants undergo screening for tuberculosis (TB) before immigration, and selected immigrants must undergo postimmigration surveillance for the disease. We sought to quantify the domestic health impact of screening for TB in all new immigrants and to identify mechanisms to enhance effectiveness and efficiency of this screening. METHODS: We linked preimmigration medical examination records from 944,375 immigrants who settled in Ontario between 2002 and 2011 to active TB reporting data in Ontario between 2002 and 2011. Using a retrospective cohort study design, we measured birth country-specific rates of active TB detected through preimmigration screening and postimmigration surveillance. We then quantified the proportion of active TB cases among residents of Ontario born abroad that were detected through postimmigration surveillance. Using Cox regression, we identified independent predictors of active TB postimmigration. RESULTS: Immigrants from 6 countries accounted for 87.3% of active TB cases detected through preimmigration screening, and 10 countries accounted for 80.4% of cases detected through postimmigration surveillance. Immigrants from countries with a TB (all-sites) incidence rate of less than 30 cases per 100 000 persons resulted in pre- and postimmigration detection of 2.4 and 0.9 cases per 100 000 immigrants, respectively. Postimmigration surveillance detected 2.6% of active TB cases in Ontario residents born abroad, and TB was detected a median of 18 days earlier in those undergoing surveillance than in those who were not referred to surveillance or who did not comply. Predictors of active TB postimmigration included radiographic markers of old TB, birth country, immigration category, location of application for residency, immune status and age. INTERPRETATION: Universal screening for TB in new immigrants has a modest impact on the domestic burden of active TB and is highly inefficient. Focusing preimmigration screening in countries with high incidence rates and revising criteria for postimmigration surveillance could increase the effectiveness and efficiency of screening.

A Population-Based Study of Diabetes Incidence by Ethnicity and Age: Support for the Development of Ethnic-Specific Prevention Strategies.

OBJECTIVE: Although national guidelines advocate for earlier diabetes screening in high-risk ethnic groups, little evidence exists to guide clinicians on the age at which screening should commence. The purpose of this study was to determine age equivalency thresholds for diabetes risk across a broad range of ethnic populations. METHODS: This population-based, retrospective cohort study used linked administrative health and immigration records for 592,376 individuals in Ontario, Canada. Adjusted incidence rates by ethnicity, sex and age were used to derive ethnic-specific age thresholds for risk. RESULTS: Diabetes incidence rates in South Asians reached an equivalent risk as that experienced by a 40-year-old Western European man (3.7 per 1,000 person-years) by 25 years of age. For all other non-European ethnic groups, the equivalent risk was experienced between 30 and 35 years of age. These risk differentials persisted despite controlling for covariates. CONCLUSIONS: We found a 15-year difference in age equivalency of risk across ethnic groups.

Correction to: Why public health matters today and tomorrow: the role of applied public health research.

The article "Why public health matters today and tomorrow: the role of applied public health research," written by Lindsay McLaren et al., was originally published Online First without Open Access.

Building the political case for investing in public health and public health research.

Governments around the world vastly underinvest in public health, despite ever growing evidence demonstrating its economic and social benefits. Challenges in securing greater public health investment largely stem from the necessity for governments to demonstrate visible impacts within an election cycle, whereas public health initiatives operate over the long term and generally involve prevention, statistical lives and underlying conditions. It is time for the public health community to rethink its strategies and craft political wins by building a political case for investing in public health-which extends far beyond mere economic and social arguments. These strategies need to make public health visible, account for the complexities of policymaking networks and adapt knowledge translation efforts to the appropriate policy instrument.

Neighbourhood walkability and the incidence of diabetes: an inverse probability of treatment weighting analysis.

BACKGROUND: People living in highly walkable neighbourhoods tend to be more physically active and less likely to be obese. Whether walkable urban design reduces the future risk of diabetes is less clear. METHODS: We used inverse probability of treatment weighting to compare 10-year diabetes incidence between residents living in high-walkability and low-walkability neighbourhoods within five urban regions in Ontario, Canada. Adults (aged 30-85 years) who were diabetes-free on 1 April 2002 were identified from administrative health databases and followed until 31 March 2012 (n=958 567). Within each region, weights reflecting the propensity to live in each neighbourhood type were created based on sociodemographic characteristics, comorbidities and healthcare utilisation and incorporated into region-specific Cox proportional hazards models. RESULTS: Low-walkability areas were more affluent and had more South Asian residents (6.4%vs3.6%, p<0.001) but fewer residents from other minority groups (16.6%vs21.7%, p<0.001). Baseline characteristics were well balanced between low-walkability and high-walkability neighbourhoods after applying individual weights (standardised differences all <0.1). In each region, high walkability was associated with lower diabetes incidence among adults aged <65 years (overall weighted incidence: 8.2vs9.2 per 1000; HR 0.85, 95% CI 0.78 to 0.93), but not among adults aged ≥65 years (weighted incidence: 20.7vs19.5 per 1000; HR 1.01, 95% CI 0.91 to 1.12). Findings were consistent regardless of income and immigration status. CONCLUSIONS: Younger adults living in high-walkability neighbourhoods had a lower 10-year incidence of diabetes than similarly aged adults living in low-walkability neighbourhoods. Urban designs that support walking may have important benefits for diabetes prevention.

Why public health matters today and tomorrow: the role of applied public health research.

Public health is critical to a healthy, fair, and sustainable society. Realizing this vision requires imagining a public health community that can maintain its foundational core while adapting and responding to contemporary imperatives such as entrenched inequities and ecological degradation. In this commentary, we reflect on what tomorrow's public health might look like, from the point of view of our collective experiences as researchers in Canada who are part of an Applied Public Health Chairs program designed to support "innovative population health research that improves health equity for citizens in Canada and around the world." We view applied public health research as sitting at the intersection of core principles for population and public health: namely sustainability, equity, and effectiveness. We further identify three attributes of a robust applied public health research community that we argue are necessary to permit contribution to those principles: researcher autonomy, sustained intersectoral research capacity, and a critical perspective on the research-practice-policy interface. Our intention is to catalyze further discussion and debate about why and how public health matters today and tomorrow, and the role of applied public health research therein.

Elevation as a proxy for mosquito-borne Zika virus transmission in the Americas.

INTRODUCTION: When Zika virus (ZIKV) first began its spread from Brazil to other parts of the Americas, national-level travel notices were issued, carrying with them significant economic consequences to affected countries. Although regions of some affected countries were likely unsuitable for mosquito-borne transmission of ZIKV, the absence of high quality, timely surveillance data made it difficult to confidently demarcate infection risk at a sub-national level. In the absence of reliable data on ZIKV activity, a pragmatic approach was needed to identify subnational geographic areas where the risk of ZIKV infection via mosquitoes was expected to be negligible. To address this urgent need, we evaluated elevation as a proxy for mosquito-borne ZIKV transmission. METHODS: For sixteen countries with local ZIKV transmission in the Americas, we analyzed (i) modelled occurrence of the primary vector for ZIKV, Aedes aegypti, (ii) human population counts, and (iii) reported historical dengue cases, specifically across 100-meter elevation levels between 1,500m and 2,500m. Specifically, we quantified land area, population size, and the number of observed dengue cases above each elevation level to identify a threshold where the predicted risks of encountering Ae. aegypti become negligible. RESULTS: Above 1,600m, less than 1% of each country's total land area was predicted to have Ae. aegypti occurrence. Above 1,900m, less than 1% of each country's resident population lived in areas where Ae. aegypti was predicted to occur. Across all 16 countries, 1.1% of historical dengue cases were reported above 2,000m. DISCUSSION: These results suggest low potential for mosquito-borne ZIKV transmission above 2,000m in the Americas. Although elevation is a crude predictor of environmental suitability for ZIKV transmission, its constancy made it a pragmatic input for policy decision-making during this public health emergency.

Potential for Zika virus introduction and transmission in resource-limited countries in Africa and the Asia-Pacific region: a modelling study.

BACKGROUND: As the epidemic of Zika virus expands in the Americas, countries across Africa and the Asia-Pacific region are becoming increasingly susceptible to the importation and possible local spread of the virus. To support public health readiness, we aim to identify regions and times where the potential health, economic, and social effects from Zika virus are greatest, focusing on resource-limited countries in Africa and the Asia-Pacific region. METHODS: Our model combined transportation network analysis, ecological modelling of mosquito occurrences, and vector competence for flavivirus transmission, using data from the International Air Transport Association, entomological observations from Zika's primary vector species, and climate conditions using WorldClim. We overlaid monthly flows of airline travellers arriving to Africa and the Asia-Pacific region from areas of the Americas suitable for year-round transmission of Zika virus with monthly maps of climatic suitability for mosquito-borne transmission of Zika virus within Africa and the Asia-Pacific region. FINDINGS: An estimated 2·6 billion people live in areas of Africa and the Asia-Pacific region where the presence of competent mosquito vectors and suitable climatic conditions could support local transmission of Zika virus. Countries with large volumes of travellers arriving from Zika virus-affected areas of the Americas and large populations at risk of mosquito-borne Zika virus infection include India (67 422 travellers arriving per year; 1·2 billion residents in potential Zika transmission areas), China (238 415 travellers; 242 million residents), Indonesia (13 865 travellers; 197 million residents), Philippines (35 635 travellers; 70 million residents), and Thailand (29 241 travellers; 59 million residents). INTERPRETATION: Many countries across Africa and the Asia-Pacific region are vulnerable to Zika virus. Strategic use of available health and human resources is essential to prevent or mitigate the health, economic, and social consequences of Zika virus, especially in resource-limited countries. FUNDING: Canadian Institutes of Health Research and the US Centers for Disease Control and Prevention.

Age- and sex-specific income gradients in alcohol-related hospitalization rates in an urban area.

PURPOSE: This study examines the effects of age and sex on the relationship between neighborhood income and alcohol-related hospitalization rates in a large urban area. METHODS: Adults in Toronto, Canada, who were hospitalized with an alcohol-related condition between 1995 and 1998 were identified using discharge diagnoses. Income quintiles were determined based on area of residence. Annual rates of hospitalization for alcohol-related conditions per 10,000 individuals were calculated. RESULTS: Rates of hospitalization with a primary diagnosis of an alcohol-related condition were similar among men age 20 to 39 in all incomes quintiles, but were inversely associated with income among men age 40 to 64 (28.8 and 13.3 per 10,000 in the lowest and highest income quintiles). Among women age 40 to 64, the lowest income quintile had the highest hospitalization rate (12.1 per 10,000), but women in all other income quintiles had relatively low hospitalization rates (5.9 to 7.7 per 10,000). As age increased above 65 years, rates of hospitalization with a primary diagnosis of an alcohol-related condition decreased or stabilized in both men and women. CONCLUSIONS: The inverse association between income level and alcohol-related hospitalization rates becomes apparent after age 40. A gradient in hospitalization rates is seen in men across all income levels, but in women a prominent effect is seen only in those with the lowest income.

Assessment of police calls for suicidal behavior in a concentrated urban setting.

As a result of deinstitutionalization over the past half-century, police have become frontline mental health care workers. This study assessed five-year patterns of police calls for suicidal behavior in Toronto, Canada. Police responded to an average of 1,422 calls for suicidal behavior per year, 15 percent of which involved completed suicides (24 percent of male callers and 8 percent of female callers). Calls for suicidal behavior increased by 4 percent among males and 17 percent among females over the study period. The rate of completed suicides decreased by 22 percent among males and 31 percent among females. Compared with women, men were more likely to die from physical (as opposed to chemical) methods (22 percent and 43 percent, respectively). The study results highlight the importance of understanding changes in patterns and types of suicidal behavior to police training and preparedness.

Socioeconomic misclassification in Ontario's Health Care Registry.

BACKGROUND: Addresses in some provincial health care registries are not systematically updated. If individuals are attributed to the wrong location, this can lead to errors in health care planning and research. Our purpose was to investigate the accuracy of socioeconomic classification based on addresses in Ontario's provincial health care registry. METHODS: The study setting was Toronto's inner city, an area with a population of 799,595 in 1996. We ordered enumeration areas by 1996 mean household income and divided them into five roughly equal income groups by population. We then assigned an income quintile to each individual using both the address from Ontario's provincial heath care registry and that from hospital discharge abstracts. We compared these two sets of income quintiles and also used them to generate quintile-specific rates of medical hospital admissions in the year 2000. RESULTS: Provincial registry and hospital-based addresses agreed on the exact enumeration area for 78.1% of individuals and for income quintile for 84.8% of individuals. Disagreement by more than one income quintile occurred for 7.4% of individuals. The two methods of assigning income quintiles yielded income-specific medical hospitalization rates and rate ratios that agreed within 1%. INTERPRETATION: Although address inaccuracy was found in Ontario's health care registry, serious socioeconomic misclassification occurred at a relatively low rate and did not appear to introduce significant bias in the calculation of hospital rates by socioeconomic group. Updating of addresses at regular intervals is highly desirable and would result in improved accuracy of provincial health care registries.

Neighbourhood recent immigration and hospitalization in Toronto, Canada.

Recent immigrants to Canada tend to initially settle in low-income urban core areas. The relationships among immigration, neighbourhood effects and health are poorly understood. This study explored the risk of hospitalization in high recent-immigration areas in Toronto compared to other Toronto neighbourhoods. The study used 1996 hospitalization and census data. Regression was used to examine the effects of recent immigration on neighbourhood hospitalization rates. Most hospitalization categories showed significantly higher rates of admission as the proportion of recent immigrants increased. Income was also significantly associated with all categories of hospitalization except surgical admissions. Average household income was almost 60% lower (dollar 36,122) in the highest versus the lowest immigration areas (dollar 82,641) suggesting that, at the neighbourhood level, the effects of immigration and income may be difficult to disentangle. These findings have important implications for health care planning, delivery, and policy.