Brain frequency magnetic fields alter cardiac autonomic control mechanisms

OBJECTIVE

Heart rate variability (HRV) is a noninvasive indicator of sympathetic and vagal cardiovascular control known to be tightly correlated with sleep stages. Recent studies indicate that HRV in humans is altered by nocturnal exposure to power-frequency (60 Hz) magnetic fields. Given the central origin of autonomic cardiac control, we determined if field exposure in the beta(1) EEG/MEG frequency range was a more effective stimulus for HRV alteration than 60 Hz fields, and explored the mechanisms involved.

METHODS

Healthy young men were exposed (n=9) overnight to an intermittent magnetic field (16 Hz, 28.3 microTesla, microT), or sham exposed (n=9), under blind test conditions in a laboratory exposure facility.

RESULTS

Field exposure was associated (P<0.05) with reduced power in the low band of the HRV frequency spectrum, and with decreases in mean heart rate. Analysis of the timing of the R waves surrounding each on-off transition of the intermittent field revealed no evidence for a direct effect on the cardiac pacemaker.

CONCLUSIONS

Magnetic field exposure in the EEG/MEG beta(1) frequency range alters HRV via a CNS effect. Phase-resetting experiments rule out a direct effect on the cardiac pacemaker. Biophysical calculations of the intensity of the electric fields induced in brain versus heart under the present exposure conditions are also consistent with and support a central rather than a peripheral site of action.

Nocturnal magnetic field exposure: gender-specific effects on heart rate variability and sleep

OBJECTIVE

To determine if controlled exposure to power-frequency magnetic fields alters heart rate variability (HRV) and polysomnographic endpoints in healthy men (n=22) and women (n=24), 40-60 years of age.

METHODS

A randomized, double-blind, crossover design was used. Study endpoints collected during all-night exposure to 60 Hz magnetic fields at an occupational intensity (resultant flux density=28.3 microTesla, microT) were compared to similar endpoints obtained under equivalent, counterbalanced, no-exposure (< or =0.2 microT) control conditions.

RESULTS

Older men, but not women, exposed to the magnetic fields showed power reductions in the LF band of the HRV frequency spectrum, which is associated with sympathetically-mediated blood pressure and thermoregulatory control (P<0.04). Older women, but not men, exposed to the fields showed a pattern of disrupted sleep, with reductions in the duration of REM sleep (P=0.03), and strong trends for reductions in sleep efficiency (P=0.06) and total sleep time (P=0.06).

CONCLUSIONS

The gender-specific effects seen here with older volunteers replicate the results of previous exposure studies with younger men and women.

Exposure to strong ELF magnetic fields does not alter cardiac autonomic control mechanisms

Clinical and epidemiological studies attest that alterations in heart rate variability (HRV) are predictive of specific types of cardiovascular morbidity and mortality in otherwise healthy persons. Recent reports also suggest that changes in HRV may be associated with exposure to intermittent magnetic fields (60 Hz, 28.3 microT) in the laboratory and that mortality is increased in cardiac disease categories related to altered HRV for utility workers whose jobs involve longer exposure to elevated magnetic fields. This study combined three approaches to learn more about the specific exposure circumstances under which changes in HRV occur. First, cardiac autonomic control, as indexed by HRV spectral analysis measures, was measured in 24 men during exposure to a much higher intensity field than any previously examined (resultant flux density = 127.3 microT [1273 milliGauss, mG]). Second, HRV measures from the same individual were compared across three relevant test conditions: intermittent and continuous field exposure and during a no-exposure, control condition. Third, electrocardiographic data were analyzed to determine if the precise timing of when the magnetic field switched on or off in relation to the cardiac cycle results in phase-resetting of the human cardiac rhythm. HRV measures were not altered by either field exposure condition compared to the control condition, and no evidence for a phase-resetting mechanism was found. Further research is needed to resolve the differences between the present and the earlier laboratory-based studies of HRV and to determine if cardiac rhythm disturbances are associated with exposure to the more complex magnetic fields found in the man-made environment.

Staying on top of TB's rise

Delays in acid-fast bacillis (AFB) emergency department admissions prompted a revised multidisciplinary rounds process for weekends and holidays; AFB isolation cases dropped 10%.

Heart rate variability and physiological arousal in men exposed to 60 Hz magnetic fields

In previous research, intermittent exposure to sinusoidal 60 Hz magnetic fields at a resultant flux density of 28.3 microT was found to alter heart rate variability (HRV) in men during night sleep. When the 24 men in the present study were exposed under similar conditions, HRV was not altered. The previous studies included the hourly collection of blood samples via an indwelling venous catheter, while the present study did not. This may account for the observed differences in results. Further research is needed to determine if field exposure interacts with physiological arousal mechanisms to alter autonomic nervous system control over cardiac rhythms.

Hepatitis C

In the latter half of the 20th century, HCV emerged as the most common cause of chronic liver disease, and will likely remain so. Since its initial discovery in 1989, rapid progress has been made in our understanding of the virology, epidemiology, natural history, diagnosis, and treatment of HCV. Over the next few decades, as further advancements are made, superior treatment options will become available.

Cardiac autonomic control mechanisms in power-frequency magnetic fields: a multistudy analysis

Heart rate variability (HRV), a noninvasive indicator of autonomic control of cardiac activity, is predictive of long-term cardiac morbidity and mortality. Epidemiologic research suggests that occupational exposure to power-frequency magnetic fields may be associated with autonomically mediated cardiac mortality. Results from our laboratory studies of humans exposed to 60-Hz magnetic fields overnight, however, are inconsistent. HRV is altered in some studies but not others. To clarify this, the pooled data from seven studies involving 172 men were analyzed to test specific hypotheses concerning this inconsistency. After analysis, we excluded a) measurement drift or instability over time because HRV was stable under sham-exposed conditions across all studies; b) inadequate statistical power or failure to maintain double-blind controls; c) differences in field intensity (28.3 vs. 127.3 microT) or exposure pattern (intermittent versus continuous) as main effects; or d) the inclusion of individuals sensitive to magnetic field exposure in some studies but not others. Four separate analytic techniques failed to identify a valid subpopulation of sensitive individuals. In some studies, however, hourly blood samples were collected using an indwelling venous catheter. HRV alterations occurred during intermittent exposure in these studies (p < 0.05) but not in similar studies without blood sampling. This result suggests a field interaction with modest arousal or disturbance. Because HRV is tightly coupled to electroencephalographic activity during sleep, these results are physiologically plausible and suggest that HRV alterations during exposure to magnetic fields may occur when accompanied by increases in physiologic arousal, stress, or sleep disturbance.

Cardiac autonomic control mechanisms in power-frequency magnetic fields: a multistudy analysis

Heart rate variability (HRV), a noninvasive indicator of autonomic control of cardiac activity, is predictive of long-term cardiac morbidity and mortality. Epidemiologic research suggests that occupational exposure to power-frequency magnetic fields may be associated with autonomically mediated cardiac mortality. Results from our laboratory studies of humans exposed to 60-Hz magnetic fields overnight, however, are inconsistent. HRV is altered in some studies but not others. To clarify this, the pooled data from seven studies involving 172 men were analyzed to test specific hypotheses concerning this inconsistency. After analysis, we excluded a) measurement drift or instability over time because HRV was stable under sham-exposed conditions across all studies; b) inadequate statistical power or failure to maintain double-blind controls; c) differences in field intensity (28.3 vs. 127.3 microT) or exposure pattern (intermittent versus continuous) as main effects; or d) the inclusion of individuals sensitive to magnetic field exposure in some studies but not others. Four separate analytic techniques failed to identify a valid subpopulation of sensitive individuals. In some studies, however, hourly blood samples were collected using an indwelling venous catheter. HRV alterations occurred during intermittent exposure in these studies (p < 0.05) but not in similar studies without blood sampling. This result suggests a field interaction with modest arousal or disturbance. Because HRV is tightly coupled to electroencephalographic activity during sleep, these results are physiologically plausible and suggest that HRV alterations during exposure to magnetic fields may occur when accompanied by increases in physiologic arousal, stress, or sleep disturbance.

Human melatonin during continuous magnetic field exposure

This report describes the third in a series of double-blind, laboratory-based studies that were aimed at determining the effects of nocturnal exposure to power frequency magnetic fields on blood levels of melatonin in human volunteers. Our two earlier studies evaluated effects on melatonin of intermittent exposure to 60 Hz circularly polarized magnetic fields at 10 and 200 mG. No overall effects on melatonin levels were found. In the present study, men were exposed continuously rather than intermittently through the night to the same 200 mG magnetic field condition that was used previously; again, no overall effects on melatonin levels were found. We conclude that the intermittent and continuous exposure conditions used in our laboratory to date are not effective in altering nocturnal blood levels of melatonin in human volunteers.

Human sleep in 60 Hz magnetic fields

This report describes a double-blind, laboratory-based study of 24 healthy young men in which sufficient data were collected to examine the effects of intermittent versus continuous exposure to a 60 Hz, 28.3 microT magnetic field on multiple EEG measures of night sleep. Intermittent, but not continuous or sham exposure, was associated with less total sleep time, reduced sleep efficiency, increased time in Stage II sleep, and decreased REM sleep. Subjects exposed intermittently to the field also reported sleeping less well and feeling less rested in the morning than subjects in the other two groups. All observed effects were significant at P < or = .04 or less. The public health relevance of these results cannot be assessed as yet. Poor sleep quality, however, can have a detrimental influence on worker safety and performance, and has been associated with decrements in memory and learning processes. Additional research appears warranted.

Test facility for human exposure to AC and DC magnetic fields

For more than a decade, Midwest Research Institute (MRI) has investigated the effects of exposure to 60 Hz electric and magnetic fields (EMF) on human physiology, performance, and biochemistry. This accumulated experience, new research directions, and limited resources made it important to design more comprehensive and operationally cost-effective exposure facilities. Here we describe the new, integrated laboratory exposure test facilities recently constructed at MRI and present data on relevant characteristics of the exposure systems. Concentric coil systems were developed to generate uniform magnetic fields within the three new exposure rooms, with rapid cancellation of the field to ambient levels in the rest of the laboratory. Control systems are fully automated, computer-based, and independent. These provide the operational flexibility needed to present fields of different magnitudes, frequencies, and polarization. The local geomagnetic field can be modulated and/or canceled, and both AC and DC fields can be presented in various combinations. Capabilities for conducting double-blind experiments with true active-sham exposure conditions were implemented using bifilar windings and applying current flow in the opposite direction for each wire in a pair. The new facilities provide a comprehensive capability for laboratory-based human research on the potential effects of exposure to AC and DC magnetic fields.

Efficacy of laser-assisted uvulopalatoplasty

BACKGROUND AND OBJECTIVE

Laser-assisted uvulopalatoplasty (LAUP) is being used increasingly as a surgical treatment for snoring and obstructive sleep apnea (OSA). There is limited evidence for the success of LAUP in eliminating OSA. This study assesses the efficacy of LAUP in eliminating snoring and OSA and addresses which patients may be the best candidates for LAUP treatment.

STUDY DESIGN/MATERIALS AND METHODS

From January 1994 to January 1996, 297 patients were evaluated for snoring, with 190 (64%) exhibiting some degree of OSA documented by a PSG: 41/ 190 (22%) mild OSA; 33/190 (17%) moderate OSA; 85/190 (45%) severe OSA; 31/190 (16%) severity unknown. Ninety patients (90/ 297) have undergone LAUP treatment: 58/90 (64%) with OSA and 32/90 (36%) with snoring only.

RESULTS

Our results indicate a significant reduction of snoring in patients without OSA, but diminishing success in patients with increasing degrees of OSA. Additionally, LAUP was not efficacious in treating OSA: pre-op respiratory disturbance index (RDI) of 10.8 vs. post-op RDI of 19.5 for mild OSA (P = 0.14); pre-op RDI of 22.9 vs. post-op RDI of 25.4 for moderate OSA (P = 0.43); pre-op RDI of 56.8 vs. post-op RDI of 46.3 (P < 0.05), which is statistically but not clinically significant (i.e., RDI remained in the severe range).

CONCLUSION

We conclude that LAUP is an effective treatment for nonapneic snoring, but does not provide sufficient resolution of OSA, and based on our results, LAUP should be considered as an adjunctive therapy rather than a sole treatment for OSA in most cases.

Nocturnal exposure to intermittent 60 Hz magnetic fields alters human cardiac rhythm

Heart rate variability (HRV) results from the action of neuronal and cardiovascular reflexes, including those involved in the control of temperature, blood pressure and respiration. Quantitative spectral analyses of alterations in HRV using the digital Fourier transform technique provide useful in vivo indicators of beat-to-beat variations in sympathetic and parasympathetic nerve activity. Recently, decreases in HRV have been shown to have clinical value in the prediction of cardiovascular morbidity and mortality. While previous studies have shown that exposure to power-frequency electric and magnetic fields alters mean heart rate, the studies reported here are the first to examine effects of exposure on HRV. This report describes three double-blind studies involving a total of 77 human volunteers. In the first two studies, nocturnal exposure to an intermittent, circularly polarized magnetic field at 200 mG significantly reduced HRV in the spectral band associated with temperature and blood pressure control mechanisms (P = 0.035 and P = 0.02), and increased variability in the spectral band associated with respiration (P = 0.06 and P = 0.008). In the third study the field was presented continuously rather than intermittently, and no significant effects on HRV were found. The changes seen as a function of intermittent magnetic field exposure are similar, but not identical, to those reported as predictive of cardiovascular morbidity and mortality. Furthermore, the changes resemble those reported during stage II sleep. Further research will be required to determine whether exposure to magnetic fields alters stage II sleep and to define further the anatomical structures where field-related interactions between magnetic fields and human physiology should be sought.

A 6-Mb high-resolution physical and transcription map encompassing the hereditary prostate cancer 1 (HPC1) region

Several hereditary disease loci have been genetically mapped to the chromosome 1q24-q31 interval, including the hereditary prostate cancer 1 (HPC1) locus. Here, we report the construction of a 20-Mb yeast artificial chromosome contig and a high-resolution 6-Mb sequence-ready bacterial artificial chromosome (BAC)/P1-derived artificial chromosome (PAC) contig of 1q25 by sequence and computational analysis, STS content mapping, and chromosome walking. One hundred thirty-six new STSs, including 10 novel simple sequence repeat polymorphisms that are being used for genetic refinement of multiple disease loci, have been generated from this contig and are shown to map to the 1q25 interval. The integrity of the 6-Mb BAC/PAC contig has been confirmed by restriction fingerprinting, and this contig is being used as a template for human chromosome 1 genome sequencing. A transcription mapping effort has resulted in the precise localization of 18 known genes and 31 ESTs by database searching, exon trapping, direct cDNA hybridization, and sample sequencing of BACs from the 1q25 contig. An additional 11 known genes and ESTs have been placed within the larger 1q24-q31 interval. These transcription units represent candidate genes for multiple hereditary diseases, including HPC1.

Bacteraemia and antibiotic resistance of its pathogens reported in England and Wales between 1990 and 1998: trend analysis

OBJECTIVES

Determination of causes, trends, and antibiotic resistance in reports of bacterial pathogens isolated from blood in England and Wales from 1990 to 1998.

DESIGN

Description of bacterial isolates from blood, judged to be clinically significant by microbiology staff, reported to the Communicable Disease Surveillance Centre.

SETTING

Microbiology laboratories in England and Wales.

SUBJECTS

Patients yielding clinically significant isolates from blood.

MAIN OUTCOME MEASURES

Frequency and Poisson regression analyses for trend of reported causes of bacteraemia and proportions of antibiotic resistant isolates.

RESULTS

There was an upward trend in total numbers of reports of bacteraemia. The five most cited organisms accounted for over 60% of reports each year. There was a substantial increase in the proportion of reports of Staphylococcus aureus resistant to methicillin, Streptococcus pneumoniae resistance to penicillin and erythromycin, and Enterococcus faecalis and Enterococcus faecium resistance to vancomycin. No increase was seen in resistance of Escherichia coli to gentamicin.

CONCLUSIONS

Reports from laboratories provide valuable information on trends and antibiotic resistance in bacteraemia and show a worrying increase in resistance to important antibiotics.

Multi-night exposure to 60 Hz magnetic fields: effects on melatonin and its enzymatic metabolite

Magnetic field-induced suppression of nocturnal melatonin in humans has been reported in occupational and residential studies, but not in laboratory-based exposure studies. The present study examined whether this contrasting pattern of results might be related to associated differences in exposure duration or to field-induced measurement instability over time. Thirty healthy young men were evaluated using a randomized, double-blind test protocol. Statistical analysis indicated that 4 consecutive nights of exposure to power-frequency magnetic fields at occupational intensity (resultant flux density = 28.3 microtesla, muT, [283 milligauss, mG]) had no differential effect on concentrations of melatonin or its major enzymatic metabolite (6-hydroxymelatonin sulfate, 6-OHMS) in daily morning urine samples, compared to equivalent no-exposure sham control conditions. The consistency of intra-individual urinary measurements over the 4 test nights also was quite high (P < 0.01) in the sham control condition. In contrast, repeated nightly exposure to the magnetic field was associated with reduced consistency. Morning urinary measures obtained after exposure on night 4 differed (P < 0.01) from similar measures obtained after the second and third exposure night. Thus, while the overall results of this study do not support the melatonin hypothesis, there is some suggestion of a possible cumulative effect of magnetic field exposure on the stability of individual melatonin measurements over time. Additional research with longer periods of controlled exposure may be warranted.

Morning urinary assessment of nocturnal melatonin secretion in older women

We evaluated the feasibility of using morning urine samples in epidemiological studies aimed at clarifying the relationship between nocturnal melatonin levels and breast cancer risk. Initially, a laboratory-based study of 29 women (40- 70 yr old) was performed to examine the correlation between plasma melatonin levels in hourly nocturnal blood samples and both melatonin and its major enzymatic metabolite, 6-hydroxymelatonin-sulfate (6-OHMS) in morning urine samples. In a companion field study, morning urine samples were collected from 203 healthy women to assess similarities and differences in laboratory versus field measures. Taken together, our results indicate: 1) levels of melatonin and of creatinine-corrected 6-OHMS in the first morning void urine are strongly correlated with total nocturnal plasma melatonin output (P < 0.001) and also with peak nocturnal melatonin values (P < 0.001); 2) similar ranges for 6-OHMS were found in the laboratory and the field; and 3) neither menopausal status nor hormonal replacement therapy altered 6-OHMS values in morning void urine. The inclusion of morning urine samples in epidemiological studies of cancer could allow cost-effective, widespread testing of the role played by melatonin in human health and disease.

Measles inclusion-body encephalitis caused by the vaccine strain of measles virus

We report a case of measles inclusion-body encephalitis (MIBE) occurring in an apparently healthy 21-month-old boy 8.5 months after measles-mumps-rubella vaccination. He had no prior evidence of immune deficiency and no history of measles exposure or clinical disease. During hospitalization, a primary immunodeficiency characterized by a profoundly depressed CD8 cell count and dysgammaglobulinemia was demonstrated. A brain biopsy revealed histopathologic features consistent with MIBE, and measles antigens were detected by immunohistochemical staining. Electron microscopy revealed inclusions characteristic of paramyxovirus nucleocapsids within neurons, oligodendroglia, and astrocytes. The presence of measles virus in the brain tissue was confirmed by reverse transcription polymerase chain reaction. The nucleotide sequence in the nucleoprotein and fusion gene regions was identical to that of the Moraten and Schwarz vaccine strains; the fusion gene differed from known genotype A wild-type viruses.

Human exposure to 60-Hz magnetic fields: neurophysiological effects

The neurophysiological effects of exposure to power-frequency magnetic fields at two occupationally-relevant intensities were evaluated in a single-blind study with 18 male and 18 female volunteers. Auditory brainstem (BAEP) and somatosensory (SEP) evoked potentials were recorded before, during and after field exposure (duration = 45 min, frequency = 60 Hz, field intensities = 14.1 or 28.3 microtesla, microT), or an equivalent sham-exposure control period. Visual event-related potentials (VEP) to pattern reversal stimuli were also recorded before and after the exposure period. Field exposure had no differential effects on the BAEP, the VEP, or on SEP measures of central conduction time. Men and women showed a similar lack of sensitivity to exposure. The present results do not support the mechanistic hypothesis that the transmission of sensory information to appropriate cortical centers is delayed or distorted by exposure to power-frequency magnetic fields at occupational intensities.

Rapid identification of Mycobacterium bovis BCG by the detection of the RD1 deletion using a multiplex PCR technique

The BCG vaccine strain cannot, with confidence, be differentiated from other members of the Mycobacterium tuberculosis complex on phenotypic tests alone. Isolates from clinical sites not associated with vaccination may be confused with M. tuberculosis. A characteristic of BCG strains is the deletion of the genomic region RD1; detection of this forms the basis of a multiplex polymerase chain reaction (PCR) assay to distinguish BCG strains. In this study, 28 M. tuberculosis complex strains were analysed by the PCR assay. A DNA sequence displaying the characteristic deletion was detected in all eleven of the BCG strains tested and was not found in representatives of other members of the complex, including M. bovis. Thus, the assay affords a rapid, simple and effective method for the discrimination of the BCG vaccine strain from other members of the M. tuberculosis complex.

Using an annual over-75 health check to screen for depression: validation of the short Geriatric Depression Scale (GDS15) within general practice

OBJECTIVE

To validate the short Geriatric Depression Scale (GDS15) as a screening instrument and determine the optimal cutpoint for detecting depression among older people living in the community.

DESIGN

Two stage study with the first stage consisting of a health check of people aged 75 years and over by a practice nurse which included the GDS15. A second-stage diagnostic interview including the criterion standard was carried out blind to GDS15 score.

SETTING

A large general practice in Melton Mowbray, Leicestershire, UK.

PATIENTS

A random sample (stratified according to first-stage GDS15 score) of 257 older people living in the community, without significant cognitive impairment, were selected for the second-stage diagnostic interview.

MEASURES

The first-stage GDS15 score was compared with diagnostic status for depression and anxiety disorders (according to ICD-10 criteria) and presence of depressive symptoms at the second-stage clinical interview.

RESULTS

Ninety-three per cent of those eligible for the study were successfully screened with the GDS15. A cutpoint of <3/3+ had a sensitivity of 100% and specificity of 72% in detecting cases of depression but fewer than one in five of those testing positive reached a diagnostic threshold. Only 25% of those with a diagnosis of depression had any mention of mental health problems in their medical notes in the year prior to the clinical interview. For detecting depressive symptoms the same cutpoint was 79% sensitive and 78% specific with a positive predictive value of 46%.

CONCLUSIONS

Used as part of an annual over-75 health check in primary care, the GDS15 would detect a significant amount of hidden morbidity which would serve the original purpose of the annual elderly health checks in the UK.

Effective dose equivalent due to gamma-ray emissions from hot particles

The quantification of dose from hot particles in the nuclear power industry has received a good deal of attention in the past few years. Specifically, calculational models have been developed to determine shallow dose equivalent from both beta and gamma-rays (using VARSKIN) and to estimate deep dose equivalent based upon the gamma dose at a tissue depth of 1 cm. These two values are reported for regulatory purposes. The purpose of this study is to estimate another measure of dose from hot particles (or from skin contamination over a small area), specifically the effective dose equivalent which takes into account all organs of the body receiving appreciable dose from the gamma-ray emissions from the contamination. While it is generally recognized that this dose will be small, this study gives representative doses for a range of hot particle locations and gamma-ray energies. MCNP and the ADAM phantom have been used for the calculational model. The effective dose equivalent is found to range from 0.1 to 12 microSv h(-1) MBq(-1) (0.4 to 43 microrems h(-1) microCi(-1)) of gamma activity, depending upon the location of the hot particle on the body.