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:

Background:Nitrate is a widespread contaminant of drinking water, but its potential health effects are unclear. In the body, nitrate is reduced to nitrite, which can react with amines and amides by nitrosation to form N-nitroso compounds, known animal carcinogens. N-nitroso compound formation is inhibited by certain nutrients, such as vitamin C, and increased by meat intake.Methods:We investigated the association of nitrate in public water supplies with incident colon and rectum cancers in a case-control study conducted in Iowa from 1986 to 1989. Nitrate levels in Iowa towns were linked to the participants’ water source histories. We focused our analyses on the period from 1960 onward, during which nitrate measurements were more frequent, and we restricted analyses to those persons with public water supplies that had nitrate data (actual or imputed) for greater than 70% of this time period (376 colon cancer cases, 338 rectum cancer cases, and 1244 controls).Results:There were negligible overall associations of colon or rectum cancers with measures of nitrate in public water supplies, including average nitrate and the number of years with elevated average nitrate levels. For more than 10 years with average nitrate greater than 5 mg/L, the odds ratio (OR) for colon cancer was 1.2 (95% confidence interval [CI] = 0.9–1.6) and for rectum the OR was 1.1 (CI = 0.7–1.5). However, nitrate exposure (>10 years with average nitrate >5 mg/L) was associated with increased colon cancer risk among subgroups with low vitamin C intake (OR = 2.0; CI = 1.2–3.3) and high meat intake (OR = 2.2; CI = 1.4–3.6). These patterns were not observed for rectum cancer.Conclusions:Our analyses suggest that any increased risk of colon cancer associated with nitrate in public water supplies might occur only among susceptible subpopulations.

ISSN:1044-3983    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

Background:Trihalomethanes (THMs) are byproducts of drinking water chlorination whose effects on semen quality have not been previously studied in humans.Methods:We examined the relationship of THMs to semen quality in 157 healthy men from couples without known risk factors for infertility. Total THM (TTHM) levels were assigned based on water utility measurements taken during the 90 days preceding semen collection. We analyzed continuous semen parameters in relation to total and individual THMs, adjusting for potential confounders by using repeated measures analyses.Results:TTHM level was not associated with decrements in semen quality. Percent normal morphology decreased and percent head defects increased at higher levels of an ingestion metric (TTHM multiplied by cold home tap water consumption). At the highest level of the ingestion metric (>160 &mgr;g/L × glasses/day, which is equivalent to >2 glasses/day of water containing 80 &mgr;g/L) we observed a difference of −7.1 (95% confidence interval = −12.7 to −1.6) for percent morphologically normal sperm compared with the lowest level (≤ 40 &mgr;g/L × glasses/day). Of the individual THMs, bromodichloromethane exposure was inversely related to linearity (a motility parameter); we observed a small decrease (&bgr; = −0.09, SE 0.04) for every unit increase in bromodichloromethane.Conclusion:Although our study had a limited exposure assessment and a selective sample, our results suggest the need for further study of the effects of THMs on semen quality.

ISSN:1044-3983    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

Background:High fruit and vegetable consumption has been associated with a lower risk of cardiovascular diseases, but few studies have focused on peripheral arterial disease. In this study, we evaluated the association of consumption of fruits and vegetables with peripheral arterial disease.Methods:In a cohort of 44,059 men initially free of cardiovascular disease and diabetes, we documented 295 cases of peripheral arterial disease during a 12-year follow-up. Fruit and vegetable consumption was assessed by food frequency questionnaire.Results:In the age-adjusted model, men in the highest quintile had a relative risk of 0.55 (95% confidence interval = 0.38–0.80) for overall fruit and vegetable intake, 0.52 (0.36–0.77) for fruit intake, and 0.54 (0.36–0.81) for vegetable intake, compared with those in the lowest quintile of intake. However, the associations were greatly weakened after adjustment for smoking and other traditional cardiovascular disease risk factors. Comparing men in the highest quintile versus the lowest quintile, relative risks and 95% confidence intervals were 0.95 (0.62–1.44) for overall fruit and vegetable intake, 0.97 (0.64–1.48) for fruit intake, and 0.76 (0.50–1.17) for vegetable intake.Conclusions:We did not find evidence that fruit and vegetable consumption protects against peripheral arterial disease, although a modest benefit cannot be excluded.

ISSN:1044-3983    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

Background:Atrial fibrillation is a common arrhythmia associated with excess morbidity and mortality. We studied temporal changes in hospital admission rates for atrial fibrillation using data from a prospective population-based cohort study spanning 2 decades (the Copenhagen City Heart Study).Methods:The study included baseline data collected in 1981 through 1983 on 10,955 persons age 40 to 79 years and baseline data collected in 1991 through 1994 on 7212 persons age 40 to 79 years. We used hospital diagnosis data from the Danish National Hospital Discharge Register to determine the rate of first hospital admission for atrial fibrillation during 7 years following each of the 2 baseline data collecting periods. Changes in admission rates were analyzed using Cox proportional hazard models.Results:During the 2 7-year periods, 379 subjects were admitted with a hospital diagnosis of atrial fibrillation. The rate of hospital admissions for atrial fibrillation increased among both men and women from the first to the second period (relative risk = 1.6; 95% confidence interval = 1.3–1.9 [adjusted for age, sex, prior myocardial infarction, arterial hypertension, diabetes mellitus, electrocardiographic left ventricular hypertrophy, decreased lung function, smoking, height, and weight]).Conclusion:During the latest 10 to 20 years, there has been a 60% increase in hospital admissions for atrial fibrillation independent of changes in known risk factors. This increase could result from changes in admission threshold or coding practices, or it could reflect a genuine increase in the population incidence of atrial fibrillation.

ISSN:1044-3983    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

Background:Some studies have suggested that cognitive impairment is related to subsequent stroke incidence. The present study investigated the role of cognitive impairment as a predictor of ischemic stroke incidence in the Atherosclerosis Risk in Communities (ARIC) cohort.Methods:The study population consisted of 11,958 men and women 48-67 years of age in 4 U.S. communities, followed from January 1, 1990 through December 31, 1997. Cognitive performance was evaluated at the second (1990–1992) visit of the ARIC Study using 3 instruments. We identified incident strokes by means of hospital record and death certificate reviews, as well as annual telephone follow up.Results:We found no consistent associations or trends between any of the cognitive test results and ischemic stroke incidence after multiple adjustment for confounding variables. Hazard ratios for the lowest compared with the highest quartiles were 1.5 (95% confidence interval [CI] = 0.9–2.6), 1.1 (95% CI = 0.6–2.1), and 1.0 (95% CI = 0.6-1.8) for the Delayed Word Recall Test, Digit Symbol Subtest of the Wechsler Adult Intelligence Scale–Revised, and Word Fluency Test, respectively.Conclusions:The findings of the present study of relatively young subjects did not replicate the association between cognitive impairment and stroke incidence found in studies in older populations. This could be the result of the younger ages of our cohort members or the differences in cognitive tests.

ISSN:1044-3983    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

In this article, we show the general relation between standardization methods and marginal structural models. Standardization has been recognized as a method to control confounding and to estimate causal parameters of interest. Because standardization requires stratification by confounders, the sparse-data problem will occur when stratified by many confounders and one then might have an unstable estimator. A new class of causal models called marginal structural models has recently been proposed. In marginal structural models, the parameters are consistently estimated by the inverse-probability-of-treatment weighting method. Marginal structural models give a nonparametric standardization using the total group (exposed and unexposed) as the standard. In epidemiologic analysis, it is also important to know the change in the average risk of the exposed (or the unexposed) subgroup produced by exposure, which corresponds to the exposed (or the unexposed) group as the standard. We propose modifications of the weights in the marginal structural models, which give the nonparametric estimation of standardized parameters. With the proposed weights, we can use the marginal structural models as a useful tool for the nonparametric multivariate standardization.

ISSN:1044-3983    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

BackgroundA U.S. analysis suggested a relation between self-reported residential proximity to industrial plants and non-Hodgkin lymphoma (NHL) risk.MethodsUsing lifetime residential histories collected from a population-based sample of 1499 Canadians with newly diagnosed, histologically confirmed NHL and 5039 population controls, we evaluated the association of residential proximity to 7 types of major heavy industry with NHL risk.ResultsOverall, having lived within 0.8 km or within 3.2 km of an industrial plant was not associated with increased NHL risk. For the follicular subtype of NHL, an odds ratio (OR) of 1.48 (95% confidence interval [CI] = 1.10–1.99) was observed for women who had lived within 3.2 km (83 cases/689 controls). ORs for NHL were elevated for proximity within 3.2 km of copper smelters (OR = 5.1; CI = 1.5–17.7; 7 cases, 4 controls) and within 0.8 km of sulfite pulp mills (OR = 3.7; CI = 1.5–9.4; 9 cases, 10 controls).ConclusionsWe have identified possible associations between NHL and proximity to industrial plants, which could be the result of chance or other factors associated with proximity. Studies are needed to confirm these associations and to determine whether residential proximity can result in meaningful exposure.

ISSN:1044-3983    

出版商:OVID    

年代:2003

数据来源: OVID