ISSN:1044-3983    

出版商:OVID    

年代:2003

数据来源: OVID

ISSN:1044-3983    

出版商:OVID    

年代:2003

数据来源: OVID

ISSN:1044-3983    

出版商:OVID    

年代:2003

数据来源: OVID

ISSN:1044-3983    

出版商:OVID    

年代:2003

数据来源: OVID

ISSN:1044-3983    

出版商:OVID    

年代:2003

数据来源: OVID

ISSN:1044-3983    

出版商:OVID    

年代:2003

数据来源: OVID

ISSN:1044-3983    

出版商:OVID    

年代:2003

数据来源: OVID

ISSN:1044-3983    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

In recent years, a number of studies have applied generalized additive models to time series data to estimate associations between exposure to air pollution and cardiorespiratory morbidity and mortality. If concurvity, the nonparametric analogue of multicollinearity, is present in the data, statistical software such as S-plus can seriously underestimate the variance of fitted model parameters, leading to significance tests with inflated type 1 error. This paper uses computer simulation and analyses of actual epidemiologic data to explore this underestimation of standard errors. We provide a method for assessing concurvity in data and an alternate class of models that is unaffected by concurvity. We argue that some degree of concurvity is likely to be present in all epidemiologic time series datasets and we explore through the use of meta-analysis the possible impact of concurvity on the existing body of work relating ambient levels of sulfate particles to mortality.

ISSN:1044-3983    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

Background.To study the impact of smoking and blood pressure conditional on serum total cholesterol levels, we investigated the 20-year mortality risk associated with high systolic blood pressure (≥140 mmHg) and smoking, at low (<5.2 mmol/Liter), medium (5.2–6.49mmol/Liter), and high (≥6.5 mmol/Liter) serum total cholesterol levels.Methods.The study population comprised a cohort of 50,000 men and women age 30–54 years, examined between 1974 and 1980, in five Dutch towns. The duration of follow-up averaged 20 years. Age-adjusted relative risks (RRs) for mortality from coronary heart disease (CHD), cardiovascular diseases (CVD) and all causes were estimated, for six risk profiles (based on levels of total cholesterol, systolic blood pressure and smoking), using Cox proportional hazards analysis.Results.Given a low cholesterol level, smoking had a larger impact than elevated blood pressure on CHD, CVD and all-cause mortality. The combination of elevated blood pressure and smoking among persons with low cholesterol was associated with RRs of 3.0 for CHD, 6.0 for CVD and 4.1 for all-cause mortality in men, and 2.3, 3.6 and 2.6, respectively, in women. Among persons with high cholesterol, the combination of high blood pressure and smoking was associated with RRs of 9.7 for CHD, 13.9 for CVD and 5.7 for all-cause mortality in men, and 15.9, 9.3 and 4.3, respectively, in women. For each risk profile, the absolute number of CHD, CVD and total deaths was larger in men than in women.Conclusions.The results demonstrate the potential power of a multifactorial approach to risk factor reduction in the prevention of cardiovascular diseases and all-cause mortality.

ISSN:1044-3983    

出版商:OVID    

年代:2003

数据来源: OVID