616 results found
Jarup L, Arnold R, Grossinho A, et al., 2000, Health effects in populations living close to landfill sites, Publisher: LIPPINCOTT WILLIAMS & WILKINS, Pages: S88-S88, ISSN: 1044-3983
Stamler J, Appel L, Cooper R, et al., 2000, Dietary sodium chloride (salt), other dietary components and blood pressure: paradigm expansion, not paradigm shift., Acta Cardiol, Vol: 55, Pages: 73-78, ISSN: 0001-5385
Nieuwenhuijsen MJ, Toledano MB, Elliott P, 2000, Uptake of chlorination disinfection by-products; a review and a discussion of its implications for exposure assessment in epidemiological studies, Journal of Exposure Analysis and Environmental Epidemiology, Vol: 10, Pages: 586-599, ISSN: 1053-4245
We have reviewed the relevant issues in the exposure assessment of disinfection by-products (DBPs) of chlorination for epidemiological and health risk assessment. Various DBPs can be detected in drinking water and swimming pools, and the reported levels show a considerable range, but were generally below the current health standard for total trihalomethanes (TTHMs) (100 μg/l). Relatively little information is available on the correlation between the various DBPs in drinking water and in swimming pools. Chloroform was generally, but not always, the most predominant DBP. In epidemiological studies, TTHM levels have been used as an indicator for total DBP load, even though TTHM levels do not always correlate well with individual DPBs. Factors such as residence time, temperature, pH, organic content, including humic and fulvic acid and bromide levels affect the composition and levels of DBPs. Although there are biomarkers of DBPs, mainly for chloroform and more recently for the other volatile trihalomethanes (THMs) and the nonvolatile haloacetic acids (HAAs) such as trichloroacetic acid (TCAA) and dichloroacetic acid (DCAA), they have not been used in epidemiological studies. The THMs have been measured in exhaled breath and serum, while the HAAs have been measured in urine. These biomarkers have been useful to estimate the actual uptake of the DBPs and the relative contribution of various exposure routes. Physiologically based pharmacokinetic (PBPK) models exist for, e.g. chloroform, but their main target organs are the kidney and liver and they have not been used in epidemiological studies. Tap water ingestion, showering, bathing, swimming, boiling water and dishwashing are all activities that have been associated with the uptake of DBPs, and considerable variation in these activities has been observed between people. No studies have reported on the correlation between human uptake of DBPs and water - zone mean estimates, but various studies found a good correlatio
Ashmore MR, Batty K, Machin F, et al., 2000, Effects of traffic management and transport mode on the exposure of schoolchildren to carbon monoxide., Environmental Monitoring and Assessment, Pages: 49-57
Fischer P, Hoek G, van Reeuwijk H, et al., 2000, Traffic-related differences in outdoor and indoor concentrations of particles and volatile organic compounds in Amsterdam., Atmospheric Environment, Pages: 3713-3722
Melander A, Olsson J, Lindberg G, 1999, Increased mortality in type 2 diabetes patients using sulphonylurea and metformin in combination, DIABETOLOGIA, Vol: 42, Pages: A3-A3, ISSN: 0012-186X
Morton-Jones T, Diggle P, Elliott P, 1999, Investigation of excess environmental risk around putative sources: Stone's test with covariate adjustment, Statistics in Medicine, Vol: 18, Pages: 189-197, ISSN: 0277-6715
Stone proposed a method of testing for elevation of disease risk around a point source. Stone's test is appropriate to data consisting of counts of the numbers of cases, Y(i) say, in each of n regions which can be ordered in increasing distance from a point source. The test assumes that the Y(i) are mutually independent Poisson variates, with means μ(i) = E(i)λ(i), where the E(i) are the expected numbers of cases, for example based on appropriately standardized national incidence rates, and the λ(i) are relative risks. The null hypothesis that the λ(i) are constant is then tested against the alternative that they are monotone non-increasing with distance from the source. We propose an extension to Stone's test which allows for covariate adjustment via a log-linear model, μ(i) = E(i)λ(i)exp(Σ(j=1)(p) x(ij)β(j)), where the x(ij) are the values of each of p explanatory variables in each of the n regions, and the β(j) are unknown regression parameters. Our methods are illustrated using data on the incidence of stomach cancer near two municipal incinerators.
Dyer A, Elliott P, Chee D, et al., 1997, Urinary biochemical markers of dietary intake in the INTERSALT study., Pages: 1246S-1253S, ISSN: 0002-9165
The INTERSALT Study, an international, collaborative, cross-sectional investigation of the relation between blood pressure and dietary and other factors, used quality-controlled, standardized procedures and assessment of multiple possible confounding factors to study 10,079 men and women in 52 population-based samples in 32 countries. In this study 24-h urinary excretion data were used as biochemical markers of intakes of sodium, potassium, and protein, with repeat examinations done in a randomly selected 8% of participants to asses reliability and correct for regression-dilution bias. INTERSALT showed that high salt intake, low potassium intake, excess alcohol consumption, and energy imbalance resulting in overweight are critically involved in the origins of the high blood pressure prevalent among a majority of adult populations. The findings also show that obtaining accurate estimates of associations between dietary intake and blood pressure requires large population-based samples, high-quality dietary information, control for multiple confounding variables, and modern multivariate methods of data analyses, including correction of observed associations for within-person variation in intake.
Follmann D, Elliott P, Suh I, et al., 1992, Variance imputation for overviews of clinical trials with continuous response., J Clin Epidemiol, Vol: 45, Pages: 769-773, ISSN: 0895-4356
Overviews of clinical trials are an efficient and important means of summarizing information about a particular scientific area. When the outcome is a continuous variable, both treatment effect and variance estimates are required to construct a confidence interval for the overall treatment effect. Often, only partial information about the variance is provided in the publication of the clinical trial. This paper provides heuristic suggestions for variance imputation based on partial variance information. Both pretest-posttest (parallel groups) and crossover designs are considered. A key idea is to use separate sources of incomplete information to help choose a better variance estimate. The imputation suggestions are illustrated with a data set.
Stamler J, Rose G, Elliott P, et al., 1991, Findings of the International Cooperative INTERSALT Study., Hypertension, Vol: 17, Pages: I9-15, ISSN: 0194-911X
INTERSALT, an international cooperative study on electrolytes and other factors related to blood pressure, found, in within-population analyses involving 10,079 persons, a significant positive association between 24-hour urinary sodium excretion and systolic blood pressure and between the sodium/potassium ratio and systolic blood pressure. These significant findings were derived from analyses for individuals from all 52 centers and from the 48 centers remaining when persons from four low sodium centers were excluded. Potassium excretion of individuals was significantly and independently related inversely to their systolic blood pressure. For men and women, both separate and combined, the relation between sodium and systolic blood pressure was stronger for older than younger adults, perhaps reflecting the result of longer exposure with age or diminished capacity to handle a sodium load. Relations between electrolyte excretion and diastolic blood pressure in individuals were weaker than for systolic blood pressure. Body mass index and heavy alcohol consumption of individuals were strongly and independently related to blood pressure. In cross-population analyses with n = 52 or n = 48, sample median sodium excretion was significantly and independently related to the slope of systolic blood pressure and diastolic blood pressure with age. Other ecological analyses yielded inconsistent results. Four isolated populations showed low sodium excretion, low sodium/potassium excretion, low body mass index, and low alcohol consumption; sample median blood pressures were low, there was little or no upward slope of blood pressure with age, and high blood pressure was rare or nonexistent.
Elliott P, 1991, Observational studies of salt and blood pressure., Pages: I3-I8, ISSN: 0194-911X
The observational data relating salt and blood pressure (excluding INTERSALT) are reviewed. Important methodological difficulties and biases are inherent to both across- and within-population studies and confuse their interpretation. Across-population studies are positive but rely on data drawn from the international literature based on a variety of unstandardized field methods; they are prone to unmeasured (ecological) confounding. Within-population studies generally lack statistical power and are subject to major regression-dilution bias (because of considerable day-to-day variation in sodium intake), which could conceal true correlations between sodium and blood pressure. Nevertheless, an overview of reported studies that used 24-hour urine excretion to quantify intake shows positive and highly significant correlations between sodium and blood pressure for both men and women and for systolic and diastolic blood pressures. These results are consistent with the INTERSALT findings and those from trials of sodium restriction.
Elliott P, 1990, Small area health statistics in Europe, Information Services and Use, Vol: 10, Pages: 39-45, ISSN: 0167-5265
The use of routine health statistics in monitoring the health of populations in small areas is an important and exciting advance in environmental epidemiology. Requirements for a national system are discussed and illustrated with reference to the new Small Area Health Statistics Unit at the London School of Hygiene and Tropical Medicine. It is hoped that collaboration with groups in other countries holding similar data might be possible to extend and improve the methodology and also the power of small area based analyses. © 1990 Elsevier Science Publishers B.V.
Stamler J, Rose G, Stamler R, et al., 1989, INTERSALT study findings. Public health and medical care implications., Hypertension, Vol: 14, Pages: 570-577, ISSN: 0194-911X
INTERSALT found a significant association between 24-hour urine sodium excretion and systolic blood pressure in individuals. There was also a significant association between sodium and slope (increase) of blood pressure with age across population samples. The weight of evidence from animal-experimental, clinical, intervention, and epidemiological data favors a causal relation. INTERSALT data from 52 centers in 32 countries permit an estimate of effect on average population blood pressure of lower sodium intake. Based on the sodium-blood pressure association in individuals, it was estimated that a habitual population sodium intake that was lower by 100 mmol/day (e.g., 70 vs. 170 mmol/day) would correspond to an average population systolic pressure that was lower by at least 2.2 mm Hg. This size difference in systolic blood pressure in major US and UK population studies is associated with 4% lower risk of coronary death and 6% lower risk of stroke death in middle age. If habitual diet is both lower in sodium and higher in potassium with lower alcohol intake and less obesity, INTERSALT data estimate average population systolic pressure would be lower by 5 mm Hg. This was calculated to correspond to a 9% lower risk of coronary death and a 14% lower risk of stroke death. INTERSALT cross-population data also suggest that, with a 100 mmol/day lower sodium intake over the life span, the average increase in population systolic pressure from age 25 to 55 years would be less by 9 mm Hg, corresponding at age 55 to a 16% lower risk of subsequent coronary death and 23% lower risk of stroke death.(ABSTRACT TRUNCATED AT 250 WORDS)
CARVALHO JJM, BARUZZI RG, HOWARD PF, et al., 1989, BLOOD-PRESSURE IN 4 REMOTE POPULATIONS IN THE INTERSALT STUDY, HYPERTENSION, Vol: 14, Pages: 238-246, ISSN: 0194-911X
Marmot MG, Elliott P, 1989, Public health measures for blood pressure control in the whole community., Clin Exp Hypertens A, Vol: 11, Pages: 1171-1186, ISSN: 0730-0077
One approach to the prevention of blood pressure-associated cardiovascular disease is to find increased numbers of "hypertensives" and bring them under treatment. A complementary approach is to attempt to change the blood pressure distribution of the whole population. It can be calculated that, if the association between blood pressure level and mortality were reversible, a reduction of diastolic blood pressure of 5 mmHg in the population mean would be associated with a substantial reduction in cardiovascular mortality. The assumption of reversibility of risk of coronary heart disease may be more reasonable in the long than in the short term. The evidence from INTERSALT and other studies suggests that readily achievable changes in sodium and potassium intake, in body mass index and in alcohol intake, could lead to average blood pressure change across a whole population of 5 mmHg. A major task for public health is the implementation of such life-style changes among different social class and ethnic groups.
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