Maria Chiu

Deriving Ethnic-Specific BMI Cutoff Points for Assessing Diabetes Risk

OBJECTIVE The definition of obesity (BMI ≥30 kg/m2), a key risk factor of diabetes, is widely used in white populations; however, its appropriateness in nonwhite populations has been questioned. We compared the incidence rates of diabetes across white, South Asian, Chinese, and black populations and identified equivalent ethnic-specific BMI cutoff values for assessing diabetes risk. RESEARCH DESIGN AND METHODS We conducted a multiethnic cohort study of 59,824 nondiabetic adults aged ≥30 years living in Ontario, Canada. Subjects were identified from Statistics Canada’s population health surveys and followed for up to 12.8 years for diabetes incidence using record linkages to multiple health administrative databases. RESULTS The median duration of follow-up was 6 years. After adjusting for age, sex, sociodemographic characteristics, and BMI, the risk of diabetes was significantly higher among South Asian (hazard ratio 3.40, P < 0.001), black (1.99, P < 0.001), and Chinese (1.87, P = 0.002) subjects than among white subjects. The median age at diagnosis was lowest among South Asian (aged 49 years) subjects, followed by Chinese (aged 55 years), black (aged 57 years), and white (aged 58 years) subjects. For the equivalent incidence rate of diabetes at a BMI of 30 kg/m2 in white subjects, the BMI cutoff value was 24 kg/m2 in South Asian, 25 kg/m2 in Chinese, and 26 kg/m2 in black subjects. CONCLUSIONS South Asian, Chinese, and black subjects developed diabetes at a higher rate, at an earlier age, and at lower ranges of BMI than their white counterparts. Our findings highlight the need for designing ethnically tailored prevention strategies and for lowering current targets for ideal body weight for nonwhite populations.

Trends in risk factors for cardiovascular disease in Canada: temporal, socio-demographic and geographic factors

Background: Temporal trends in risk factors for cardiovascular disease and the impact of socio-economic status on these risk factors remain unclear. Methods: Using data from the National Population Health Survey and the Canadian Community Health Survey, we examined national trends in heart disease, hypertension, diabetes mellitus, obesity and smoking prevalence from 1994 to 2005, adjusting for age and sex. We stratified data by income adequacy category, body mass index and region of residence. Results: An estimated 1.29 million Canadians reported having heart disease in 2005, representing increases of 19% for men and 2% for women, relative to 1994. Heart disease increased significantly in the lowest income category (by 27%), in the lower middle income category (by 37%) and in the upper middle income category (by 12%); however, it increased by only 6% in the highest income group. Diabetes increased in all but the highest income group: by 56% in the lowest income group, by 93% in the lower middle income group and by 59% in the upper middle income group. Hypertension increased in all income groups: by 85% in the lowest income group, by 80% in the lower middle income group, by 91% in the upper middle income group and by 117% in the highest income group. Obesity also increased in all income groups: by 20% in the lowest income group, by 25% in the lower middle income group, by 33% in the upper middle income group and by 37% in the highest income group. In addition to socio-economic status, obesity and overweight also modified the trends in risk factors. Diabetes increased to a greater extent among obese participants (61% increase) and overweight participants (25% increase), as did hypertension, which increased by 80% among obese individuals and by 74% among overweight individuals. Trends in diabetes, hypertension and obesity were consistent for all provinces. Interpretation: During the study period, heart disease, hypertension, diabetes and obesity increased for all or most income groups in Canada. Further interventions supporting modification of lifestyle and risk factors are needed to prevent future cardiovascular disease.

Comparison of cardiovascular risk profiles among ethnic groups using population health surveys between 1996 and 2007

Background: Although people of South Asian, Chinese and black ethnic backgrounds represent about 60% of the world’s population, most knowledge of cardiovascular risk is derived from studies conducted in white populations. We conducted a large, population-based comparison of cardiovascular risk among people of white, South Asian, Chinese and black ethnicity living in Ontario, Canada. Methods: We examined the age- and sex-standardized prevalence of eight cardiovascular risk factors, heart disease and stroke among 154 653 white people, 3364 South Asian people, 3038 Chinese people and 2742 black people. For this study, we pooled respondent data from five cross-sectional health surveys conducted between 1996 and 2007: the National Population Health Survey of 1996 and the Canadian Community Health Survey, versions 1.1, 2.1, 3.1 and 4.1. Results: The four ethnic groups varied considerably in the prevalence of the four major cardiovascular risk factors that we examined: for smoking, South Asian 8.6%, Chinese 8.7%, black 11.4% and white 24.8%; for obesity, Chinese 2.5%, South Asian 8.1%, black 14.1% and white 14.8%; for diabetes mellitus, white 4.2%, Chinese 4.3%, South Asian 8.1% and black 8.5%; and for hypertension, white 13.7%, Chinese 15.1%, South Asian 17.0% and black 19.8%. The prevalence of heart disease ranged from a low of 3.2% in the Chinese population to a high of 5.2% in the South Asian population, and the prevalence of stroke ranged from a low of 0.6% in the Chinese population to a high of 1.7% in the South Asian population. Although the black population had the least favourable cardiovascular risk factor profile overall, this group had a relatively low prevalence of heart disease (3.4%). Interpretation: Ethnic groups living in Ontario had striking differences in cardiovascular risk profiles. Awareness of these differences may help in identifying priorities for the development of cardiovascular disease prevention programs for specific ethnic groups.

Surname lists to identify South Asian and Chinese ethnicity from secondary data in Ontario, Canada: a validation study

BackgroundSurname lists are useful for identifying cohorts of ethnic minority patients from secondary data sources. This study sought to develop and validate lists to identify people of South Asian and Chinese origin.MethodsComprehensive lists of South Asian and Chinese surnames were reviewed to identify those that uniquely belonged to the ethnic minority group. Surnames that were common in other populations, communities or ethnic groups were specifically excluded. These surname lists were applied to the Registered Persons Database, a registry of the health card numbers assigned to all residents of the Canadian province of Ontario, so that all residents were assigned to South Asian ethnicity, Chinese ethnicity or the General Population. Ethnic assignment was validated against self-identified ethnicity through linkage with responses to the Canadian Community Health Survey.ResultsThe final surname lists included 9,950 South Asian surnames and 1,133 Chinese surnames. All 16,688,384 current and former residents of Ontario were assigned to South Asian ethnicity, Chinese ethnicity or the General Population based on their surnames. Among 69,859 respondents to the Canadian Community Health Survey, both lists performed extremely well when compared against self-identified ethnicity: positive predictive value was 89.3% for the South Asian list, and 91.9% for the Chinese list. Because surnames shared with other ethnic groups were deliberately excluded from the lists, sensitivity was lower (50.4% and 80.2%, respectively).ConclusionsThese surname lists can be used to identify cohorts of people with South Asian and Chinese origins from secondary data sources with a high degree of accuracy. These cohorts could then be used in epidemiologic and health service research studies of populations with South Asian and Chinese origins.

Cardiovascular Risk Factor Profiles of Recent Immigrants vs Long-term Residents of Ontario: A Multi-ethnic Study

BACKGROUND There is growing evidence that cardiovascular risk profiles differ markedly across Canadas 4 major ethnic groups, namely White, South Asian, Chinese, and Black; however, the impact of long-term Canadian residency on cardiovascular risk within and across these ethnic groups is unknown. METHODS Using pooled data from Statistics Canadas National Population and Canadian Community Health Surveys (1996-2007), we compared the age- and sex-standardized prevalence of cardiovascular risk factors and diseases between recent immigrants (< 15 years in Canada) and long-term residents (immigrants who lived in Canada for ≥ 15 years or people born in Canada) among White, South Asian, Chinese, and Black ethnic groups living in Ontario. We also calculated ethnic-specific attributable fraction (AF), defined as the proportion of risk that can be attributed to long-term Canadian residency. RESULTS For all ethnic groups, cardiovascular risk factor profiles (ie, the percentage of people with ≥ 2 major cardiovascular risk factors, ie, smoking, obesity, diabetes, and hypertension) were worse among those with longer duration of residency in Canada. The greatest change in recent immigrants vs long-term residents was observed in the Chinese group (2.2% vs 5.2%; AF 0.47) followed by the White (6.5% vs 10.3%; AF 0.36), Black (9.2% vs 12.1%; AF 0.17), and South Asian (7.7% vs 8.2%; AF 0.03) groups. The prevalence of cardiovascular disease did not differ significantly between recent immigrants and long-term residents, irrespective of ethnic group. CONCLUSIONS Our results suggest that cardiovascular disease prevention strategies must consider not only ethnicity, but also the level of acculturation within each ethnic group.

Safety and Effectiveness of Drug-Eluting and Bare-Metal Stents for Patients With Off- and On-Label Indications

OBJECTIVES Our main objective was to evaluate the longer-term safety and efficacy of drug-eluting stents (DES) in off-label indications as compared with bare-metal stents (BMS). BACKGROUND DES are frequently implanted in patients with off-label indications. However, the longer-term safety and effectiveness of DES among patients with off-label indications are not well understood. METHODS Propensity score matching analysis was performed in a population-based cohort that included 6,944 off-label and 9,126 on-label patients who received percutaneous coronary interventions (PCIs) in Ontario, Canada, between December 1, 2003, and March 31, 2006. Off-label indications were defined on the basis of clinical and procedural characteristics. RESULTS For patients with off-label indications, rates of repeat target vessel revascularization at 3 years were significantly lower among patients treated with DES compared with those treated with BMS (11.6% vs. 15.3%, p < 0.001). Myocardial infarction rates were not significantly different between patients treated with DES and BMS (p = 0.52). Mortality rates were significantly lower among off-label patients treated with DES compared with BMS at 3 years of follow-up (6.9% vs. 10.5%, p < 0.001). For patients with on-label indications, the use of DES was associated with significantly lower rates of target vessel revascularization, but composite rates of myocardial infarction or death were not significantly different from BMS. CONCLUSIONS For patients with off-label indications, DES implantation was associated with lower target vessel revascularization without an associated increase in longer-term risk of myocardial infarction or death compared with BMS.

Effect of marriage on duration of chest pain associated with acute myocardial infarction before seeking care

Background: Coronary artery disease is the most common cause of death in the Western world, and being married decreases the risk of death from cardiovascular causes. We aimed to determine whether marital status was a predictor of the duration of chest pain endured by patients with acute myocardial infarction before they sought care and whether the patient’s sex modified the effect. Methods: We conducted a retrospective, population-based cohort analysis of patients with acute myocardial infarction admitted to 96 acute care hospitals in Ontario, Canada, from April 2004 to March 2005. We excluded patients who did not experience chest pain. Using multivariable regression analyses, we assessed marital status in relation to delayed presentation to hospital (more than six hours from onset of pain), both overall and stratified by sex. In patients who reported the exact duration of chest pain, we assessed the effect of marital status on the delay in seeking care. Results: Among 4403 eligible patients with acute myocardial infarction, the mean age was 67.3 (standard deviation 13.6) years, and 1486 (33.7%) were women. Almost half (2037 or 46.3%) presented to a hospital within two hours, and 3240 (73.6%) presented within six hours. Overall, 75.3% (2317/3079) of married patients, 67.9% (188/277) of single patients, 68.5% (189/276) of divorced patients and 70.8% (546/771) of widowed patients presented within six hours of the onset of chest pain. Being married was associated with lower odds of delayed presentation (odds ratio [OR] 0.46, 95% confidence interval [CI] 0.30–0.71, p < 0.001) relative to being single. Among men, the OR was 0.35 (95% CI 0.21–0.59, p < 0.001), whereas among women the effect of marital status was not significant (OR 1.36, 95% CI 0.49–3.73, p = 0.55). Interpretation: Among men experiencing acute myocardial infarction with chest pain, being married was associated with significantly earlier presentation for care, a benefit that was not observed for married women. Earlier presentation for medical care appears to be one reason for the observed lower risk of cardiovascular death among married men, relative to their single counterparts.

Patterns of use of thienopyridine therapy after percutaneous coronary interventions with drug-eluting stents and bare-metal stents

BACKGROUND Twelve months of uninterrupted thienopyridine therapy after drug-eluting stents (DES) implantation was recently recommended, but limited data are available regarding long-term use in clinical practice. The objective of the study was to determine the adherence to thienopyridine therapy after stent implantation, factors associated with suboptimal adherence, and association of suboptimal adherence with mortality. METHODS We evaluated 5,263 older patients (>65 years) who received DES and 6,081 older patients who received bare-metal stents (BMS) from December 1, 2003, to March 31, 2006, in Ontario, Canada, who were eligible to receive 12 months of thienopyridine at minimal cost. RESULTS Primary nonadherence was observed among 6.9% in the DES group and 7.1% in the BMS group that did not fill a single prescription of thienopyridine within 1 year of stent implantation. Premature discontinuation occurred in a progressive manner, with 28% in the DES group and 34% in the BMS group discontinuing therapy by 6 months. Low-income patients eligible for a waiver of deductible and dispensing fee were almost 70% more likely to fill their first prescription. For DES patients, primary nonadherence (hazard ratio [HR] 2.68, 95% CI 1.77-4.07), 12-months proportional days covered <80% (HR 2.39, 95% CI 1.67-3.43), and prematurely discontinuing therapy within 6 months (HR 2.64, 95% 1.60-4.35) were associated with an increased risk of death. CONCLUSIONS We found suboptimal patterns of adherence to thienopyridine therapy after DES implantation that was strongly associated with an increased mortality risk. Eliminating any costs for thienopyridine therapy may be an effective strategy to increase medication adherence.

The Incidence of Major Cardiovascular Events in Immigrants to Ontario, Canada: The CANHEART Immigrant Study.

Background —Immigrants from ethnic minority groups represent an increasing proportion of the population in many high-income countries but little is known about the causes and amount of variation between various immigrant groups in the incidence of major cardiovascular events. Methods and Results —We conducted the Cardiovascular Health in Ambulatory Care Research Team (CANHEART) Immigrant study, a big data initiative, linking information from Citizenship and Immigration Canadas Permanent Resident database to nine population-based health databases. A cohort of 824 662 first-generation immigrants aged 30 to 74 as of January 2002 from eight major ethnic groups and 201 countries of birth who immigrated to Ontario, Canada between 1985 and 2000 were compared to a reference group of 5.2 million long-term residents. The overall 10-year age-standardized incidence of major cardiovascular events was 30% lower among immigrants compared with long-term residents. East Asian immigrants (predominantly ethnic Chinese) had the lowest incidence overall (2.4 in males, 1.1 in females per 1000 person-years) but this increased with greater duration of stay in Canada. South Asian immigrants, including those born in Guyana had the highest event rates (8.9 in males, 3.6 in females per 1000 person-years), along with immigrants born in Iraq and Afghanistan. Adjustment for traditional risk factors reduced but did not eliminate differences in cardiovascular risk between various ethnic groups and long-term residents. Conclusions —Striking differences in the incidence of cardiovascular events exist among immigrants to Canada from different ethnic backgrounds. Traditional risk factors explain part but not all of these differences.Background— Immigrants from ethnic minority groups represent an increasing proportion of the population in many high-income countries, but little is known about the causes and amount of variation between various immigrant groups in the incidence of major cardiovascular events. Methods and Results— We conducted the Cardiovascular Health in Ambulatory Care Research Team (CANHEART) Immigrant Study, a big data initiative, linking information from Citizenship and Immigration Canada’s Permanent Resident database to 9 population-based health databases. A cohort of 824 662 first-generation immigrants aged 30 to 74 as of January 2002 from 8 major ethnic groups and 201 countries of birth who immigrated to Ontario, Canada between 1985 and 2000 were compared with a reference group of 5.2 million long-term residents. The overall 10-year age-standardized incidence of major cardiovascular events was 30% lower among immigrants than among long-term residents. East Asian immigrants (predominantly ethnic Chinese) had the lowest incidence overall (2.4 in males, 1.1 in females per 1000 person-years), but this increased with greater duration of stay in Canada. South Asian immigrants, including those born in Guyana, had the highest event rates (8.9 in males, 3.6 in females per 1000 person-years), along with immigrants born in Iraq and Afghanistan. Adjustment for traditional risk factors reduced but did not eliminate the differences in cardiovascular risk between various ethnic groups and long-term residents. Conclusions— Striking differences in the incidence of cardiovascular events exist among immigrants to Canada from different ethnic backgrounds. Traditional risk factors explain a part but not all of these differences.

Moving to a Highly Walkable Neighborhood and Incidence of Hypertension: A Propensity-Score Matched Cohort Study.

Background: The impact of moving to a neighborhood more conducive to utilitarian walking on the risk of incident hypertension is uncertain. Objective: Our study aimed to examine the effect of moving to a highly walkable neighborhood on the risk of incident hypertension. Methods: A population-based propensity-score matched cohort study design was used based on the Ontario population from the Canadian Community Health Survey (2001–2010). Participants were adults ≥ 20 years of age who moved from a low-walkability neighborhood (defined as any neighborhood with a Walk Score < 90) to either a high- (Walk Score ≥ 90) or another low-walkability neighborhood. The incidence of hypertension was assessed by linking the cohort to administrative health databases using a validated algorithm. Propensity-score matched Cox proportional hazard models were used. Annual health examination was used as a control event. Results: Among the 1,057 propensity-score matched pairs there was a significantly lower risk of incident hypertension in the low to high vs. the low to low-walkability groups [hazard ratio = 0.46; 95% CI, 0.26, 0.81, p < 0.01]. The crude hypertension incidence rates were 18.0 per 1,000 person-years (95% CI: 11.6, 24.8) among the low- to low-walkability movers compared with 8.6 per 1,000 person-years (95% CI: 5.3, 12.7) among the low- to high-walkability movers (p < 0.001). There were no significant differences in the hazard of annual health examination between the two mover groups. Conclusions: Moving to a highly walkable neighborhood was associated with a significantly lower risk of incident hypertension. Future research should assess whether specific attributes of walkable neighborhoods (e.g., amenities, density, land-use mix) may be driving this relationship. Citation: Chiu M, Rezai MR, Maclagan LC, Austin PC, Shah BR, Redelmeier DA, Tu JV. 2016. Moving to a highly walkable neighborhood and incidence of hypertension: a propensity-score matched cohort study. Environ Health Perspect 124:754–760; http://dx.doi.org/10.1289/ehp.1510425