Douglas G. Manuel

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.

Revisiting Rose: strategies for reducing coronary heart disease

The way we assess risk of coronary heart disease has become more accurate in recent years. How does this affect the efficacy of primary and secondary prevention strategies?

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.

Development and use of reporting guidelines for assessing the quality of validation studies of health administrative data

BACKGROUND AND OBJECTIVES Validation of health administrative data for identifying patients with different health states (diseases and conditions) is a research priority, but no guidelines exist for ensuring quality. We created reporting guidelines for studies validating administrative data identification algorithms and used them to assess the quality of reporting of validation studies in the literature. METHODS Using Standards for Reporting of Diagnostic accuracy (STARD) criteria as a guide, we created a 40-item checklist of items with which identification accuracy studies should be reported. A systematic review identified studies that validated identification algorithms using administrative data. We used the checklist to assess the quality of reporting. RESULTS In 271 included articles, goals and data sources were well reported but few reported four or more statistical estimates of accuracy (36.9%). In 65.9% of studies reporting positive predictive value (PPV)/negative predictive value (NPV), the prevalence of disease in the validation cohort was higher than in the administrative data, potentially falsely elevating predictive values. Subgroup accuracy (53.1%) and 95% confidence intervals for accuracy measures (35.8%) were also underreported. CONCLUSIONS The quality of studies validating health states in the administrative data varies, with significant deficits in reporting of markers of diagnostic accuracy, including the appropriate estimation of PPV and NPV. These omissions could lead to misclassification bias and incorrect estimation of incidence and health services utilization rates. Use of a reporting checklist, such as the one created for this study by modifying the STARD criteria, could improve the quality of reporting of validation studies, allowing for accurate application of algorithms, and interpretation of research using health administrative data.

Avoidable mortality by neighbourhood income in Canada: 25 years after the establishment of universal health insurance

Aim: To examine neighbourhood income differences in deaths amenable to medical care and public health over a 25-year period after the establishment of universal insurance for doctors and hospital services in Canada. Methods: Data for census metropolitan areas were obtained from the Canadian Mortality Database and population censuses for the years 1971, 1986, 1991 and 1996. Deaths amenable to medical care, amenable to public health, from ischaemic heart disease and from other causes were considered. Data on deaths were grouped into neighbourhood income quintiles on the basis of the census tract percentage of population below Canada’s low-income cut-offs. Results: From 1971 to 1996, differences between the richest and poorest quintiles in age-standardised expected years of life lost amenable to medical care decreased 60% (p<0.001) in men and 78% (p<0.001) in women, those amenable to public health increased 0.7% (p = 0.94) in men and 20% (p = 0.55) in women, those lost from ischaemic heart disease decreased 58% in men and 38% in women, and from other causes decreased 15% in men and 9% in women. Changes in the age-standardised expected years of life lost difference for deaths amenable to medical care were significantly larger than those for deaths amenable to public health or other causes for both men and women (p<0.001). Conclusions: Reductions in rates of deaths amenable to medical care made the largest contribution to narrowing socioeconomic mortality disparities. Continuing disparities in mortality from causes amenable to public health suggest that public health initiatives have a potentially important, but yet unrealised, role in further reducing mortality disparities in Canada.

Ascertainment of chronic diseases using population health data: a comparison of health administrative data and patient self-report

BackgroundHealth administrative data is increasingly being used for chronic disease surveillance. This study explored agreement between administrative and survey data for ascertainment of seven key chronic diseases, using individually linked data from a large population of individuals in Ontario, Canada.MethodsAll adults who completed any one of three cycles of the Canadian Community Health Survey (2001, 2003 or 2005) and agreed to have their responses linked to provincial health administrative data were included. The sample population included 85,549 persons. Previously validated case definitions for myocardial infarction, asthma, diabetes, chronic lung disease, stroke, hypertension and congestive heart failure based on hospital and physician billing codes were used to identify cases in health administrative data and these were compared with self-report of each disease from the survey. Concordance was measured using the Kappa statistic, percent positive and negative agreement and prevalence estimates.ResultsAgreement using the Kappa statistic was good or very good (kappa range: 0.66-0.80) for diabetes and hypertension, moderate for myocardial infarction and asthma and poor or fair (kappa range: 0.29-0.36) for stroke, congestive heart failure and COPD. Prevalence was higher in health administrative data for all diseases except stroke and myocardial infarction. Health Utilities Index scores were higher for cases identified by health administrative data compared with self-reported data for some chronic diseases (acute myocardial infarction, stroke, heart failure), suggesting that administrative data may pick up less severe cases.ConclusionsIn the general population, discordance between self-report and administrative data was large for many chronic diseases, particularly disease with low prevalence, and differences were not easily explained by individual and disease characteristics.

Effectiveness and efficiency of different guidelines on statin treatment for preventing deaths from coronary heart disease: modelling study

Abstract Objective To examine the potential effectiveness and efficiency of different guidelines for statin treatment to reduce deaths from coronary heart disease in the Canadian population. Design Modelled outcomes of screening and treatment recommendations of six national or international guidelines—from Canada, Australia, New Zealand, the United States, joint British societies, and European societies. Setting Canada. Data sources Details for 6760 men and women aged 20-74 years from the Canadian Heart Health Survey (weighted sample of 12 300 000 people) that included physical measurements including a lipid profile. Main outcome measures The number of people recommended for treatment with statins, the potential number of deaths from coronary heart disease avoided, and the number needed to treat to avoid one coronary heart disease death with five years of statin treatment if the recommendations from each guideline were fully implemented. Results When applied to the Canadian population, the Australian and British guidelines were the most effective, potentially avoiding the most deaths over five years (> 15 000 deaths). The New Zealand guideline was the most efficient, potentially avoiding almost as many deaths (14 700) while recommending treatment to the fewest number of people (12.9% of people v 17.3% with the Australian and British guidelines). If their “optional” recommendations are included, the US guidelines recommended treating about twice as many people as the New Zealand guidelines (24.5% of the population, an additional 1.4 million people) with almost no increase in the number of deaths avoided. Conclusions By focusing recommendations on people with the highest risk of coronary heart disease, the Canadian, US, and European societies guidelines could improve either their effectiveness (in terms of hundreds of avoided deaths) or efficiency (in terms of thousands of fewer people recommended treatment) in the Canadian population.

Measuring the health burden of chronic disease and injury using health adjusted life expectancy and the Health Utilities Index

Objectives: To estimate the burden of illness from chronic disease and injury using a population based health survey, which contains both measures of chronic disease and a utility based health related quality of life (HRQOL) measure. Design: An adapted Sullivan method was used to calculate cause deleted health adjusted life expectancies for chronic conditions. Setting: Ontario, Canada, 1996/97. Subjects: The 1996/97 Ontario Health Survey (n=35 527) was used to estimate the prevalence of chronic conditions. A cause deleted approach was used to estimate the impact of these conditions on the Health Utilities Index (HUI). Cause deleted probabilities of dying were derived with the cause eliminated life table technique and death data from vital statistics for Ontario 1996/97 (n=156 610). Results: Eliminating cardiovascular disease and cancer will cause an “expansion of morbidity”, while eliminating mental conditions and musculosketal disorders will result in a “contraction of morbidity”. The HUI score varies depending on chronic condition, age, and sex—most of which were assumed not to vary in previous summary measures of population health. Conclusions: Health adjusted life expectancy estimated for chronic conditions using a utility based measure of health related quality of life from population health surveys addresses several limitations of previous studies that estimate the burden of disease using either a categorical measure of disability or expert opinion and related epidemiological evidence.

Inflammatory Bowel Disease in Immigrants to Canada And Their Children: A Population-Based Cohort Study

OBJECTIVES:The risk of inflammatory bowel disease (IBD) contributed by the environment can be elucidated by assessing the risk in migrants from low prevalence to Western countries. The incidence of IBD in immigrants to Canada and their Canadian-born children was compared with nonimmigrants.METHODS:A population-based cohort of IBD patients derived from health administrative data was linked to immigration data to determine the standardized incidence of IBD in immigrants to Ontario, Canada, by region of birth between 1994 and 2010. The hazard contributed by younger age at immigration was determined. Incidence for Ontario-born children of immigrant mothers was compared with the children of nonimmigrants.RESULTS:In 2,144,660 immigrants, incidence of IBD was 7.3/100,000 person-years compared with 23.9/100,000 in 12,036,921 nonimmigrants (incidence rate ratio (IRR) 0.34, 95% CI 0.26–0.44). Incidence was lowest risk in East Asians (IRR 0.14, 95% CI 0.11–0.18) and highest in Western Europeans/North Americans (IRR 0.59, 95% CI 0.46–0.75). Increased age at immigration was associated with decreased risk of IBD (HR 0.986, 95% CI 0.982–0.990), a 14% increased risk per younger decade of life at immigration. Children of immigrants from the Middle East/North Africa, South Asia, Sub-Saharan Africa, and North America/Western Europe had similar risk of IBD as children of nonimmigrants; however, the incidence remained lower among children of immigrants from other regions.CONCLUSIONS:Younger age at arrival to Canada increased the risk of IBD in immigrants. Canadian-born children of immigrants from some regions assumed the high Canadian incidence of IBD, indicating that the underlying risk is activated with earlier life exposure to the Canadian environment in certain groups.