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Michal Abrahamowicz

Bio: Michal Abrahamowicz is an academic researcher from McGill University. The author has contributed to research in topics: Population & Hazard ratio. The author has an hindex of 80, co-authored 401 publications receiving 23871 citations. Previous affiliations of Michal Abrahamowicz include Université de Sherbrooke & International Agency for Research on Cancer.


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Journal ArticleDOI
TL;DR: This new sex-specific, population-based reference should improve clinical assessment of growth in individual newborns, population -based surveillance of geographic and temporal trends in birth weight for gestational age, and evaluation of clinical or public health interventions to enhance fetal growth.
Abstract: Background. Existing fetal growth references all suffer from 1 or more major methodologic problems, including errors in reported gestational age, biologically implausible birth weight for gestational age, insufficient sample sizes at low gestational age, single-hospital or other non-population–based samples, and inadequate statistical modeling techniques. Methods. We used the newly developed Canadian national linked file of singleton births and infant deaths for births between 1994 and 1996, for which gestational age is largely based on early ultrasound estimates. Assuming a normal distribution for birth weight at each gestational age, we used the expectation-maximization algorithm to exclude infants with gestational ages that were more consistent with 40-week births than with the observed gestational age. Distributions of birth weight at the corrected gestational ages were then statistically smoothed. Results. The resulting male and female curves provide smooth and biologically plausible means, standard deviations, and percentile cutoffs for defining small- and large-for-gestational-age births. Large-for-gestational age cutoffs (90th percentile) at low gestational ages are considerably lower than those of existing references, whereas small-for-gestational-age cutoffs (10th percentile) postterm are higher. For example, compared with the current World Health Organization reference from California (Williams et al, 1982) and a recently proposed US national reference (Alexander et al, 1996), the 90th percentiles for singleton males at 30 weeks are 1837 versus 2159 and 2710 g. The corresponding 10th percentiles at 42 weeks are 3233 versus 3086 and 2998 g. Conclusions. This new sex-specific, population-based reference should improve clinical assessment of growth in individual newborns, population-based surveillance of geographic and temporal trends in birth weight for gestational age, and evaluation of clinical or public health interventions to enhance fetal growth. fetal growth, birth weight, gestational age, preterm birth, postterm birth.

1,439 citations

Journal ArticleDOI
TL;DR: There is a substantial and statistically significant increase in CHD and stroke in SLE that cannot be fully explained by traditional Framingham risk factors alone.
Abstract: Objective The frequency of coronary heart disease (CHD) and stroke are increased in systemic lupus erythematosus (SLE), but the extent of the increase is uncertain. We sought to determine to what extent the increase could not be explained by common risk factors. Methods The participants at two SLE registries were assessed retrospectively for the baseline level of the Framingham study risk factors and for the presence of vascular outcomes: nonfatal myocardial infarction (MI), death due to CHD, overall CHD (nonfatal MI, death due to CHD, angina pectoris, and congestive heart failure due to CHD), and stroke. For each patient, the probability of the given outcome was estimated based on the individual's risk profile and the Framingham multiple logistic regression model, corrected for observed followup. Ninety-five percent confidence intervals (95% CIs) were estimated by bootstrap techniques. Results Of 296 SLE patients, 33 with a vascular event prior to baseline were excluded. Of the 263 remaining patients, 34 had CHD events (17 nonfatal MIs, 12 CHD deaths) and 16 had strokes over a mean followup period of 8.6 years. After controlling for common risk factors at baseline, the increase in relative risk for these outcomes was 10.1 for nonfatal MI (95% CI 5.8–15.6), 17.0 for death due to CHD (95% CI 8.1–29.7), 7.5 for overall CHD (95% CI 5.1–10.4), and 7.9 for stroke (95% CI 4.0–13.6). Conclusion There is a substantial and statistically significant increase in CHD and stroke in SLE that cannot be fully explained by traditional Framingham risk factors alone.

1,143 citations

Journal ArticleDOI
TL;DR: D Deaths in CHD have shifted away from infants and towards adults, with a steady increase in age at death and decreasing mortality, and gains in survival were mostly driven by reduced mortality in severe forms of CHD.

721 citations

Journal ArticleDOI
TL;DR: Delirium is an independent marker for increased mortality among older medical inpatients during the 12 months after hospital admission and is a particularly important prognostic marker among patients without dementia.
Abstract: Background Delirium has not been found to be a significant predictor of postdischarge mortality, but previous research has methodologic limitations including small sample sizes and inadequate control of confounding. This study aimed to determine the independent effects of presence of delirium, type of delirium (incident vs prevalent), and severity of delirium symptoms on 12-month mortality among older medical inpatients. Methods A prospective, observational study of 2 cohorts of medical inpatients was conducted with patients 65 years or older: 243 patients had prevalent or incident delirium, and 118 controls had no delirium. Baseline measures included presence of delirium and/or dementia, severity of delirium symptoms, physical function, comorbidity, and physiological and clinical severity of illness. Mortality during the 12 months after enrollment was analyzed with the Cox proportional hazards model with adjustment for covariates. Results The unadjusted hazard ratio of delirium with mortality was 3.44 (95% confidence interval, 2.05-5.75); the adjusted hazard ratio was 2.11 (95% confidence interval, 1.18-3.77). The effect of delirium was sustained over the entire 12-month period after adjustment for covariates and was stronger among patients without dementia. Among patients with dementia, there was a weak, nonsignificant effect of delirium on survival. After adjustment for covariates, mortality did not differ between patients with incident and prevalent delirium, but among patients with delirium without dementia, greater severity of delirium symptoms was associated with higher mortality. Conclusions Delirium is an independent marker for increased mortality among older medical inpatients during the 12 months after hospital admission. It is a particularly important prognostic marker among patients without dementia.

626 citations

Journal ArticleDOI
TL;DR: In this paper, the authors developed a series of structured tasks to objectively measure laparoscopic skills and used a linear regression model to test for the effects of level of training and practice on performance.
Abstract: Background: Interest in the training and evaluation of laparoscopic skills is extending beyond the realm of the operating room to the use of laparoscopic simulators. The purpose of this study was to develop a series of structured tasks to objectively measure laparoscopic skills. This model was then used to test for the effects of level of training and practice on performance. Methods: Forty-two subjects (6 each of surgical residents PGY1 to PGY5, 6 surgeons who practice laparoscopy and 6 who do not) were evaluated. Each subject viewed a 20-minute introductory video, then was tested performing 7 laparoscopic tasks (peg transfers, pattern cutting, clip and divide, endolooping, mesh placement and fixation, suturing with intracorporeal or extracorporeal knots). Performance was measured using a scoring system rewarding precision and speed. Each candidate repeated all 7 tasks and was rescored. Data were analyzed by linear regression to assess the relationship of performance with level of residency training for each task, and by ANOVA with repeated measures to test for effects of level of training, of repetition, and of the interaction between level of training and repetition on overall performance. Student's t test was used to evaluate differences between laparoscopic and nonlaparoscopic surgeons and between each of these groups and the PGY 5 level of surgical residents. Results: Significant predictors of overall performance were (a) level of training ( P = 0.002), (b) repetition ( P P = 0.001). There was also a significant interaction between level of training and the specific task on performance scores ( P = 0.006). When each task was evaluated individually for the 30 residents, 4 of the 7 tasks (tasks 1, 2, 6, 7) showed significant correlation between PGY level and score. A significant difference in performance scores between laparoscopic and nonlaparoscopic surgeons was seen for tasks 1, 2, and 6. Conclusions: A model was developed to evaluate laparoscopic skills. Construct validity was demonstrated by measuring significant improvement in performance with increasing residency training, and with practice. Further validation will require correlation of performance in the model with skill in vivo.

606 citations


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TL;DR: A simple coronary disease prediction algorithm was developed using categorical variables, which allows physicians to predict multivariate CHD risk in patients without overt CHD.
Abstract: Background—The objective of this study was to examine the association of Joint National Committee (JNC-V) blood pressure and National Cholesterol Education Program (NCEP) cholesterol categories with coronary heart disease (CHD) risk, to incorporate them into coronary prediction algorithms, and to compare the discrimination properties of this approach with other noncategorical prediction functions. Methods and Results—This work was designed as a prospective, single-center study in the setting of a community-based cohort. The patients were 2489 men and 2856 women 30 to 74 years old at baseline with 12 years of follow-up. During the 12 years of follow-up, a total of 383 men and 227 women developed CHD, which was significantly associated with categories of blood pressure, total cholesterol, LDL cholesterol, and HDL cholesterol (all P,.001). Sex-specific prediction equations were formulated to predict CHD risk according to age, diabetes, smoking, JNC-V blood pressure categories, and NCEP total cholesterol and LDL cholesterol categories. The accuracy of this categorical approach was found to be comparable to CHD prediction when the continuous variables themselves were used. After adjustment for other factors, ’28% of CHD events in men and 29% in women were attributable to blood pressure levels that exceeded high normal ($130/85). The corresponding multivariable-adjusted attributable risk percent associated with elevated total cholesterol ($200 mg/dL) was 27% in men and 34% in women. Conclusions—Recommended guidelines of blood pressure, total cholesterol, and LDL cholesterol effectively predict CHD risk in a middle-aged white population sample. A simple coronary disease prediction algorithm was developed using categorical variables, which allows physicians to predict multivariate CHD risk in patients without overt CHD. (Circulation. 1998;97:1837-1847.)

9,227 citations

Journal ArticleDOI
06 Mar 2002-JAMA
TL;DR: Fine particulate and sulfur oxide--related pollution were associated with all-cause, lung cancer, and cardiopulmonary mortality and long-term exposure to combustion-related fine particulate air pollution is an important environmental risk factor for cardiopULmonary and lung cancer mortality.
Abstract: ContextAssociations have been found between day-to-day particulate air pollution and increased risk of various adverse health outcomes, including cardiopulmonary mortality. However, studies of health effects of long-term particulate air pollution have been less conclusive.ObjectiveTo assess the relationship between long-term exposure to fine particulate air pollution and all-cause, lung cancer, and cardiopulmonary mortality.Design, Setting, and ParticipantsVital status and cause of death data were collected by the American Cancer Society as part of the Cancer Prevention II study, an ongoing prospective mortality study, which enrolled approximately 1.2 million adults in 1982. Participants completed a questionnaire detailing individual risk factor data (age, sex, race, weight, height, smoking history, education, marital status, diet, alcohol consumption, and occupational exposures). The risk factor data for approximately 500 000 adults were linked with air pollution data for metropolitan areas throughout the United States and combined with vital status and cause of death data through December 31, 1998.Main Outcome MeasureAll-cause, lung cancer, and cardiopulmonary mortality.ResultsFine particulate and sulfur oxide–related pollution were associated with all-cause, lung cancer, and cardiopulmonary mortality. Each 10-µg/m3 elevation in fine particulate air pollution was associated with approximately a 4%, 6%, and 8% increased risk of all-cause, cardiopulmonary, and lung cancer mortality, respectively. Measures of coarse particle fraction and total suspended particles were not consistently associated with mortality.ConclusionLong-term exposure to combustion-related fine particulate air pollution is an important environmental risk factor for cardiopulmonary and lung cancer mortality.

7,803 citations

Journal ArticleDOI
19 Jun 2004-BMJ
TL;DR: A system for grading the quality of evidence and the strength of recommendations that can be applied across a wide range of interventions and contexts is developed, and a summary of the approach from the perspective of a guideline user is presented.
Abstract: Users of clinical practice guidelines and other recommendations need to know how much confidence they can place in the recommendations Systematic and explicit methods of making judgments can reduce errors and improve communication We have developed a system for grading the quality of evidence and the strength of recommendations that can be applied across a wide range of interventions and contexts In this article we present a summary of our approach from the perspective of a guideline user Judgments about the strength of a recommendation require consideration of the balance between benefits and harms, the quality of the evidence, translation of the evidence into specific circumstances, and the certainty of the baseline risk It is also important to consider costs (resource utilisation) before making a recommendation Inconsistencies among systems for grading the quality of evidence and the strength of recommendations reduce their potential to facilitate critical appraisal and improve communication of these judgments Our system for guiding these complex judgments balances the need for simplicity with the need for full and transparent consideration of all important issues

7,608 citations

Journal ArticleDOI
01 May 2014
TL;DR: There is substantial global variation in the relative burden of stroke compared with IHD, and the disproportionate burden from stroke for many lower-income countries suggests that distinct interventions may be required.
Abstract: Background—Although stroke and ischemic heart disease (IHD) have several well-established risk factors in common, the extent of global variation in the relative burdens of these forms of vascular disease and reasons for any observed variation are poorly understood. Methods and Results—We analyzed mortality and disability-adjusted life-year loss rates from stroke and IHD, as well as national estimates of vascular risk factors that have been developed by the World Health Organization Burden of Disease Program. National income data were derived from World Bank estimates. We used linear regression for univariable analysis and the Cuzick test for trends. Among 192 World Health Organization member countries, stroke mortality rates exceeded IHD rates in 74 countries (39%), and stroke disability-adjusted life-year loss rates exceeded IHD rates in 62 countries (32%). Stroke mortality ranged from 12.7% higher to 27.2% lower than IHD, and stroke disability-adjusted life-year loss rates ranged from 6.2% higher to 10.2% lower than IHD. Stroke burden was disproportionately higher in China, Africa, and South America, whereas IHD burden was higher in the Middle East, North America, Australia, and much of Europe. Lower national income was associated with higher relative mortality (P 0.001) and burden of disease (P 0.001) from stroke. Diabetes mellitus prevalence and mean serum cholesterol were each associated with greater relative burdens from IHD even after adjustment for national income. Conclusions—There is substantial global variation in the relative burden of stroke compared with IHD. The disproportionate burden from stroke for many lower-income countries suggests that distinct interventions may be required. (Circulation. 2011; 124:314-323.)

7,265 citations