摘要:

Background.Over 6 million people live in areas of West Bengal, India, where groundwater sources are contaminated with naturally occurring arsenic. The key objective of this nested case-control study was to characterize the dose-response relation between low arsenic concentrations in drinking water and arsenic-induced skin keratoses and hyperpigmentation.Methods.We selected cases (persons with arsenic-induced skin lesions) and age- and sex-matched controls from participants in a 1995–1996 cross-sectional survey in West Bengal. We used a detailed assessment of arsenic exposure that covered at least 20 years. Participants were reexamined between 1998 and 2000. Consensus agreement by four physicians reviewing the skin lesion photographs confirmed the diagnosis in 87% of cases clinically diagnosed in the field.Results.The average peak arsenic concentration in drinking water was 325 &mgr;g/liter for cases and 180 &mgr;g/liter for controls. The average latency for skin lesions was 23 years from first exposure. We found strong dose-response gradients with both peak and average arsenic water concentrations.Conclusions.The lowest peak arsenic ingested by a confirmed case was 115 &mgr;g/liter. Confirmation of case diagnosis and intensive longitudinal exposure assessment provide the basis for a detailed dose-response evaluation of arsenic-caused skin lesions.

ISSN:1044-3983    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

Background.Nitrate is a precursor compound in the formation of N-nitroso compounds, most of which are potent animal carcinogens. N-nitroso compounds and their precursors have not been extensively evaluated as bladder cancer risk factors.Methods.We conducted a population-based case-control study of bladder cancer in Iowa. Cases were men and women newly diagnosed with bladder cancer in 1986–1989. Nitrate data for Iowa public water supplies were sparse before the 1960s. To reduce misclassification by unknown nitrate levels, we included only those who used public supplies with nitrate data for 70% or more of their person-years since 1960 (808 cases, 1259 controls).Results.Among controls, the median average nitrate level for their Iowa residences with public water supplies was 1.3 mg/liter nitrate-nitrogen (interquartile range = 0.6–3.0). After adjustment for confounders, we found no increased risk of bladder cancer with increasing average nitrate levels in drinking water; the highest quartile odds ratio for women was 0.8 (95% confidence interval = 0.4–0.8), and for men 0.5 (0.4–0.8). We observed no association among those with high water nitrate exposure (>median) and low (<median) vitamin C intake compared with those who had low water nitrate and high vitamin C intake.Conclusions.Our data suggest that long-term exposure to nitrate in drinking water at levels in this study (90th percentile 5.5 mg/liter nitrate-nitrogen) is not associated with risk of bladder cancer.

ISSN:1044-3983    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

Background.Concerns about potential health effects of trihalomethanes (THMs) have prompted investigations on whether infants whose mothers were periconceptionally exposed to drinking water containing THMs are at greater risk of congenital malformations.Methods.We used two large case-control maternal interview studies that were conducted among California deliveries from 1987 through 1991. One study comprised 538 infants/fetuses with neural tube defects (NTDs) and 539 nonmalformed control infants. The second study included an additional 265 infants with NTDs, 207 infants with conotruncal heart defects, 409 infants with orofacial clefts, and 481 control infants. Expert personnel from municipal water companies estimated THM levels for a particular residence and specific periconceptional time period using quarterly monitoring measurements. Estimates were also made for four individual THM levels and for the total THM level.Results.NTD risk in the first study was inversely associated with total THM exposure. Although the second study did not show the same inverse relationship for NTDs, there were no positive associations of NTDs or the other malformations with total THM as estimated from continuous models. Elevated risks were observed for the lowest category of exposure (1–24 ppb), but risks were either not substantially elevated or were imprecise for higher exposure levels. Thus no evidence was observed for an exposure-response relation.Conclusions.Our results do not provide a clear pattern of association between THM exposure and risks of specific congenital malformations. Imprecise exposure measures coupled with a lack of information about other possible sources of THM exposure may have caused associations to be underestimated.

ISSN:1044-3983    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

Background.Studies have shown that folic acid supplementation in early pregnancy markedly reduces the risk of neural tube defects (NTDs). Investigation of the relation between relative dose of supplemental folic acid or total folate intake and NTD risk is limited.Methods.We used data from 23,228 women, predominantly from the northeastern United States, enrolled between October 1984 and June 1987 in a prospective study of early prenatal exposures and pregnancy outcomes. Diet and vitamin intake data were gathered in the early second trimester. NTDs were ascertained through prenatal testing and by report of the delivering physician. Data analyses included multiple logistic regression and restricted spline regression modeling.Results.For each additional 500 dietary folate equivalents consumed per day, the prevalence of NTDs decreased by 0.78 cases (95% confidence interval [CI] = 0.47–1.09) per 1,000 pregnancies. Compared with women having the lowest total folate intakes (0–149 folate equivalents per day), the prevalence of NTDs declined by 34%, 30%, 56% and 77% among the offspring of those women consuming 150–399, 400–799, 800–1199 and ≥ 1200 folate equivalents per day, respectively (P-value for linear trend = 0.016).Conclusions.Our results suggest that NTD risk declines markedly with modest increases of total folate in early pregnancy. Total folate dose, rather than supplemental folate alone, should be considered in formulating public health guidelines for NTD prevention.

ISSN:1044-3983    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

Background.Pregnancy and breastfeeding mobilize lead stored in bone, which may be a hazard for the fetus and infant. We tested the hypothesis that in lactating women a dietary calcium supplement will lower blood lead levels.Methods.Between 1994 and 1995 we conducted a randomized trial among women in Mexico City. Lactating women (N = 617; mean age = 24 years; mean blood lead level = 8.5 ug/dL) were randomly assigned to receive either calcium carbonate (1200 mg of elemental calcium daily) or placebo in a double-blind trial. Blood samples were obtained at baseline, and 3 and 6 months after the trial began. Blood lead was determined by graphite furnace atomic absorption spectroscopy. Bone lead was measured at baseline with a 109cd K x-ray fluorescence instrument. The primary endpoint was change in maternal blood lead level, which was analyzed in relation to supplement use and other covariates by multivariate generalized linear models for longitudinal observations.Results.An intention-to-treat analysis showed that women randomized to the calcium supplements experienced a small decline in blood lead levels (overall reduction of 0.29 ug/dL; 95% confidence interval = −0.85 to 0.26). The effect was more apparent among women who were compliant with supplement use and had high bone lead levels (patella bone lead ≥5 &mgr;g/gm bone). Among this subgroup, supplement use was associated with an estimated reduction in mean blood lead of 1.16 ug/dL (95% confidence interval = −2.08 to −0.23), an overall reduction of 16.4%.Conclusions.Among lactating women with relatively high lead burden, calcium supplementation was associated with a modest reduction in blood lead levels.

ISSN:1044-3983    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

Background.Support for the validity of food frequency questionnaires (FFQ) in preschool children using parental report is limited.Methods.We obtained dietary information for 68 children age 1–3 years using three or four 24-hour recalls and a FFQ regarding the child’s diet covering one year from families in Denver, CO from 1997 to 1999. FFQs were completed by the parents, and recalls were collected via interviews with the parents and alternate caregivers, where applicable. Nutrient biomarkers were measured in the plasma of 38 of the children. All nutrients were adjusted for energy intake using residuals, and log-transformed where necessary.Results.Correlations (Pearson r) between the FFQ and the average of the recalls were 0.33 for protein, 0.41 for carbohydrate, 0.39 for fat, 0.42 for vitamin C, 0.27 for alpha-tocopherol, and 0.08 for total energy intake. We found no substantial changes in these correlations after stratification by whether or not meals and snacks were provided by caregivers other than the parents. The highest correlations (Spearman r) with biological measures were 0.51 between plasma ascorbic acid and FFQ vitamin C, and 0.48 between plasma and FFQ alpha-tocopherol.Conclusions.The FFQ shows mostly good agreements with multiple 24-hour recalls and biomarkers in preschool children. In addition, the validity of the FFQ using parental report does not appear to be compromised when there are meal providers in addition to the parents.

ISSN:1044-3983    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

Background.Previous studies have found that infants born at night and during weekends and holidays have an increased risk of perinatal mortality. However, these associations may be confounded by the distribution of high-risk deliveries according to time of birth.Methods.We undertook a population-based cohort study of 694,888 singleton births without elective cesarean section in Sweden between 1991 and 1997. We estimated relative risks of intrapartum and early neonatal death according to the hour, day and month of delivery. Estimated risk ratios were adjusted for gestational age, birth weight for gestational age, malformations, induction of labor, breech presentations and year of birth.Results.Infants of high-risk deliveries were more often delivered during daytime (8:00 am to 7:59 pm). Compared with infants born during daytime, infants born at night were at increased risk of early neonatal death (adjusted risk ratio = 1.28; 95% confidence interval = 1.13–1.46), but not intrapartum death (1.05; 0.71–1.54). If this association is causal, 12% of early neonatal deaths can be attributed to the increased risk among nighttime births. There was no association of weekend or holiday births with risks of intrapartum or early neonatal death.Conclusions.Infants born at night may be at increased risk of early neonatal death.

ISSN:1044-3983    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

Background.Blood pressure, particularly pulse pressure, is associated with arterial wall stiffness, but little is known about its relation to stiffness of other parts of the body. We examined the extent to which blood pressure levels in young healthy children are related to stiffness of various tissues.Methods.In November 2000, we studied 95 healthy prepubertal children (41 boys and 54 girls, within age range 8–10 years) from two primary schools in the city of Zeist, The Netherlands. Systolic and diastolic blood pressure and pulse pressure were analyzed in relation to various tissue indicators of stiffness, including active joint mobility and skin extensibility. All results were adjusted for age, sex, body height, body weight and muscle strength as possible confounders.Results.Diastolic blood pressure was lower with increased active joint mobility (multivariate generalized linear regression coefficient = −4.5 mmHg per standard deviation [SD] joint mobility; 95% confidence interval [CI] = −7.8 to −1.2). Pulse pressure was lower with increased skin extensibility (−3.2 mmHg per SD skin extensibility; CI = −5.2 to −1.1), through a higher diastolic blood pressure (2.0 mmHg per SD skin extensibility; CI = 0.2–3.9) and possibly lower systolic blood pressure (−0.8 mmHg per SD skin extensibility; CI = −3.5 to 1.9). These associations were mutually independent. Additional adjustment for reported musculoskeletal problems or physical activity levels did not materially change the findings.Conclusions.Our findings support the hypothesis that constitutional stiffness of body tissues may be associated with blood pressure levels and eventually cardiovascular risk.

ISSN:1044-3983    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

Background.As part of a multicenter study relating traffic-related air pollution with incidence of asthma in three birth cohort studies (TRAPCA), we used a measurement and modelling procedure to estimate long-term average exposure to traffic-related particulate air pollution in communities throughout the Netherlands; in Munich, Germany; and in Stockholm County, Sweden.Methods.In each of the three locations, 40–42 measurement sites were selected to represent rural, urban background and urban traffic locations. At each site and fine particles and filter absorbance (a marker for diesel exhaust particles) were measured for four 2-week periods distributed over approximately 1-year periods between February 1999 and July 2000. We used these measurements to calculate annual average concentrations after adjustment for temporal variation. Traffic-related variables (eg, population density and traffic intensity) were collected using Geographic Information Systems and used in regression models predicting annual average concentrations. From these models we estimated ambient air concentrations at the home addresses of the cohort members.Results.Regression models using traffic-related variables explained 73%, 56% and 50% of the variability in annual average fine particle concentrations for the Netherlands, Munich and Stockholm County, respectively. For filter absorbance, the regression models explained 81%, 67% and 66% of the variability in the annual average concentrations. Cross-validation to estimate the model prediction errors indicated root mean squared errors of 1.1–1.6 &mgr;g/m3for PM2.5and 0.22–0.31 *10−5m−1for absorbance.Conclusions.A substantial fraction of the variability in annual average concentrations for all locations was explained by traffic-related variables. This approach can be used to estimate individual exposures for epidemiologic studies and offers advantages over alternative techniques relying on surrogate variables or traditional approaches that utilize ambient monitoring data alone.

ISSN:1044-3983    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

Background.Two recent studies estimated that users of nonsteroidal antiinflammatory drugs (NSAIDs) have a two-fold increase in risk of hospitalization for congestive heart failure and that this effect is larger among patients with preexisting cardiovascular diseases.Methods.To evaluate the association between NSAID use and the risk of first-diagnosed episode of heart failure, we conducted a case-control study nested in a population-based cohort of individuals 40–84 years of age and registered in the U.K. General Practice Research Database at 1 January 1996. We excluded patients with a diagnosis of heart failure or cancer before that time and followed source members until a first-time recorded diagnosis of heart failure or cancer, or until 31 December 1996 if no disease occurred. The analysis included 857 confirmed cases and 5000 controls frequency-matched to cases by age (interval of 1 year) and sex.Results.The estimated adjusted relative risk of heart failure associated with prescription of NSAIDs was 1.6 (95% confidence interval = 1.2–2.1). The relative risk was greater during the first month of therapy and was independent of treatment indication. The relative risk was 1.9 (1.3–2.8) among patients with prior history of hypertension, diabetes or renal failure and 1.3 (0.9–1.9) among individuals without these conditions.Conclusions.Initiation of NSAID therapy may double the risk of developing heart failure in susceptible individuals. Patients with renal failure, diabetes or hypertension when taking NSAIDs might be at a greater risk of developing heart failure than patients without those conditions.

ISSN:1044-3983    

出版商:OVID    

年代:2003

数据来源: OVID