Charles Graham

Use of the McGill Pain Questionaire in the assessment of cancer pain: Replicability and consistency

&NA; The McGill Pain Questionnaire (MPQ) is a recent empirically derived instrument designed to provide quantitative information on major dimensions of pain. Although widely used as an outcome measure in clinical research, little attention has been directed specifically at the instrument itself. The present study addressed this need. Detailed findings were obtained for both single and multiple administrations of the MPQ in two subject samples, each composed of 18 cancer outpatients in pain. These data were compared to similar, but less extensive, data reported by Melzack [6]. MPQ indices proved highly replicable over the two subject samples tested and were remarkably similar to the findings reported by Melzack for a different cancer pain patient sample. No differences were found between the written form of MPQ administration used in the present study and the oral procedure followed by Melzack. The consistency of pain descriptor subclass choice in the present samples was high, ranging from 66% to 80.4% over 4 administrations, and these values compare well with the value of 70.3% reported earlier by Melzack. However, the present subjects selected a larger set of pain descriptor words compared to the word set reported to be characteristic of cancer pain by Dubuisson and Melzack [2]. Both individual and group analyses indicated the MPQ is best used as a measure of immediate pain, and not as a summary measure of past pain over a defined period of time. These findings support the use of the MPQ as a reliable, multi‐dimensional measure of immediate pain, and suggest the potential value of future research aimed at refining the psychometric properties of the instrument.

Prediction of nocturnal plasma melatonin from morning urinary measures

Abstract: A growing literature indicates that blood levels of the hormone melatonin may have important implications for human health and wellbeing. Melatonin is synthesized and released into the general circulation at night, however, and it is seldom feasible to draw blood samples at night in epidemiological studies. There is some evidence that levels of urinary melatonin and of 6‐sulfatoxymelatonin (aMT6s), the major metabolite of melatonin, accurately reflect nocturnal plasma melatonin. If this is the case, urinary assays could be powerful tools for epidemiological studies. A laboratory‐based study was performed to examine the relationships between nocturnal plasma melatonin, morning urinary melatonin, and morning urinary aMT6s levels in 78 men. The relationship between total nocturnal plasma melatonin and both urinary aMT6s corrected for creatinine and urinary melatonin is significant. Combining the two urinary measures accounts for 72% of the variance in total plasma melatonin. Peak nocturnal plasma melatonin also was significantly related to urinary melatonin and to aMT6s. The urinary measures show good sensitivity and specificity in identifying individual differences in nocturnal plasma melatonin levels. These results support the inclusion of morning urine samples to assess the contribution of the hormone melatonin in occupational or residential studies involving healthy, young men.

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.

NOCTURNAL MELATONIN LEVELS IN HUMAN VOLUNTEERS EXPOSED TO INTERMITTENT 60 HZ MAGNETIC FIELDS

Two double-blind laboratory-based studies were performed to determine whether a suppression of nocturnal melatonin similar to that observed in rodents occurs when humans are exposed to magnetic fields at night. In study 1, 33 men were exposed to sham, 10 mG, or 200 mG intermittent, circularly polarized magnetic fields from 2300 to 0700 h under controlled environmental and exposure test conditions. Overall, exposure had no effect on melatonin levels. Men with preexisting low levels of melatonin, however, showed significantly greater suppression of melatonin when they were exposed to light and also when they were exposed to the 200 mG magnetic-field condition. Study 2 directly tested the hypothesis that low-melatonin subjects show enhanced sensitivity when exposed to light and to 200 mG magnetic fields. After preexposure screening, each of 40 men slept in the exposure facility on two nights. On one night, the men were sham exposed. On the other night, they were exposed to the 200 mG field condition used previously. Again, exposure had no overall effect on melatonin levels. The original finding of enhanced sensitivity in low-melatonin subjects was not replicated in this study. We conclude that the intermittent exposure conditions used in these two studies were not effective in altering nocturnal melatonin release patterns in human volunteers. Further research is underway with regard to exposure parameters, hormonal and immune system measures, and individual differences.

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.

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.

Self-report of circadian type reflects the phase of the melatonin rhythm.

This study examined the relationship between circadian rhythm characteristics of the pineal hormone melatonin and individual differences in circadian type and mood. 95 healthy young men and 22 women were assessed each hour (00:00-07:00 h) for blood levels of melatonin throughout one night in the laboratory. Each subject was assessed for circadian type (morning, afternoon, or evening type) and morning mood (PANAS). Circadian type was strongly related to the melatonin acrophase but not to amplitude or time of year of assessment. Also, morning types evidenced a more rapid decline in melatonin levels after the peak than did evening types. Evening types were younger than were morning types. Female morning types reported more positive affect upon waking than did female afternoon or evening types. Males showed no such discrimination. Age was related to both melatonin acrophase and circadian type but did not explain the relationship between them. The results replicate and extend findings on circadian type and psychological and physiological variables.

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, μT, [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.

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.

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.