Bellamy, SL, Gibberd, R, Hancock, L, Howley, P, Kennedy, B, Klar, N, Lipsitz, S & Ryan, L 2000, 'Analysis of dichotomous outcome data for community intervention studies', STATISTICAL METHODS IN MEDICAL RESEARCH, vol. 9, no. 2, pp. 135-159.
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Community intervention trials are becoming increasingly popular as a tool for evaluating the effectiveness of health education and intervention strategies. Typically, units such as households, schools, towns, counties, are randomized to receive either intervention or control, then outcomes are measured on individuals within each of the units of randomization. It is well recognized that the design and analysis of such studies must account for the clustering of subjects within the units of randomization. Furthermore, there are usually both subject level and cluster level covariates that must be considered in the modelling process. While suitable methods are available for continuous outcomes, data analysis is more complicated when dichotomous outcomes are measured on each subject. This paper will compare and contrast several of the available methods that can be applied in such settings, including random effects models, generalized estimating equations and methods based on the calculation of 'design effects', as implemented in the computer package SUDAAN. For completeness, the paper will also compare these methods of analysis with more simplistic approaches based on the summary statistics. All the methods will be applied to a case study based on adolescent anti-smoking intervention in Australia. The paper concludes with some general discussion and recommendations for routine design and analysis.
Brown, KG, Kuo, TL, Guo, HR, Ryan, LM & Abernathy, CO 2000, 'Sensitivity analysis of US EPA's estimates of skin cancer risk from inorganic arsenic in drinking water', HUMAN AND ECOLOGICAL RISK ASSESSMENT, vol. 6, no. 6, pp. 1055-1074.
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The current U.S. Environmental Protection Agency's (USEPA's) risk analysis on the Integrated Risk Information System (IRIS) for arsenic in drinking water is based on an epidemiological study of skill cancer in Taiwan. Assumptions used in the USEPA applic
Brumback, BA 2000, 'A meta-analysis of case-control and cohort studies with interval-censored exposure data: application to chorionic villus sampling', Biostatistics, vol. 1, no. 2, pp. 203-217.
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Brumback, BA, Ryan, LM, Schwartz, JD, Neas, LM, Stark, PC & Burge, HA 2000, 'Transitional regression models, with application to environmental time series', JOURNAL OF THE AMERICAN STATISTICAL ASSOCIATION, vol. 95, no. 449, pp. 16-27.
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Environmental epidemiologists often encounter time series data in the form of discrete or other nonnormal outcomes; for example, in modeling the relationship between air pollution and hospital admissions or mortality rates. We present a case study examining the association between pollen counts and meteorologic covariates. Although such time series data are inadequately described by standard methods for Gaussian time series, they are often autocorrelated, and warrant an analysis beyond those provided by ordinary generalized linear models (GLMs). Transitional regression models (TRMs), signifying nonlinear regression models expressed in terms of conditional means and variances given past observations, provide a unifying framework for two mainstream approaches to extending the GLM for autocorrelated data. The first approach models current outcomes with a GLM that incorporates past outcomes as covariates, whereas the second models individual outcomes with marginal GLMs and then couples the error terms with an autoregressive covariance matrix. Although the two approaches coincide for the Gaussian GLM, which serves as a helpful introductory example, in general they yield fundamentally different models. We analyze the pollen study using TRM's of both types and present parameter estimates together with asymptotic and bootstrap standard errors. In several cases we find evidence of residual autocorrelation; however, when we relax the TRM to allow for a nonparametric smooth trend, the autocorrelation disappears. This kind of trade-off between autocorrelation and flexibility is to be expected, and has a natural interpretation in terms of the covariance function for a nonparametric smoother. We provide an algorithm for fitting these flexible TRM's that is relatively easy to program with the generalized additive model software in S-PLUS. © 2000 Taylor and Francis Group, LLC.
Callipo, A, Cucchiara, R & Piccardi, M 2000, 'Computational models for image processing for shared-memory multiprocessors', Integrated Computer-Aided Engineering, vol. 7, no. 1, pp. 39-52.
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Different tasks in image processing exhibit different computational requirements that should be considered with respect to the architecture. This is particularly critical in parallel machines where many parallelization techniques, as data partitioning an
Carlin, JB, Ryan, LM, Harvey, EA & Holmes, LB 2000, 'Anticonvulsant teratogenesis 4: Inter-rater agreement in assessing minor physical features related to anticonvulsant therapy', TERATOLOGY, vol. 62, no. 6, pp. 406-412.
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Background: We report on inter-rater agreement in the assessment of newborn infants with respect to a range of minor physical features in a cohort study of the fetal effects of maternal anticonvulsant use during pregnancy. Methods: Infants from three groups (exposed to anticonvulsants, seizure history but no medication exposure, and unexposed controls) were examined by both a pediatrician/teratologist, who was blinded with respect to the mother's exposure status, and an unblinded research assistant. Agreement on assessments for selected anomalies associated with anticonvulsant therapy was measured by kappa-statistics, as well as by more sensitive log-linear modeling techniques, which allow examination of possible covariate effects on the strength of agreement. Although the physician and research assistant agreed on a high proportion of cases (80-90%), kappa values were modest (0.2-0.5), partly because of the low prevalence of the anomalies considered. To explore how agreement varies within subgroups, we used recently developed methods for studying agreement based on log-linear models. Results: Log-linear modeling indicated that there was substantial variation in pattern of agreement between different individual research assistants but that other factors (e.g., exposure category, sex, and birthweight) did not appear to be related to agreement. Our results suggest that research assistants with more experience showed the highest degree of agreement with the physicians. Conclusions: Our results have implications for both clinical practice and epidemiologic research and underline the importance of thorough training of staff in the definitions to be used and also the need for multiple independent assessments of these subtle anomalies. (C) 2000 Wiley-Liss, Inc.
Chen, D, Cho, SI, Chen, CZ, Wang, XO, Damokosh, AI, Ryan, L, Smith, TJ, Christiani, DC & Xu, XP 2000, 'Exposure to benzene, occupational stress, and reduced birth weight', OCCUPATIONAL AND ENVIRONMENTAL MEDICINE, vol. 57, no. 10, pp. 661-667.
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Objectives - The association between birth weight and exposure to benzene, work stress, and other occupational and environmental hazards was investigated. Methods - In a large petrochemical industry, 792 pregnant workers were enrolled and followed up through delivery between May 1996 and December 1998. Exposure to benzene and other solvents was assessed by an industrial hygienist based on each woman's job title and workplace information. Other occupational and environmental exposures and personal information, including perceived work stress, exposure to noise, physical exertion at work, and passive smoking, were obtained by an interview questionnaire. Univariate and multivariate recession models were used to examine the individual and combined associations of occupational and environmental exposures with birth weight, with adjusment for major confounders including gestational age. Results - In the univariate model, birth weight was negatively associated with exposure to benzene (-58 g (95% confidence interval (95% CI), -115 to -2)) and with work stress (-84 g (95% CI, -158 to -10)). In the multivariate model, there was a significant interaction between exposure to benzene and work stress relative to reduced birth weight, after adjustment for other environmental and occupational exposures and personal variabless. Adjusted mean birth weight was 3445 g (95% CI 3401 to 3489) among those with neither exposure, 3430 g for those with exposure to benzene only, 3426 g for those with work stress only, and 3262 g (95% CI 3156 to 3369) for those with both exposures. In order words, there was 183 g (95% CI 65 to 301) reduction in birth weight among those with both exposure to benzene and work stress compared with those with neither exposure. Other work or environmental factors could not explain these findings. Conclusions - Low level exposure to benzene and work stress interact to reduce birth weight in this population.
Chen, KLB, Gertig, D, Ryan, L, Willett, W, Christiani, D & Hunter, D 2000, 'Toenail arsenic levels and squamous cell carcinoma of the skin', EPIDEMIOLOGY, vol. 11, no. 4, pp. S58-S58.
Cho, SI, Chen, C, Chen, D, Damokosh, AI, Yiu, L, Ryan, L, Smith, TJ, Lasley, BL, O'Connor, JF, Wang, L, Wilcox, AJ, Christiani, DC & Xu, X 2000, 'Benzene exposure and time to conception.', AMERICAN JOURNAL OF EPIDEMIOLOGY, vol. 151, no. 11, pp. S13-S13.
Cho, SI, Goldman, MB, Ryan, L, Chen, C, Damokosh, AI, Christiani, DC, Lasley, BL, O'Connor, JF, Wilcox, AJ & Xu, X 2000, 'Reliability of HCG data interpretation.', AMERICAN JOURNAL OF EPIDEMIOLOGY, vol. 151, no. 11, pp. S48-S48.
Clayton, D, Campbell, MJ, Longford, NT, Armstrong, B, Richardson, S, Rushton, L, Raab, GM, Quinn, M, Nelder, JA, Bland, M, Macfarlane, A, Dryden, IL, Smith, RI, Berhane, K, Thomas, DC, Cotton, JW, Coull, BA, Mezzetti, M, Ryan, LM, Cowles, K, Cox, C, Cox, LH, Gupta, S, Hosmane, BS, Gurrin, LC, Pettitt, AN, Saez, M, Sheppard, L & Lumley, T 2000, 'Combining evidence on air pollution and daily mortality from the 20 largest US cities: a hierarchical modelling strategy - Discussion', JOURNAL OF THE ROYAL STATISTICAL SOCIETY SERIES A-STATISTICS IN SOCIETY, vol. 163, pp. 284-302.
Contreras, M & Ryan, LM 2000, 'Fitting nonlinear and constrained generalized estimating equations with optimization software', BIOMETRICS, vol. 56, no. 4, pp. 1268-1271.
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In this article, we present an estimation approach for solving nonlinear constrained generalized estimating equations that can be implemented using object-oriented software for nonlinear programming, such as nlminb in Splus or fmincon and Isqnonlin in Matlab. We show how standard estimating equation theory includes this method as a special case so that our estimates, when unconstrained, will remain consistent and asymptotically normal. To illustrate this method, we fit a nonlinear dose-response model with nonnegative mixed bound constraints to clustered binary data from a developmental toxicity study. Satisfactory confidence intervals are found using a nonparametric bootstrap method when a common correlation coefficient is assumed for all the dose groups and for some of the dose-specific groups.
Cucchiara, R, Grana, C, Piccardi, M & Prati, A 2000, 'Statistic and knowledge-based moving object detection in traffic scenes', ITSC2000. 2000 IEEE Intelligent Transportation Systems. Proceedings (Cat. No.00TH8493), pp. 27-32.
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Cucchiara, R, Piccardi, M & Mello, P 2000, 'Image analysis and rule-based reasoning for a traffic monitoring system', IEEE Transactions on Intelligent Transportation Systems, vol. 1, no. 2, pp. 119-130.
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The paper presents an approach for detecting vehicles in urban traffic scenes by means of rule-based reasoning on visual data. The strength of the approach is its formal separation between the low-level image processing modules (used for extracting visual data under various illumination conditions) and the high-level module, which provides a general-purpose knowledge-based framework for tracking vehicles in the scene. The image-processing modules extract visual data from the scene by spatio-temporal analysis during daytime, and by morphological analysis of headlights at night. The high-level module is designed as a forward chaining production rule system, working on symbolic data, i.e., vehicles and their attributes (area, pattern, direction, and others) and exploiting a set of heuristic rules tuned to urban traffic conditions. The synergy between the artificial intelligence techniques of the high-level and the low-level image analysis techniques provides the system with flexibility and robustness.
Cucchiara, R, Piccardi, M & Prati, A 2000, 'Hardware prefetching techniques for cache memories in multimedia applications', Proceedings Fifth IEEE International Workshop on Computer Architectures for Machine Perception, pp. 311-319.
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Declerck, L, Molenberghs, G, Aerts, M & Ryan, L 2000, 'Litter-based methods in developmental toxicity risk assessment', ENVIRONMENTAL AND ECOLOGICAL STATISTICS, vol. 7, no. 1, pp. 57-76.
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Developmental toxicity experiments are designed to assess potential adverse effects of drugs and other exposures on developing fetuses from pregnant dams. Extrapolation to humans is a very difficult problem. An important issue here is whether risk assessment should be based on the fetus or the litter level. In this paper, fetus and litter-based risks that properly account for cluster size are defined and compared for the beta-binomial model and a conditional model for clustered binary data. It is shown how the hierarchical structure of non-viable implants and viable but malformed offspring can be incorporated. Risks based on a joint model for death/resorption and malformation are contrasted with risks based on an adverse event defined as either death/resorption or malformation. The estimation of safe exposure levels for all risk types is discussed and it is shown how estimation of the cluster size distribution affects variance estimation. The methods are applied to data collected under the National Toxicology Program and in large sample simulations.
Gabrys, B & Bargiela, A 2000, 'General fuzzy min-max neural network for clustering and classification', IEEE Transactions on Neural Networks, vol. 11, no. 3, pp. 769-783.
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Geys, H, Molenberghs, G, Declerck, L & Ryan, L 2000, 'Flexible quantitative risk assessment for developmental toxicity based on fractional polynomial predictors', BIOMETRICAL JOURNAL, vol. 42, no. 3, pp. 279-302.
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Risk assessment for developmental toxicity studies in rodents is faced with the fairly involved data structure of clustered multivariate binary outcomes. While likelihood methods for this setting do not abound, we show that a conditional model, combined with pseudo-likelihood inference and fractional polynomial predictor functions, as proposed by ROYSTON and ALTMAN (1994), are a promising way forward. The methods are illustrated using teratology data collected under the National Toxicology Program.
Goetghebeur, E & Ryan, L 2000, 'Semiparametric regression analysis of interval-censored data', BIOMETRICS, vol. 56, no. 4, pp. 1139-1144.
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We propose a semiparametric approach to the proportional hazards regression analysis of interval-censored data. An EM algorithm based on an approximate likelihood leads to an M-step that involves maximizing a standard Cox partial likelihood to estimate regression coefficients and then using the Breslow estimator for the unknown baseline hazards. The E-step takes a particularly simple form because all incomplete data appear as linear terms in the complete-data log likelihood. The algorithm of Turnbull (1976, Journal of the Royal Statistical Society, Series B 38, 290-295) is used to determine times at which the hazard can take positive mass. We found multiple imputation to yield an easily computed variance estimate that appears to be more reliable than asymptotic methods with small to moderately sized data sets. In the right-censored survival setting, the approach reduces to the standard Cox proportional hazards analysis, while the algorithm reduces to the one suggested by Clayton and Cuzick (1985, Applied Statistics 34, 148-156). The method is illustrated on data from the breast cancer cosmetics trial, previously analyzed by Finkelstein (1986, Biometrics 42, 845-854) and several subsequent authors.
Harris, JE, Ryan, L, Hoover, HC, Stuart, RK, Oken, MM, Benson, AB, Mansour, E, Haller, DG, Manola, J & Hanna, MG 2000, 'Adjuvant Active Specific Immunotherapy for Stage II and III Colon Cancer With an Autologous Tumor Cell Vaccine: Eastern Cooperative Oncology Group Study E5283', Journal of Clinical Oncology, vol. 18, no. 1, pp. 148-148.
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PURPOSE: A randomized phase III clinical trial of adjuvant active specific immunotherapy (ASI) with an autologous tumor cell–bacillus Calmette-Guérin (BCG) vaccine was conducted to determine whether surgical resection plus ASI was more beneficial than resection alone in stage II and III colon cancer patients. PATIENTS AND METHODS: Patients (n = 412) with colon cancer (297 with stage II disease, 115 with stage III disease) were randomly allocated to an observation arm or to a treatment arm in which they received three weekly intradermal vaccine injections of 107 irradiated autologous tumor cells beginning approximately 4 weeks after surgery. The first two weekly injections also contained 107 BCG organisms. Patients were observed for determination of time to recurrence and disease-free and overall survival. RESULTS: This was a negative study in that after a 7.6-year median follow-up period, there were no statistically significant differences in clinical outcomes between the treatment arms. However, there were disease-free survival (P = .078) and overall survival (P = .12) trends in favor of ASI when treatment compliance was evaluated, ie, patients who received the intended treatment had a delayed cutaneous hypersensitivity (DCH) response to the third vaccination (induration ≥5 mm). Also, the magnitude of the DCH response correlated with improved prognosis. The 5-year survival proportion was 84.6% for those with indurations greater than 10 mm, compared with 45.0% for those with indurations less than 5 mm. CONCLUSIONS: When all randomized patients were evaluated, no significant clinical benefit was seen with ASI in surgically resected colon cancer patients with stage II or III colon cancer. However, there was an indication that treatment compliance with effective immunization results in disease-free and overall survival benefits.
Holmes, LB, Rosenberger, PB, Harvey, EA, Khoshbin, S & Ryan, L 2000, 'Intelligence and physical features of children of women with epilepsy', TERATOLOGY, vol. 61, no. 3, pp. 196-202.
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The teratogenicity of maternal epilepsy has been attributed to several factors, including the antiepileptic drugs taken to prevent seizures during pregnancy, the occurrence of seizures during pregnancy, and the factors in the mother that caused her to have epilepsy. We have addressed the hypothesis that the children of women who have a history of epilepsy (seizure history), but who took no antiepileptic drugs (AED) and had no tonic-clonic seizures in pregnancy, have an increased risk of malformations and diminished intelligence. The frequency of cognitive dysfunction was determined in 57 seizure history and 57 matched control children aged 6-16 years. The masked evaluation of the children included a physical and neurologic examination and testing with the Wechsler Intelligence Scale for Children-Revised (WISC-R) and a systematic physical examination for the features of the fetal AED syndrome. The evaluation of both parents of each child included a test of reasoning (Ravens Progressive Matrix) and a physical examination. There were no differences between the two groups of children in either IQ scores or physical features; none of the seizure history children was judged to have the 'anticonvulsant face' or digit hypoplasia. This study had 80% power to rule out a difference of seven or more IQ points between the two groups, based on a two-sided test at a 5% level of significance. Our confidence in concluding that there was no difference between seizure history and control infants was strengthened by the fact that no statistically significant differences were observed with respect to multiple outcomes, including eight related measures of intelligence. Thirty (53%) of the seizure history mothers resumed taking AED after the birth of the child we evaluated. Additional studies are needed to address the teratogenicity of the antiepileptic drugs as monotherapy. (C) 2000 Wiley-Liss, Inc.
Ibrahim, JG, Chen, MH & Ryan, LM 2000, 'Bayesian variable selection for time series count data', STATISTICA SINICA, vol. 10, no. 3, pp. 971-987.
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We consider a parametric model for time series of counts by constructing a likelihood-based generalization of a model considered by Zeger (1988). We consider a Bayesian approach and propose a class of informative prior distributions for the model paramet
Levy, JI, Houseman, EA, Ryan, L, Richardson, D & Spengler, JD 2000, 'Particle concentrations in urban microenvironments', ENVIRONMENTAL HEALTH PERSPECTIVES, vol. 108, no. 11, pp. 1051-1057.
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Although ambient particulate matter has been associated with a range of health outcomes, the health risks for individuals depend in part on their daily activities. Information about particle mass concentrations and size distributions in indoor and outdoor microenvironments can help identify high-risk individuals and the significant contributors to personal exposure. To address these issues in an urban setting, we measured particle count concentrations in four size ranges and particulate matter ≤ 10 μm (PM10) concentrations outdoors and in seven indoor microenvironments in Boston, Massachusetts. Particle counts and PM10 concentrations were continuously measured with two light-scattering devices. Because of the autocorrelation between sequential measurements, we used linear mixed effects models with an AR-1 autoregressive correlation structure to evaluate whether differences between microenvironments were statistically significant. In general, larger particles were elevated in the vicinity of significant human activity, and smaller particles were elevated in the vicinity of combustion sources, with indoor PM10 concentrations significantly higher than the outdoors on buses and trolleys. Statistical models demonstrated significant variability among some indoor microenvironments, with greater variability for smaller particles. These findings imply that personal exposures can depend on activity patterns and that microenvironmental concentration information can improve the accuracy of personal exposure estimation.
Li, J, Dong, G & Ramamohanarao, K 2000, 'Making Use of the Most Expressive Jumping Emerging Patterns for Classification', Knowledge Discovery And Data Mining, Proceedings: Current Issues And New Applications, vol. 1805, no. NA, pp. 220-232.
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Classification aims to discover a model from training data that can be used to predict the class of test instances. In this paper, we propose the use of jumping emerging patterns (JEPs) as the basis for a new classifier called them JEP-Classifier. Each J
Li, Y, Zhang, C & Swan, JR 2000, 'An information filtering model on the Web and its application in JobAgent', Knowledge-Based Systems, vol. 13, no. 5, pp. 285-296.
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Lu, MCK, Sammel, MD, Cleveland, RH, Ryan, LM & Holmes, LB 2000, 'Digit effects produced by prenatal exposure to antiepileptic drugs', TERATOLOGY, vol. 61, no. 4, pp. 277-283.
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The hypothesis tested was that digit anomalies among individuals exposed in utero to antiepileptic drugs (AED) are best identified by a systematic search, including radiographs and dermatoglyphics, rather than relying only on visual inspection. A systematic search was made for five types of digit abnormalities in 46 AED-exposed individuals ages 5-29 years in comparison with controls: visible anomalies, size of fingernails, dermal ridge patterns, length of metacarpals and phalanges, and qualitative changes in the distal phalanges. Among the AED-exposed, nail size was not decreased. However, there was a 10.8% frequency of digit anomalies, a 12% frequency of three or more arch patterns, and significant shortening and qualitative changes in the distal phalanges, all of which are consistent with the fetal effects of AED. Among the 42 individuals who underwent all evaluations, 14.3% had two or more of these abnormalities, most of which would not be identified by clinical inspection. This frequency is much higher in these AED-exposed individuals than in the general population. Radiographs in 13 individuals over a period of several years showed that the changes in the phalanges and metacarpals persisted. (C) 2000 Wiley-Liss, Inc.
Ryan, LM 2000, 'Statistical issues in toxicology', JOURNAL OF THE AMERICAN STATISTICAL ASSOCIATION, vol. 95, no. 449, pp. 304-308.
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Ryan, LM 2000, 'Statistical Issues in Toxicology', Journal of the American Statistical Association, vol. 95, no. 449, pp. 304-304.
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Sanchez, JM, Collia, F, Stoler, JM, McGuirk, C, Holmes, LB, Ryan, L & Lieberman, E 2000, 'Letter to the editor (multiple letters)', Genetics in Medicine, vol. 2, no. 5, pp. 300-301.
Stoler, JM, McGuirk, C, Holmes, LB, Ryan, L & Lieberman, E 2000, 'Untitled - Response', GENETICS IN MEDICINE, vol. 2, no. 5, pp. 300-301.
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Thurston, SW, Ryan, L, Christiani, DC, Snow, R, Carlson, J, You, LY, Cui, SC, Ma, GH, Wang, LH & Huang, YM 2000, 'Petrochemical exposure and menstrual disturbances', AMERICAN JOURNAL OF INDUSTRIAL MEDICINE, vol. 38, no. 5, pp. 555-564.
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Background: An exploratory, cross-sectional retrospective study was conducted to examine the effects of benzene exposure on menstrual problems. Methods: The study was based on a survey administered to over 3,000 women who worked in a large petrochemical company in Beijing, China. An abnormal menstrual cycle length (AMCL), defined as an average menstrual cycle length of greater than 35 days or less than 21 days, is the major outcome of interest. Results: After 7 years of benzene exposure, the adjusted odds ratio of having AMCL for each additional 5 years of exposure was 1.71 (95% CI 1.27-2.31). Feeling stressed at work was also an important predictor. Conclusions: This study suggests a significant association of benzene exposure and perceived stress with menstrual disturbance. A prospective study is needed to confirm this finding. (C) 2000 Wiley-Liss, Inc.
Tierney, J, Alvegård, TA, Sigurdsson, H, Antman, K, Bacchi, M, Baker, LH, Benjamin, RS, Brady, MF, Bramwell, V, Bui, BN, Edmonson, JH, Fletcher, CDM, Gherlinzoni, F, Jones, G, Patel, M, Leyvraz, S, Mosseri, V, Omura, GA, Parmar, MKB, Stewart, LA, Tierney, JF, Rouëssé, J, Ruiz de Elvira, MC, Ryan, L, Souhami, RL, Sylvester, R, Tursz, T, van Oosterom, AT & Yang, JC 2000, 'Adjuvant chemotherapy for localised resectable soft tissue sarcoma in adults', Cochrane Database of Systematic Reviews, vol. 2015, no. 2.
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Background: Individually, randomised trials have not shown conclusively whether adjuvant chemotherapy benefits adult patients with localised resectable soft-tissue sarcoma. Objectives: Adjuvant chemotherapy aims to lessen the recurrence of cancer after surgery with or without radiotherapy. The objective of this review was to assess the effects of adjuvant chemotherapy in adults with resectable soft tissue sarcoma after such local treatment. Search methods: We searched the Cochrane Controlled Trials Register, UKCCCR Register of Cancer Trials, Physicians Data Query, EMBASE, MEDLINE and CancerLit. Selection criteria: Randomised trials of adjuvant chemotherapy after local treatment in adults with localised resectable soft tissue sarcoma were included. Only trials in which accrual was completed by December 1992 were included. Data collection and analysis: Individual patient data were obtained. Accuracy of data and quality of randomisation and follow-up of trials was assessed. Main results: Fourteen trials of doxorubicin-based adjuvant chemotherapy involving 1568 patients were included. Median follow-up was 9.4 years. For local recurrence-free interval the hazard ratio (HR) with chemotherapy was 0.73 (95% Confidence Interval (CI) 0.56 to 0.94). For distant recurrence-free interval it was 0.70 (95% CI 0.57 to 0.85). For overall recurrence-free survival it was 0.75 (95% CI 0.64 to 0.87). These correspond to significant absolute benefits of 6 to 10% at 10 years. For overall survival (OS) the HR of 0.89 (95% CI 0.76 to 1.03) was not significant but potentially represents an absolute benefit of 4% (95% CI 1 to 9) at 10 years. There was no consistent evidence of a difference in effect according to age, sex, stage, site, grade, histology, extent of resection, tumour size or exposure to radiotherapy. However, the strongest evidence of a beneficial effect on survival was shown in patients with sarcoma of the extremities. Authors' conclusions: Doxorubicin-based adjuvant chemothe...
Wang, XB, Chen, DF, Niu, TH, Wang, ZX, Wang, LH, Ryan, L, Smith, T, Christiani, DC, Zuckerman, B & Xu, XP 2000, 'Genetic susceptibility to benzene and shortened gestation: Evidence of gene-environment interaction', AMERICAN JOURNAL OF EPIDEMIOLOGY, vol. 152, no. 8, pp. 693-700.
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This study investigated whether the association between low level benzene exposure and shortened gestation is modified by two susceptibility genes, CYP1A1 and GSTT1. This report includes 542 (302 nonexposed, 240 benzene-exposed) nonsmoking and nondrinking mothers of singleton live births at Beijing Yanshan Petrochemical Corporation between June 1995 and June 1997. Epidemiologic and clinical data and blood samples were obtained from mothers. Multiple linear regression models were used to estimate the associations of benzene exposure and genetic susceptibility with gestational age, adjusting for maternal age, education, parity, stress, passive smoking, prepregnancy weight and height, and infant's sex. Without consideration of genotype, benzene exposure was associated with a decrease in mean gestational age of 0.29 (standard error (SE), 0.12) week. When stratified by the maternal CYP1A1 genotype, the estimated decrease was 0.54 (SE, 0.12) week for the AA group, which was significantly greater (p = 0.003) than that for the Aa/aa group, which showed no decrease in gestational age. When both CYP1A1 and GSTT1 were considered, the greatest decrease was found among exposed mothers with the CYP1A1 AA-GSTT1 absent group (0.79 (SE, 0.25) week) and the CYP1A1 AA-GSTT1 present group (0.50 (SE, 0.22) week). Among the nonexposed, genetic susceptibility alone did not confer a significant adverse effect. This study provides evidence of gene-environment interaction and supports further assessment of the role of genetic susceptibility in the evaluation of reproductive toxins.
Warram, JH, Scott, LJ, Hanna, LS, Wantman, M, Cohen, SE, Laffel, LMB, Ryan, L & Krolewski, AS 2000, 'Progression of microalbuminuria to proteinuria in type 1 diabetes - Nonlinear relationship with hyperglycemia', DIABETES, vol. 49, no. 1, pp. 94-100.
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Zanobetti, A 2000, 'Generalized additive distributed lag models: quantifying mortality displacement', Biostatistics, vol. 1, no. 3, pp. 279-292.
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There are a number of applied settings where a response is measured repeatedly over time, and the impact of a stimulus at one time is distributed over several subsequent response measures. In the motivating application the stimulus is an air pollutant such as airborne particulate matter and the response is mortality. However, several other variables (e.g. daily temperature) impact the response in a possibly non-linear fashion. To quantify the effect of the stimulus in the presence of covariate data we combine two established regression techniques: generalized additive models and distributed lag models. Generalized additive models extend multiple linear regression by allowing for continuous covariates to be modeled as smooth, but otherwise unspecified, functions. Distributed lag models aim to relate the outcome variable to lagged values of a time-dependent predictor in a parsimonious fashion. The resultant, which we call generalized additive distributed lag models, are seen to effectively quantify the so-called 'mortality displacement effect' in environmental epidemiology, as illustrated through air pollution/mortality data from Milan, Italy.
Zanobetti, A, Wand, M, Schwartz, J & Ryan, L 2000, 'Mortality displacement in Milan, Italy.', EPIDEMIOLOGY, vol. 11, no. 4, pp. S77-S77.
Zhang, J, Arnold, JF & Frater, MR 2000, 'A cell-loss concealment technique for MPEG-2 coded video', IEEE Transactions on Circuits and Systems for Video Technology, vol. 10, no. 4, pp. 659-665.
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Audio-visual and other multimedia services are seen as important sources of traffic for future telecommunication networks, including wireless networks. A major drawback with some wireless networks is that they introduce a significant number of transmissi