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PubMed1995

Magnetic field exposure among utility workers.

The Electric and Magnetic Field Measurement Project for Utilities--the Electric Power Research Institute (EPRI) Electric and Magnetic Field Digital Exposure (EMDEX) Project (the EPRI EMDEX Project)--was a multifaceted project that entailed technology transfer, measurement protocol design, data management, and exposure assessment analyses. This paper addresses one specific objective of the project: the collection, analysis, and documentation of power-frequency magnetic field exposures for a diverse population of utility workers. Field exposure data measured by an EMDEX system were collected by volunteer utility employees at 59 sites in four countries between September, 1988, and September, 1989. Specially designed sampling procedures and data collection protocols were used to ensure uniform implementation across sites. Volunteers within 13 job classifications recorded which of eight work or three nonwork environments they occupied while wearing an EMDEX meter. Approximately 50,000 hours of magnetic field exposure records taken at 10 s intervals were obtained, about 70% of which were from work environments. Exposures and time spent in environments were analyzed by primary work environment, by occupied environment, and by job classification. Generally, for utility-specific job classifications related to the generation, transmission, and distribution of electricity, the field and exposure measurements in terms of workday mean field were higher than in more general occupations. The job classifications with the highest (median workday mean) exposure were substation operators (0.7 microT) and electricians (0.5 microT). Total variance also tended to be largest for utility-specific job classifications. For these workers, the contributions of between-worker and within-worker variances to total variance were about the same. Measurements in utility-specific environments were higher than in more general environments. Estimates of time-integrated exposure indicated that utility-specific job classifications received about one-half or more of their total exposure on the job. The nonwork field and exposure distributions for workers in all job categories were comparable with median nonworkday means of about 0.09 microT.

Documentation↗

PubMed2002

Physical exercise and immune system function in cancer survivors: a comprehensive review and future directions.

BACKGROUND: There are a limited number of interventions for cancer survivors following completion of primary therapy that might reduce the risk of cancer recurrence and/or secondary malignancies and increase survival times. It has been proposed that physical exercise may be beneficial by enhancing the anticancer immune system response. The purpose of the current article is to: 1) briefly describe the immune system response to tumors, 2) discuss the impact of anticancer therapy on immune system function in cancer survivors, 3) provide a systematic and comprehensive review of the extant literature examining physical exercise and immune system function in cancer survivors, and 4) offer a critical analysis of this literature and outline directions for future research. METHODS: A comprehensive literature search up to March 2001 identified empirical articles that examined the effects of physical exercise training on immune system function in cancer survivors from CD-ROM database searches and manual searches. RESULTS: To the authors' knowledge, six empirical studies published between 1994 and 2000 have examined physical exercise and immune system function in cancer survivors. Overall, four out of six studies reported statistically significant improvements in a number of cancer-related immune system components as a result of exercise. However, there are several limitations that must be considered when interpreting the findings of these studies. These limitations involve the samples, designs, physical exercise interventions, physical fitness assessments, and immunologic assessments. CONCLUSIONS: Additional research is needed to determine if physical exercise in cancer survivors may reduce the risk of cancer recurrence and secondary malignancies and increase survival times.

Adult↗

PubMed2002

Report from a workshop on multianalyte microsphere assays.

Multiplexed assays using fluorescent microspheres is an exciting technique that has been gaining popularity among researchers, particularly those in the public health field. Part of its popularity is due to its flexibility, as both immunoassays and oligonucleotide hybridization assays can be developed on this platform. This report summarizes a workshop held by the Centers for Disease Control and Prevention that discussed issues surrounding these assays and the Luminex 100 xMAP instrument. Topics included instrumentation, assay design, sample matrix and volume, quality control, and development of commercial applications.

Animals↗

PubMed2003

Limits of fine-mapping a quantitative trait.

Once a significant linkage is found, an important goal is reducing the error in the estimated location of the linked locus. A common approach to reducing location error, called fine-mapping, is the genotyping of additional markers in the linked region to increase the genetic information. The utility of fine-mapping for quantitative trait linkage analysis is largely unknown. To explore this issue, we performed a fine-mapping simulation in which the region containing a significant linkage at a 10-centiMorgan (cM) resolution was fine-mapped at 2, 1, and 0.5 cM. We simulated six quantitative trait models in which the proportion of variation due to the quantitative trait locus (QTL) ranged from 0.20-0.90. We used four sampling designs that were all combinations of 100 and 200 families of sizes 5 and 7. Variance components linkage analysis (Genehunter) was performed until 1,000 replicates were found with a maximum lodscore greater than 3.0. For each of these 1,000 replications, we repeated the linkage analysis three times: once for each of the fine-map resolutions. For the most realistic model, reduction in the average location error ranged from 3-15% for 2-cM fine-mapping and from 3-18% for 1-cM fine-mapping, depending on the number of families and family size. Fine-mapping at 0.5 cM did not differ from the 1-cM results. Thus, if the QTL accounts for a small proportion of the variation, as is the case for realistic traits, fine-mapping has little value.

Chromosome Mapping↗

PubMed2002

A unified framework for transmission-disequilibrium test analysis of discrete and continuous traits.

This paper presents a unified framework for transmission-disequilibrium tests for discrete and continuous traits. A conditional score test is derived that maximizes power to detect small effects for any exponential family distribution, which includes binary and normal distributions, and distributions that are skewed or have non-normal kurtosis. The specific distributional form need not be specified, and the method applies to sibships of arbitrary size. Formulas for the distribution of the test statistic are given for models including complex genetic effects (additive, dominant, and recessive gene action), covariates, multiple gene models including gene-gene interactions or heterogeneity, and gene-environment interactions. We develop refinements of our method for trait-based sampling designs and multiple siblings that can have dramatic effects on power.

Alleles↗

PubMed1995

Biracial differences in physical activity and body composition among women.

Overweight among black females is almost two times as frequent as among white females. Genetics, caloric intake, and physical activity have been identified as possible explanatory factors. This study assessed the differences in physical activity and body composition in 76 white and 66 black adult females. Black women had significantly higher (p = .0001) percent body fat (32.2 +/- 7.1) than white women (27.7 +/- 6.5) with a similar difference in weight (4.4 kg) approaching significance (p = .055). Physical activity was assessed using a structured 24-hour recall instrument. A purposive sampling design was implemented to control for age, education and occupation. A summary physical activity value unit for the 24-hour period revealed a significantly greater mean value for white females (41.93 +/- 4.7) than for black females (40.01 +/- 3.9) suggesting white females were more physically active (p = .02) although this was not a function of biracial differences in play/recreation and exercise/sport type of activities. Although both black and white females were found to be sedentary (MET value < or = 2) over 90 percent of the time, black women are significantly more sedentary (p = .03). Biracial differences in discretionary non-exercise oriented activities may contribute to different rates of overweight observed between black and white women.

Adult↗

PubMed2005

Gentamicin-loaded bone cement with clindamycin or fusidic acid added: biofilm formation and antibiotic release.

The formation of staphylococcal biofilms on experimental bone cements, loaded with 0.5 or 1.0 g of active gentamicin and an additional equivalent amount of gentamicin, clindamycin, or fusidic acid was investigated. The biofilms were formed in a modified Robbins device over a 3-day time span and the influence of the additional antibiotics was quantified by expressing the number of colony forming units relative to the corresponding bone cement containing only gentamicin. Combinations of gentamicin with either fusidic acid or clindamycin reduced growth of clinical isolates of both gentamicin-sensitive Staphylococcus aureus and gentamicin-resistant coagulase-negative staphylococci to approximately 28%. To determine whether adding a second antibiotic has influence on the gentamicin release, cement blocks were placed in phosphate buffer and aliquots were taken at designated sampling intervals. The influence of the additional antibiotics was quantified by expressing the percentage released of the total amount of antibiotic incorporated in the different bone cements. After 3 days, all bone cements had released similar percentages of gentamicin, whereas more clindamycin and fusidic acid were released after doubling their concentration in the bone cements. In conclusion, bone cements loaded with combinations of gentamicin and clindamycin or fusidic acid are more effective in preventing biofilm formation than bone cements with gentamicin as a single drug. In addition, the presence of clindamycin or fusidic acid in gentamicin-loaded bone cement has no influence on the total gentamicin release.

Biofilms↗

PubMed2000

Service inputs and costs of care related to outcomes among cognitively impaired nursing home residents.

BACKGROUND: There are over 17 000 nursing homes in the United States. Within these, special care units (SCUs) provide a separate residential and/or activity locus for residents, and are expected to provide more staff time and more specialized staff assignments. This paper addresses a fundamental issue relating to the nature, quality and quantity of resident care inputs: what impacts of SCUs are associated with added service inputs, and thus with personnel costs, recognizing that personnel account for the majority of costs associated with nursing home care? AIMS OF THE STUDY: The aim of this aspect of the study was to determine the extent to which additions of staff would result in a diminution of deviant behaviors among residents of special care and of traditional care units. METHOD: The data were collected from a random sample of ten downstate nursing homes located in New York State. Using rigorous sampling procedures, random samples of 40 residents were drawn from each of the facilities, equally divided between special care unit and traditional care unit residents. Thus, the sampling design involved two levels of clustering: subjects were clustered within units and units were clustered within facilities. The observational behaviour measure was taken from the INCARE (institutional version of the Comprehensive Assessment and Referral Evaluation). The behavioral observation measure contains 23 items such as "disruptive of others", "picks/pulls clothing", "repetitive movements", "repetitive questioning"and "wandering". Each item is rated as to frequency of occurrence; ratings are collected on three occasions, and averaged. Outcome and covariate data (e.g., behavior and cognition) were collected by trained research staff who visited each site for three to four weeks of intensive data collection, accomplished through direct resident interviews, staff interviews and questionnaires and chart data abstraction. The clinical staff time data were collected using the InfoAide system, whereby each care provider used a portable barcode scanner to record the type of care given, the recipient and the duration of care. A random effects model using the SAS mixed procedure was applied to the data; adhering to this model, some effects were fixed and some random. The random effects were comprised of the subject (intercept or subject starting point at baseline) and the unit; used here was restricted maximum likelihood (REML) with the EM algorithm. RESULTS: There was a significant reduction of behavior disorder associated with more provision of aide time in SCUs as contrasted with non-SCUs. The greater the service provided, the greater the slope, i.e., the greater the reduction. That is, while SCU residents showed improvements in behavior accompanying increases in aide time, no such change was observed among non-SCU residents. IMPLICATIONS FOR HEALTH CARE PROVISION AND USE: The significant effect of SCU + time + aide-minutes indicates that more aide time on SCUs was associated with improvement in behavior. It appears that the important ingredient in relation to the reduction of behavior disorder is not membership in an SCU per se, but the provision of more aide time within SCUs. Those SCUs that provide more aide time have a better behavior outcome. Thus, these findings point to additional paths for exploration, i.e., future research needs to focus on elements of SCUs such as the available amounts of program and staff resources rather than on SCU status alone.

Journal Article↗

PubMed2005

Forward telescoping bias in reported age of onset: an example from cigarette smoking.

Age at the onset of a disorder is one of its key descriptive characteristics. Early onset may indicate increased risk of a severe course and increased genetic liability. However, retrospectively reported onset in surveys is subject to forward telescoping, a bias in which respondents report events closer to the time of interview than is true. We examined the effect of this bias on age of onset for smoking initiation and daily smoking. Data came from the 1966-77 birth cohorts interviewed in the cross-sectional National Household Surveys on Drug Abuse (NHDSA) 1979-98 (N = 82,122). An association between age at onset and age at interview, within birth year, was found for experimenters and for daily smokers. This was indicative of forward telescoping. As age at interview increased from 12 to 25 the probability of reporting early onset dropped by half. An association was also found between early onset of daily smoking and age at interview. This response bias differed significantly by sex and race, created significant misclassification of smokers as late instead of early onset cases, and biased cohort comparisons from cross-sectional data. These results suggest efforts need to be made to limit the effect of forward telescoping in epidemiological studies by survey question and sampling design.

Adult↗

PubMed2004

Histamine2 receptor antagonist use and decline in cognitive function among community dwelling elderly.

PURPOSE: Previous studies have reported mixed results regarding the use of histamine(2) receptor antagonist use and cognitive function. This study evaluated the relationship between the use of histamine(2) receptor antagonists and cognitive decline among community dwelling elderly. METHODS: This cohort study included 2082 subjects from the Duke Established Populations for Epidemiologic Studies of the Elderly who were not cognitively impaired at baseline (1989/90). Histamine(2) receptor antagonist use was determined during in-home interviews. Cognitive function was assessed at 3 and 7 years after baseline by two measures: (1) incident cognitive impairment defined by the short portable mental status questionnaire (SPMSQ); and (2) cognitive decline (increase in two or more SPMSQ errors). Analyzes used multivariable discrete-time hazard models with weighted data adjusted for sampling design and controlled for demographic, health behavior characteristics and health status. RESULTS: At baseline, nearly 5% of participants used a histamine(2) receptor antagonist. During follow-up, incident cognitive impairment occurred in 24.0%, whereas 34.5% increased by two or more errors on the SPMSQ. In multivariable models, current histamine(2) receptor antagonist users compared to never users had a higher risk for cognitive impairment (Adj. RR 1.51; 95%CI 0.93-2.47) and for decline in performance (increase of two or more errors) on the SPMSQ (Adj. RR 1.24; 95%CI 0.74-2.08). A nonsignificant increased risk of cognitive impairment and decline with either higher dose or short-term use was found whereas a nonsignificant protective effect on cognitive decline with current long-term use was seen. CONCLUSIONS: These results suggest no beneficial effects, and perhaps a detrimental effect, of histamine(2) receptor antagonist use on cognitive function in community dwelling elderly.

Aged↗

PubMedDate not supplied

Genetic epidemiology: a review of the statistical basis.

Genetic epidemiology is the analysis of the familial distributions of traits, with a view to understanding any possible genetic basis; the fundamentals of this area are reviewed. The terminology of genetic models is fully described, since it is this wealth of terminology which can make it difficult for a statistician to enter the area. The statistical approaches to the analysis of data on sets of interrelated individuals are then discussed, and resulting problems of sampling design and analysis are considered.

Biometry↗

PubMedDate not supplied

A simulation study of three sequential methods for the comparison of two treatment groups when the response criterion is censored.

Three recent sequential methods, group sequential analysis (GSA), the sequential probability ratio test (SPRT) and the triangular test (TT) are well suited to randomized clinical trials with a censored response criterion, as they do not require matched pairs of patients. We undertook a simulation study to investigate their statistical properties and to compare these three methods with the fixed-sample design. Our results suggest that the three methods have the expected statistical properties for size and power; they allow an important reduction of the average number of events before stopping, except with GSA when there is no treatment difference; the triangular test (closed design) appears the optimal design, as the variance of the number of events is smaller than with the sequential probability ratio test (open design) and analysis after every twenty new events does not alter the statistical properties of these sequential methods and enhances their usefulness.

Biometry↗

PubMed1988

Genetic determination of the human EEG. Survey of recent results on twins reared together and apart.

In this article, we have discussed recent progress in quantifying the genetically determined component of the resting EEG. This progress has been made possible in particular by the application of advanced information processing techniques such as "supervised learning," and the development of a problem-oriented "similarity" concept. Our work aimed at modeling previous findings regarding the distinct individuality of human brain-wave patterns, the high similarity between the EEGs of monozygotic twins, and the average within-pair similarity of dizygotic twins. Thus, we had three objectives: First, we wanted to improve the quantification of EEG characteristics with respect to reproducibility and specificity by means of adaptive procedures and repeated measurements. Second, we wanted to compare the "typical" within-subject EEG similarity with the "typical" within-pair EEG similarity of monozygotic and dizygotic twins brought up together. Finally, we were interested in the degree to which environmental factors affect the characteristics of human brain-wave patterns. Our investigations were based on the empirical data derived from five different populations: (1) 81 healthy subjects, (2) 24 pairs of monozygotic twins brought up together, (3) 25 pairs of dizygotic twins brought up together, (4) 28 pairs of monozygotic twins reared apart, and (5) 21 pairs of dizygotic twins reared apart. Following our similarity conception, repeated measurements on the set of 81 individuals were used as design samples, and new registrations from the same individuals taken 14 days later were referred to as test samples in order to develop the appropriate method and to determine all required calibration parameters. This specific approach allowed us to construct EEG spectral patterns which, with a specificity and reproducibility of greater than 90% each, largely met the requirements of genetic EEG studies. Hence, we were able systematically to investigate the within-pair EEG similarity of our twin samples.(ABSTRACT TRUNCATED AT 400 WORDS)

Electroencephalography↗

PubMed1996

Landscape-Level Ecological Regions: Linking State-Level Ecoregion Frameworks with Stream Habitat Classifications

Regionalization is a form of spatial classification, where boundaries are drawn around areas that are relatively homogeneous in landscape characteristics. The process of delineating ecological regions, or ecoregions, includes the analysis of ecosystem structure. To date, ecoregions have been developed at national and state scales for research and resource management. Stream classification is another method to order the variability of aquatic habitats that spans spatial scales from microhabitat to valley segment. In this study, landscape-level ecoregions are developed for the upper Grande Ronde River basin in northeastern Oregon, 3000 sq km in area. The ecoregion framework presented here is proposed to bridge the gap between stream habitat and state-level ecoregion classifications. Classification at this scale is meant to address issues of management at local scales: to aid in sampling design, in extrapolation of the results of site-specific studies, and in the development of best management practices that are more predictive of ecosystem response than current methods.

Journal Article↗

PubMed1995

Measuring inhalant nitrite exposure in gay men: implications for elucidating the etiology of AIDS-related Kaposi's sarcoma.

We reviewed 12 epidemiologic studies conducted among gay men with AIDS to examine the role of potential 'cofactors' in the development of KS. Aspects of the studies reviewed include basic study design, wording of the questionnaires, and published results comparing KS patients with those who developed opportunistic infections indicative of AIDS. The studies included questions about sociodemographics, medical history, use of drugs, travel, and sexual behaviors. Patients were invited to provide blood and/or other specimens for laboratory analysis. The results of the review of epidemiologic studies are inconclusive. Nitrite inhalant use was a variable often associated with KS (five studies). The differences in outcomes of these studies may reflect differences in study designs, sample sizes, timing, quality, and content of interviews regarding nitrites, sexual behaviours and other potential cofactors. Epidemiologic study with careful consideration to content of questionnaires and laboratory testing may yet reveal the causes or cofactors for this tumor.

Acquired Immunodeficiency Syndrome↗

PubMed1995

A population survey of childhood accidents in Andalusia (Spain).

The aim of this study was to quantify the incidence of childhood accidents and to describe the morbidity profile of accidents in the autonomous region of Andalusia, Spain, for a three-month period (January to March) in 1990. For that purpose, a population survey based on a stratified multiphase sample design was carried out. We collected information about the most serious accident each child had suffered during the study period according to the opinion of the person interviewed (the mother in most of the cases). The cumulative incidence of childhood accidents in Andalusia for a three-month period was 19.4%, higher in urban areas than in rural ones, and lower as the age of the age group increased. As had occurred in previous studies, a higher number of accidents was observed among the male population, however, this result was not statistically significant. During the same period of time, the incidence of traffic accidents for population 0 to 14 years was 0.8%. Accidents among younger children (0 to 4 years of age) occurred mainly at home, while for children of a higher age (5 to 9 and 10 to 14) they took place, in a larger number of cases, either outdoors or at school. When the accident happened, those from the first group were mainly in the presence of their parents or other adults; in the other two groups, there were more friends or schoolmates present. Fractures and injuries, of minor severity, mainly on the head and the extremities and with no sequelae, were the most frequent types of accident.(ABSTRACT TRUNCATED AT 250 WORDS)

Accidents↗

PubMed1996

The dynamic household as a logical concept and its use in demography.

"The difficulties of applying conventional transition-based models to household change are discussed. More generally, what constitutes ¿time' and ¿change' is also considered. It is argued that many changes occurring within households such as leaving home are better-considered as ¿fuzzy' than crisp phenomena. An alternative perspective based on household change considered as an evolving network is proposed. The implications for sample designs which are designed to track explicit household dynamics (such as the Panel Study on Income Dynamics) are discussed. The ways in which particular forms of analysis come to dominate the scientific literature, including those for analysing household change are discussed in relation to non-linear dynamic models. Finally, it is argued that there would be considerable benefits if insights available from the physical, mathematical and biological sciences were to be more widely incorporated within technical demography." (SUMMARY IN FRE)

Demography↗

PubMed1994

Comparison of the Akaike Information Criterion, the Schwarz criterion and the F test as guides to model selection.

In pharmacokinetic data analysis, it is frequently necessary to select the number of exponential terms in a polyexponential expression used to describe the concentration-time relationship. The performance characteristics of several selection criteria, the Akaike Information Criterion (AIC), and the Schwarz Criterion (SC), and the F test (alpha = 0.05), were examined using Monte Carlo simulations. In particular, the ability of these criteria to select the correct model, to select a model allowing estimation of pharmacokinetic parameters with small bias and good precision, and to select a model allowing precise predictions of concentration was evaluated. To some extent interrelationships among these procedures is explainable. Results indicate that the F test tends to choose the simpler model more often than does either the AIC or SC, even when the more complex model is correct. Also, the F test is more sensitive to deficient sampling designs. Clearance estimates are generally very robust to the choice of the wrong model. Other pharmacokinetic parameters are more sensitive to model choice, particularly the apparent elimination rate constant. Prediction of concentrations is generally more precise when the correct model is chosen. The tendency for the F test (alpha = 0.05) to choose the simpler model must be considered relative to the objectives of the study.

Mathematics↗