Biomedical subjects

C Peretz

Publications and source records attributed to C Peretz.

16 recordsLinked to original sources

PubMed2006

Quadriceps and hamstring isokinetic strength and electromyographic activity measured at different ranges of motion: a reproducibility study.

Isokinetic strength measurements of the quadriceps and hamstring that are commonly conducted using a 90 degrees range of motion (RoM) may involve some risk to specific knee patient groups. Testing these muscles at a much shorter RoM may reduce the risk but in order to render this method clinically acceptable the reproducibility of the derived test findings has to be established. Therefore the main objective of this study was to assess the reproducibility of isokinetic peak torque and normalized EMG scores of these muscles based on 90 degrees (0-90 degrees flexion, LR) and three successive short RoMs: 0-30 degrees (SR1), 30-60 degrees (SR2) and 60-90 degrees (SR3). Eight healthy subjects were tested three times with a 2 week between-session interval. All tests were performed on the dominant limb and consisted of maximal concentric and eccentric exertions. The velocities applied were 90 degrees /s for LR and 30 degrees /s for each of the SRs. Findings indicated no between-session improvement in strength. Based on the coefficient of variation the measurement error for all isokinetic strength scores remained stable throughout the testing sessions ranging 0.6-13.9% with the absolute majority of instances less than 10%. The reproducibility of the EMG scores was poorer ranging 1.5-25% and 0.5-19% for the quadriceps and hamstring, respectively. It is concluded that testing of knee muscles at short (30 degrees ) RoMs does not compromise the reproducibility of the strength or EMG scores derived from the commonly used RoM of 90 degrees . However, whereas strength was reproducible to within the accepted clinical standards, the corresponding EMG scores were characterized by a wider error band.

Adult↗

PubMed2005

Falls in outpatients with Parkinson's disease: frequency, impact and identifying factors.

Falls are one of the most serious complications of gait disturbances in patients with Parkinson's disease (PD). Among previous reports, the percentage of patients with PD who fall varies between 38% to 68%. We sought to determine the frequency of falls and the factors associated with falls in a group of patients with idiopathic PD who attended an outpatient, tertiary movement disorders clinic. 350 ambulatory, non-demented patients (230 males) were studied. Mean age was 69.7+/-10.6 years (range: 43-97 yrs) and mean duration of PD symptoms was 8.6+/- 6.2 years (range: 1-33 yrs). Assessments included characterization of demographics, disease duration, disease severity as measured by the Hoehn and Yahr Scale (H&Y), co-morbidities, the presence of depressive symptoms, the presence of urinary incontinence, use of anti-parkinsonian medications, and two performance-based tests of balance and gait (tandem standing and Timed Up & Go). Fall history was determined during three time periods: previous week, previous month, and previous year. Univariate and multivariate logistic regression models were applied to evaluate the relationship between the above-mentioned factors and falls. 46% of the subjects reported at least one fall in the previous year and 33% reported 2 or more falls and were classified as Fallers. Fallers had significantly more prolonged and advanced PD compared with Non-fallers (p=0.001 and p<0.001, respectively). Urinary incontinence was the factor most closely associated with falls (crude and adjusted OR were 1.95 and 5.89, respectively). Other factors significantly associated with fall status included increased Timed Up & Go times and increased PD duration. These findings confirm that falls are a common problem among patients with advanced PD and suggest easily measurable features that may be used to prospectively identify those PD patients with the greatest risk of falls.

Accidental Falls↗

PubMed2004

Antiparkinsonian medication is not a risk factor for the development of hallucinations in Parkinson's disease.

BACKGROUND: It was commonly assumed that psychotic phenomena in Parkinson's disease (PD) are mainly drug related. Accumulating evidence suggests the existence of other risk factors for psychosis in PD. Aims. To evaluate the contribution of the drug profile of patients with PD to emergence of hallucinations. METHODS: We compared patients with and without hallucinations, using Cox proportional hazards model, concerning drug profile at the time of hallucinations emergence. RESULTS: Of 422 consecutive patients, 113 had dementia, while 90 patients experienced hallucinations (46 had both dementia and hallucinations). The mean levodopa dose for the group of patients with hallucinations was 650 +/- 279 mg/day at the time of hallucinations onset, which was not significantly different from the levodopa dose at last visit for the group without hallucinations (621 +/- 326 mg/day). Supplementary treatment with amantadine, selegiline, dopamine agonists, entacapone and anticholinergics did not increase the risk for the development of hallucinations. CONCLUSIONS: We did not confirm drug treatment as a risk factor for hallucinations in PD. Our study suggests the existence of "endogenic" factors as substantial contributors in the genesis of PD hallucinations. The clinical implications may be earlier administration of antipsychotic treatment and not as traditionally accepted, dose reduction of antiparkinsonian drugs.

Adult↗

PubMed2004

Hand rhythmic tapping and timing in Parkinson's disease.

BACKGROUND: Dysrhythmia is one of the features frequently associated with the motor disturbance in Parkinson's disease (PD). The mechanism responsible for this phenomenon is not known. OBJECTIVES: To assess the rhythmic movements of the hand in PD patients in general and in parkinsonian subtypes. METHODS: Fifty-one PD patients (32 males) with mean age 66.3 +/- 9.1 years (6.6 years of symptoms) and 36 healthy controls (age 64.9 +/- 13.2, range 40-85) were studied. Subjects were asked to tap with their dominant or less affected arm on a digitized switch board at their most comfortable pace (16 s), fastest tapping speed (12 s), and at different frequencies provided by a metronome. The mean rhythm and the tap-to-tap variation were compared. Performance of the PD patients and control subjects were compared, as there were different subtypes of PD patients. Patients were subclassified into: tremor predominant (TP) (14 patients), freezing predominant (FP) (11 patients), akinetic-rigid (AR) (12 patients) and an unclassified group (UC) (14 patients). Results. There was no significance difference between patients and controls in the self-chosen, most comfortable tapping rate or in the tap-to-tap variation of the self-paced task. PD patients tapped at a significantly slower rate than controls when asked to tap at their fastest rate (4.39 +/- 1.32 vs. 5.14 +/- 1.31 Hz; p < 0.01). This difference was the result of an especially slow performance of the TP and AR subgroups (3.85+/-1.20 and 3.88+/-1.46, respectively; p < 0.01 compared to the control group). TP was the only subgroup to show an increased tap-to-tap variation at their fastest tapping rate compared to the control group (0.070 +/- 0.057 vs. 0.029 +/- 0.025 s, respectively, p < 0.05). The TP subgroup also showed hastening when they followed an externally given rhythm of 2.5 Hz and they tapped at 2.73 +/- 0.36 Hz p < 0.05). CONCLUSIONS: Externally driven and self-paced tapping are preserved in patients with PD, when examined at their best 'on' state. The tremor predominant subgroup seems to have specific pacing disturbances.

Adult↗

PubMed2002

Application of mixed-effects models for exposure assessment.

The benefits of using linear mixed-effects models for occupational exposure assessment were studied by re-analysing three data sets from two published surveys with repeated exposure measurements. The relative contributions of particular characteristics affecting exposure levels were assessed as in a multiple regression model, while controlling for the correlation between repeated measurements. While one-way ANOVA allows one only to estimate unconditioned variance components, a mixed model enables estimation of between- and within-worker variance components of exposure levels while accounting for the fixed effects of work characteristics. Consequently, we can identify the work characteristics affecting each variance component. Mixed models were applied to the data sets with repeated measurements and auxil iary information on work characteristics. The between-worker variance components were reduced by 35, 66 and 80%, respectively, in the three data sets when work characteristics were taken into account. The within-worker (day-to-day) variability was reduced only in the pig farmer data set, by 25%, when accounting for work activities. In addition, coefficients of work characteristics from the mixed model were compared with coefficients resulting from originally published multiple linear regression models. In the rubber manufacturing data, the coefficients of the mixed model showed similar relative importance, but were generally smaller than the coefficients from regression models. However, in the pig farm data, only the coefficients of work activities were somewhat reduced. The mixed model is a helpful tool for estimating factors affecting exposure and suitable variance components. Identifying the factors in the working environment that affect the between-worker variability facilitates a posteriori grouping of workers into more uniformly exposed groups. Identifying the factors that affect the within-worker variance is helpful for hazard control and in designing efficient sampling schemes with reference to time schedule.

Analysis of Variance↗

PubMed2002

Upper airway inflammation and respiratory symptoms in domestic waste collectors.

OBJECTIVES: To compare respiratory symptoms and upper airway inflammation in domestic waste collectors and controls, and to find the association between measures of upper airway inflammation on the one hand and exposure concentrations of organic dust or respiratory symptoms on the other hand. METHODS: In a cross sectional study among 47 waste collectors and 15 controls, questionnaire data on respiratory symptoms were collected. Nasal lavage (NAL), to assess upper airway inflammation, was performed before and after a work shift at the beginning and at the end of the working week. In NAL fluid, cells were counted and differentiated and concentrations of interleukin 6 (IL6), IL8, tumour necrosis factor-alpha (TNF alpha), and IL1 beta were measured. In collectors, inhalable dust samples were collected in which bacterial endotoxin and mould beta(1-->3)-glucan were assessed. RESULTS: Prevalence of respiratory symptoms was higher in waste collectors than in controls. Geometric mean exposure concentrations were 0.58 mg/m(3) for dust, 39 EU/m(3) for endotoxin, and 1.3 microg/m(3) for beta(1-->3)-glucan. At the end of the week collectors had higher concentrations of total cells and IL8 in NAL before and after a shift than controls (cells, before 1.9-fold p<0.10, after 3.3-fold p<0.01; IL8, before and after 1.8-fold p<0.05), and after/before work shift ratios of total cells were also higher (2.3-fold p=0.06) in collectors than in controls. Cells in NAL fluid consisted predominantly of neutrophils and epithelial cells, whereas eosinophils and mononuclear cells were rarely found. Exposure to dust and endotoxin was associated with concentrations of IL8 after the shift (p<0.05). Increased concentrations of IL8 (p<0.05) and total cells (p<0.10) after the shift were associated with respiratory symptoms. Concentrations of IL6, TNF alpha, and IL1 beta were not associated with waste collecting, symptoms, or exposure. CONCLUSIONS: Waste collectors show signs of increased upper airway inflammation and respiratory symptoms compared with controls. Exposure to organic dust probably underlies the inflammation mediated by neutrophils that result in respiratory symptoms.

Adult↗

PubMed2001

Maximal versus feigned active cervical motion in healthy patients: the coefficient of variation as an indicator for sincerity of effort.

STUDY DESIGN: Maximal and submaximal (feigned) cervical motions in healthy patients were compared. OBJECTIVE: To test the efficiency of the coefficient of variation in differentiating maximal (sincere) from submaximal (feigned) cervical motion in healthy patients. SUMMARY OF BACKGROUND DATA: Although limitation of cervical motion is a recognized impairment, no well-founded approach for verifying the degree to which a patient is maximizing his or her performance is available currently. METHODS: A new ultrasound-based system for three-dimensional motion analysis of the head was used to test 25 healthy patients (22 women and 3 men) ages 26 to 48 years. During the first test, (Test 1), the patients were asked initially to move the head maximally at a self-determined velocity in all the primary directions: flexion, extension, right and left rotation, and right and left lateral flexion. They then were presented with a short vignette describing a fictitious accident and asked, using the same protocol, to perform the same types of cervical motions as if they had experienced an injury. No further instructions were provided. A retest (Test 2) in reverse order (feigned effort first) took place 1 to 16 weeks (mean, 3.3 weeks) later. RESULTS: The range of motion and average velocity were significantly smaller (P = 0.0001) in the feigned than in the maximal performance in all directions and on both tests. Feigned range of motion and velocity also were significantly reduced in Test 2 (P = 0.006), as compared with those in Test 1 (P = 0.0001). The range of motion coefficient of variation in the feigned performance (CVf) remained stable on the retest, but was significantly larger on both tests (P < 0.001) than the corresponding CV derived from maximal performance (CVm). Furthermore, a case-by-case analysis showed that whereas the American Medical Association guidelines identified only 16% of the feigned cases, the use of CVf and CVm resulted in a corresponding rate of 87%. Tolerance intervals at 95% and 99% indicated total separation between the distributions of CVf and CVm, respectively. The average velocity-based CVf and CVm were not of a comparable differentiating power. CONCLUSIONS: This study indicates that in healthy patients, feigned performance may be differentiated from maximal (sincere) performance effectively and reproducibly using the coefficient of variation.

Adult↗

PubMed1999

Workers' right-to-know legislation: does it work?

Workers' right-to-know (WRTK) laws and regulations were established to empower workers to protect their health by providing them with information about the hazards to which they are exposed while at work. The present study was conducted to examine the implementation of WRTK regulations in Israel. We interviewed 552 workers and 33 safety officers from a random sample employed at 50 industrial plants. The workers' questionnaire included items on awareness and self-management of workplace hazards, and the safety officers answered questions about job experience and hazards communications to workers. In 36% of cases workers and their safety officers disagreed about the existence of hazards in the workplace (p < 0.001). Most (78%) of the workers' knowledge about work hazards was based on informal sources, i.e., not those stipulated by the regulations. There were also discrepancies between worker and safety officer reports regarding the provision of safety training upon employment (p < 0.001), recent instructions about special risks and distribution of relevant printed material. We found that more than 5% of workers were unable to read the language in which the hazards material was written and 22% had levels of education below that required to comprehend the technical terms used. There are serious problems in the implementation of WRTK regulations in Israel. We recommend that employers be made aware of the importance of these laws and of their proactive duty to comply with them and that the material distributed to workers be written in simpler terms and/or explained orally in a language they understand. These findings have important implications for all countries with similar legislation and should form the basis for further and more comprehensive studies world-wide.

Adolescent↗

PubMed1997

The variability of exposure over time: a prospective longitudinal study.

Four hundred and forty personal air measurements were carried out on 54 workers, employed in the main processes in six different factories (6-13 in each). Potential exposure was to lead, benzene and dust. Ten randomly repeated hygiene surveys were carried out over 1 year. In order to estimate the magnitude of the variability in workers' exposure over time, its sources, the variance between workers and the variance within a worker, a nested unbalanced analysis-of-variance model was fitted to the log-transformed data. Of the total exposure variance, the within variance of a worker's exposure over time was 51% (geometrical standard deviation, GSD = 3.1) and the between workers, factories and air contaminants variance was 49%. The exposure variance between all the workers was due mainly to variance between workers within the same factory (67%). Outdoor locations, mobility of the worker and mobility of the sources of exposure result in a positive influence on both the variance between (26%, ANOVA) and the variance of a worker over time (39%, regression). These variables are therefore important in the sampling strategy of workers' exposure. For valid compliance testing and assessment of workers' exposure the mean and the within- and between-variance of the workers' exposure over time should be considered. The exposure should be measured several times a year randomly in order to prevent workers misclassification. To assess yearly exposure, a GSD = 3.1 can be used to calculate confidence limits for the arithmetic mean of worker's exposure measurements, in circumstances similar to those in this study.

Air Pollution↗

PubMed1995

Determination of consumer satisfaction: a basic step for quality improvement of an occupational hygiene service.

In order to define priorities for improvement of the Occupational Hygiene Service, Institute for Occupational Health, Tel Aviv University, consumer satisfaction was evaluated by postal questionnaire. The questionnaire covered items on service accessibility and quality, including staff courtesy and respect for the consumer, cost, satisfaction with the service in general over time, and satisfaction with the last service received, and was sent to all 144 regular clients of the institute during the years 1990 and 1991. Satisfaction items were rated from 1 (not at all satisfied) to 5 (completely satisfied). Multivariant analysis showed that: (i) satisfaction with the waiting period for the last service report and satisfaction with the courtesy of the last service and respect for the consumer had the strongest influence on general satisfaction with the service over time; (ii) satisfaction with the waiting period for the last service report was also the most important component in satisfaction with the last service received. Despite the increasing interest in Israel in health service costs, and because the price of the service is subsidized (50%), this item was not found to be significant with regard to satisfaction with the service. In conclusion, we recommend the use of this relatively easy and inexpensive methodology which allowed us to define precisely the key factor for service improvement, ie the waiting period for the service report.

Consumer Behavior↗

PubMed1995

The effectiveness of regulations requiring periodic occupational hygiene monitoring.

The passing of regulations requiring periodic occupational hygiene monitoring surveys is one way of controlling workers' exposure to hazardous materials. The results of this study showed that this control is ineffective. The source of data was Occupational Hygiene Survey (OHS) records which were archived in the Institute for Occupational Health, Tel Aviv University and related only to workplaces that requested an OHS. The mean frequency of surveys carried out in the workplaces studied was significantly lower than the required one. Although the main factors required to ensure effective implementation of the regulations exist in Israel, i.e., monitoring services and enforcement authorities, excursions above permitted levels (overexposure) are still widely occurring. From all the measurements made over the study period (1989-1991) the ranges of overexposure were 31-75% for silica, 26-32% for talc, and 19-41% for lead. The results of the study highlighted the need to strengthen the authority of the bodies involved in occupational hygiene by increasing intervention. This could be achieved by enlarging the capabilities of the enforcement authorities by giving authority to occupational health physicians and to the organization carrying out the survey.

Environmental Monitoring↗

PubMed1992

Assessment of the extent of implementation of the recommendations made in occupational hygiene survey reports.

The extent of implementation of recommendations contained in field reports from the Occupational Hygiene Unit of the Institute for Occupational Health at the Tel Aviv University, was investigated. The results show that 33% were not carried out at all and 16% were only partially carried out. A number of factors influenced the extent of implementation, in particular the degree of involvement of the management in worker health and welfare, an active safety system in operation, the professional skill and seniority of the person in charge of safety, awareness by the workers of health and safety matters, the existence of a specific budget for health and safety and a regulatory system concerning occupational exposure.

Health Knowledge, Attitudes, Practice↗

PubMedDate not supplied

Improved non-negative estimation of variance components for exposure assessment.

Hygiene surveys of pollutants exposure data can be analyzed by analysis of variance (ANOVA) model with a random worker effect. Typically, workers are classified into homogeneous exposure groups, so it is very common to obtain a zero or negative ANOVA estimate of the between-worker variance (sigma2B). Negative estimates are not sensible and also pose problems for estimating the probability (theta) that in a job group, a randomly selected worker's mean exposure exceeds the occupational exposure standard. Therefore, it was suggested by Rappaport et al. to replace a non-positive estimate with an approximate one-sided 60% upper confidence bound. This article develops an alternative estimator, based on the upper tolerance interval suggested by Wang and Iyer. We compared the performance of the two methods using real data and simulations with respect to estimating both the between-worker variance and the probability of overexposure in balanced designs. We found that the method of Rappaport et al. has three main disadvantages: (i) the estimated sigma2B remains negative for some data sets; (ii) the estimator performs poorly in estimating sigma2B and theta with two repeated measures per worker and when true sigma2B is quite small, which are quite common situations when studying exposure; (iii) the estimator can be extremely sensitive to small changes in the data. Our alternative estimator offers a solution to these problems.

Bias↗

PubMedDate not supplied

Exposure to benzene in fuel distribution installations: monitoring and prevention.

The authors used a mixed-effects model on a cohort of 258 randomly chosen workers in 7 fuel-distribution facilities to examine the association between airborne benzene exposure and task and timing factors. During an 8-y period, 692 repeated personal measurements were performed. Filler task, warm month, Tuesday, credit day, and time period (1992-1996) were associated significantly with higher exposures to benzene. The authors controlled for the time period, and task type strongly affected the between-worker variance; therefore, two exposure groups (i.e., fillers and nonfillers) were adequate for purposes of exposure grouping strategy. Timing factors (after controlling for task and period effects) strongly affected the high within-worker variance (> 2 than between-worker variance). Long-term exposure would be better represented if the sample was stratified by warm/nonwarm months and if measurement days were selected randomly.

Adult↗

PubMedDate not supplied

Serum immunoglobulins in chronic lymphocytic leukemia.

Serum immunoglobulin levels were periodically determined in 70 CLL patients and the changes were correlated with several clinical and laboratory parameters. It was found that the IgG and IgA levels decreased significantly as the disease progressed. A low IgG concentration was found at the time of diagnosis in 18.7% and after six years in about 50% of the patients. The IgM concentration, although initially low, increased during the follow-up in 43% of the patients and in four of them a monoclonal fraction appeared in the serum. The changes in the immunoglobulins did not correlate with age, sex or initial leukocyte count. Stage O patients as well as untreated patients also had a decrease in their immunoglobulin levels but advanced disease stage and especially continuous chemotherapy seemed to augment the drop in the immunoglobulin levels. Neither the initial immunoglobulin levels nor the subsequent changes, absolute or relative, had a significant prognostic value.

Agammaglobulinemia↗

PubMedDate not supplied

Responses of occupational physicians and laboratory staff to reports of high blood lead levels.

We evaluated the responses of physicians specializing in occupational health and of laboratory personnel engaged in occupational lead monitoring when periodic blood lead analysis results exceeded the Biological Exposure Index (BEI). Legally, Israeli workers must be removed from the site of occupational lead exposure after a repeat test shows "value above BEI" (VABEI). The maximum legal period between a report of VABEI and the repeat test is 14 days. Physicians have the discretion to remove workers after the first VABEI test if deemed necessary. In 1987-88, 242 of 3,776 analyses had a VABEI, 167 of which were periodic tests. The average laboratory response time between receipt of the sample and VABEI reports to occupational physicians was 13 days (SE = 0.4). Medical records of 100 workers who had 134 tests with a VABEI were available. In 35 (26.1%) of these events the physicians recommended removing the workers from the exposure source, in 55 (41.0%) events the physicians required repeat tests, and in 44 (32.9%) they neither recommended removal nor repeated the tests. The minimum time lapse between the first and repeat test was 20 days. The second test yielded 24 VABEI. Physicians recommended removing workers from the source only in 13 (54.2%) of these cases. This study suggests that the system must be improved in order to ensure the proper response to VABEI results.

Attitude of Health Personnel↗