448 research outputs found
Comparing measurement error correction methods for rate-of-change exposure variables in survival analysis
No full textIn this article we focus on comparing measurement error correction methods for rate-of-change exposure variables in survival analysis, when longitudinal data are observed prior to the follow-up time. Motivational examples include the analysis of the association between changes in cardiovascular risk factors and subsequent onset of coronary events. We derive a measurement error model for the rate of change, estimated through subject-specific linear regression, assuming an additive measurement error model for the time-specific measurements. The rate of change is then included as a time-invariant variable in a Cox proportional hazards model, adjusting for the first time-specific measurement (baseline) and an error-free covariate. In a simulation study, we compared bias, standard deviation and mean squared error (MSE) for the regression calibration (RC) and the simulation-extrapolation (SIMEX) estimators. Our findings indicate that when the amount of measurement error is substantial, RC should be the preferred method, since it has smaller MSE for estimating the coefficients of the rate of change and of the variable measured without error. However, when the amount of measurement error is small, the choice of the method should take into account the event rate in the population and the effect size to be estimated. An application to an observational study, as well as examples of published studies where our model could have been applied, are also provided
Reliability of bodyfat distribution measurements. The ARIC Study Baseline Cohort results.
No full textUn metodo per ricalibrare funzioni predittive basate sul modello dei rischi proporzionali
No full textExplaining the occupational class differences in CHD incidence: the contribution of major risk factors and job strain.
No full textTemporal Trends in Ischemic and Hemorrhagic Strokes in Northern Italy: Results from the Cardiovascular Monitoring Unit in Northern Italy Population. Based Register, 1998-2004.
No full textBackground: We compared rates and case fatality from a population-based stroke register in Northern Italy between 1998 and 2004 to assess changes over time and to evaluate changes in case diagnosis and management. Methods: The WHO Multinational Monitoring of Trends and Determinants in Cardiovascular Disease criteria were used to identify suspected fatal or nonfatal events occurring among residents 35-74 years of age. Data on in-hospital treatments, symptoms and diagnostic tools were extracted. Out-of-hospital deaths were also investigated. The annual average relative change (ARC) in death rate, attack rate and case fatality were derived from Poisson models. Results: Death rates due to ischemic stroke (IS) decreased [men: ARC -12.7, 95% confidence interval (CI) -21.3 to -3.2; women: ARC -14.0, 95% CI -23.3 to -3.5]. These reductions are attributable to decreases in case fatality; attack rates of nonfatal IS increased (men: ARC 3.6, 95% CI 0.5-6.7; women: ARC 4.1, 95% CI 0.0-8.2). IS patients showed a higher prevalence of dyslipidemia and hypertension and underwent MRI more frequently in 2004. Both findings may explain the increased proportions of less severe cases. Case fatality and attack rates for hemorrhagic strokes (HS) were stable, with an observed increased prevalence of patients under anticoagulant/antiplatelet treatments. Conclusions: In this low-IS-incidence population, death rates decreased substantially during the investigated period. More accurate diagnostic tools increase the probability of detecting less severe cases. HS remains a frequently fatal disease with a stable incidence
[Photograph 2012.201.B1258.0776]
No full textPhotograph used for a newspaper owned by the Oklahoma Publishing Company. Caption: "Orville L. Chambless
Adolescent regulation of strong emotions: Age and gender differences
No full textAdolescents’ capacity to regulate strong emotions is an important aspect of successful adolescent development. To date, no measure has been available to assess adolescents’ ability to regulate their strong emotions. This study used the MACS, an adapted version of the Affective Control Scale (Chambless & Williams, 1982), to survey over 2100 high school students, aged 12-18 years. A further 1200 of these completed a follow-up survey. The findings indicated that, in general, males had an increased fear of positive emotion and anger, whereas females had an increased fear of negative emotions of depression and anxiety. Females were also less able than males to take charge of their strong emotions. In addition, fear of negative emotions was greatest for girls aged 14 years. The MACS proved to be a useful and dependable way of ascertaining adolescents’ emotional functioning
Population versus clinical view of case fatality from acute coronary heart disease. Results from the WHO-MONICA project.
No full textBackground The clinical view of case fatality (CF) from acute myocardial infarction (AMI) in those reaching the hospital alive is different from the population view. Registration of both hospitalized AMI cases and out-of-hospital coronary heart disease (CHD) deaths in the WHO MONICA Project allows both views to be reconciled. The WHO MONICA Project provides the largest data set worldwide to explore the relationship between CHD CF and age, sex, coronary event rate, and first versus recurrent event.
Methods and Results All 79 669 events of definite AMI or possible coronary death, occurring from 1985 to 90 among 5 725 762 people, 35 to 64 years of age, in 29 MONICA populations are the basis for CF calculations. Age-adjusted CF (percentage of CHD events that were fatal) was calculated across populations, stratified for different time periods, and related to age, sex, and CHD event rate. Median 28-day population CF was 49% (range, 35% to 60%) in men and 51% (range, 34% to 70%) in women and was particularly higher in women than men in populations in which CHD event rates were low. Median 28-day CF for hospitalized events was much lower: in men 22% (range, 15% to 36%) and in women 27% (range, 19% to 46%). Among hospitalized events CF was twice as high for recurrent as for first events.
Conclusions Overall 28-day CF is halved for hospitalized events compared with all events and again nearly halved for hospitalized 24-hour survivors. Because approximately two thirds of 28-day CHD deaths in men and women occurred before reaching the hospital, opportunities for reducing CF through improved care in the acute event are limited. Major emphasis should be on primary and secondary prevention
Improving long-term prediction of first cardiovascular event: The contribution of family history of coronary heart disease and social status
No full textObjective: The aim of this study is to assess whether family history of coronary heart disease (CHD) and education as proxy of social status improve long-term cardiovascular disease risk prediction in a low-incidence European population. Methods: The 20-year risk of first coronary or ischemic stroke events was estimated using sex-specific Cox models in 3956 participants of three population-based surveys in northern Italy, aged 35-69. years and free of cardiovascular disease at enrollment. The additional contribution of education and positive family history of CHD was defined as change in discrimination and Net Reclassification Improvement (NRI) over the model including 7 traditional risk factors. Results: Kaplan-Meier 20-year risk was 16.8% in men (254 events) and 6.4% in women (102 events). Low education (hazard ratio. =. 1.35, 95%CI 0.98-1.85) and family history of CHD (1.55; 1.19-2.03) were associated with the endpoint in men, but not in women. In men, the addition of education and family history significantly improved discrimination by 1%; NRI was 6% (95%CI: 0.2%-15.2%), raising to 20% (0.5%-44%) in those at intermediate risk. NRI in women at intermediate risk was 7%. Conclusion: In low-incidence populations, family history of CHD and education, easily assessed in clinical practice, should be included in long-term cardiovascular disease risk scores, at least in men
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