Stress reduction and preventing hypertension: preliminary support for a psychoneuroendocrine mechanism

Our objective was to identify endocrine-related mechanisms capable of mediating preventive effects of stress reduction in hypertensive heart disease. Since beneficial effects of stress reduction accrue over time, this cross-sectional, descriptive study sought differences between healthy students not practicing a systematic technique for reducing stress (the average stress, or AS, group, n = 33) and a similar group who for 8.5 years had practiced the Transcendental Meditation (TM) technique, used widely to reduce stress (the low stress, or LS, group, n = 22). The two groups of students, matched for age and area of study, performed timed collections of urine that included (separately) the entire waking and sleeping portions of 1 day. They also completed the Profile of Mood States and the State-Trait Anxiety Inventory, self-report instruments sensitive to subjective level of stress. Urine samples were analyzed for adrenocortical steroids by radioimmunoassay, for Na+, K+, Mg2+, Ca2+, and Zn2+ by atomic absorption spectrometry, and for neurotransmitter metabolites by reverse-phase, high-performance, liquid chromatography, and spectrophotometry. The two groups differed significantly on most measures. Specifically, the LS group was lower in cortisol and aldosterone and higher in dehydroepiandrosterone sulfate (DS) and the serotonin metabolite, 5-hydroxyindoleacetic acid (5-HIAA). Excretion of sodium, calcium, zinc, and the norepinephrine metabolite, vanillylmandelic acid (VMA), was also lower in this group, as were Na+/K+ ratio, mood disturbance, and anxiety. In women practicing TM, cortisol correlated inversely and DS directly with number of months of TM practice. The results identify improvements in mood state, adrenocortical activity, and kidney function as probable factors in the preventive and treatment effects of stress reduction. Because suboptimal levels of these parameters result from chronic, subjective stress, the findings add mechanistic support to the contention that hypertensive heart disease is avoidable, even in modern industrialized societies.

Chronic immobilization stress reduces sodium intake and renal excretion in rats

The influence of chronic exposure to immobilization (IMO) on sodium appetite as well as sodium and potassium renal excretion in adult male Wistar rats was studied. The animals were individually housed and all variables under observation were measured in metabolic cages the first, seventh, and thirteenth days once the experiment had started. Half of the rats had access to water, and the remainder of the rats had access to both water and saline solution (1.5% NaCl). IMO reduced the intake of saline solution. Renal water, sodium, and potassium excretion in those IMO rats having access to saline were lower than in control rats. The effects of IMO were very similar during all observation days; therefore no evidence of adaptation to repeated stress was found. The present data indicate the following: (i) IMO stress reduced sodium appetite, probably as a secondary effect to the deficit in sodium renal excretion; (ii) IMO caused antidiuresis and antikaliuresis, only in those rats taking saline solution; (iii) no adaptation to repeated IMO stress was found in any of the tested variables. The reduction of sodium appetite observed in stressed rats might be a homeostatic mechanism to maintain sodium balance after impairment of renal sodium excretion caused by stress.

Urinary catecholamine levels and dentofacial injuries in children

This study investigated the relationship between urinary catecholamine levels and dentofacial injuries in 221 children, boys and girls, aged 8 to 10 years. Dentofacial injuries were recorded by a questionnaire and a clinical examination. Three 24-h urine samples, taken with an interval of 1 year between each, were available for each subject. A representative urine sample from each examination was analyzed by the high-performance liquid chromatography technique to assay the catecholamine content. Socioeconomic factors were recorded by a questionnaire. Of the examined children 58 (24 boys and 34 girls) with complete 24-h urine samples showed neither historical nor clinical evidence of dentofacial injuries and constituted the control group. Two case groups, A and B, with historical and/or clinical evidence of dentofacial injuries were matched by age and gender. Differences in the quantitative and qualitative data were tested by the paired t-test and the chi 2 test, respectively, while a regression analysis was applied to measure the effects of norepinephrine on epinephrine and dopamine. The 95% probability level was used. The results showed significant differences between control and case group A in the epinephrine and norepinephrine levels of the second urine sample. Significant differences were also found between control and case group B at the first urine sample in epinephrine and dopamine and at the second in epinephrine. Injured boys had significantly higher values of all catecholamines except for epinephrine in the second urine sample than injured girls. The only significant difference found between boys and girls without dentofacial injuries was in norepinephrine in the second urine sample. The data suggested that children with dentofacial injuries are more frequently under emotional stress and consequently emotionally stressful children run a greater risk of sustaining such injuries.

Chronic psychosocial stress does not affect the number of pyramidal neurons in tree shrew hippocampus

Exposure of the hippocampus for prolonged periods to an excess of glucocorticoids is thought to result in damage and finally loss of pyramidal neurons. By applying improved methods for quantifying cell numbers we investigated whether chronic psychosocial stress in tree shrews reduces the total number of hippocampal pyramidal neurons. For 28 days male tree shrews were exposed to subordination stress resulting in constantly elevated cortisol levels. The number of pyramidal neurons in the hippocampal fields CA1 and CA3 was estimated with the optical fractionator technique. In both hippocampal fields, neuron number in the stressed subjects was not significantly altered in comparison to unstressed controls. This constancy of neuron number represents an essential finding for identifying the effects of chronic stressful conditions on hippocampal structure.

[The effect of loading tests on the activity and reactivity of the sympathetic-adrenal system in subjects with arterial hypertension and overweight]

Regulatory potentialities were studied of the sympathetic-adrenal system that reveal themselves in response to psychoemotional testing and acute peroral salt loading. In the group of over-weight (OW) patients presenting with hypertensive disease (HD), 1-h excretion of catecholamines following the psychoemotional testing was not different from that during the testing itself, which fact suggests more prolonged reaction of the sympathetic-adrenal system to stress in these examinees. An acute peroral salt loading causes increase in activity of the hormonal and mediator links of the sympathetic-adrenal system in HD patients both overweight and in the normal range body weight (BW). It was only those persons presenting with normal BW that were retaining sodium after the test.

Psychosocial stress and urinary cortisol excretion in marmoset monkeys (Callithrix kuhli)

Activation of the hypothalamic-pituitary-adrenal (HPA) axis is one of the hallmarks of the physiological responses to psychosocial stressors. The most common method of assessing HPA function is via the measurement of plasma cortisol levels. However, venipuncture involves capture and restraint, which can modify HPA function. We validated a noninvasive procedure for monitoring HPA responses to stressors by measuring excretion of free urinary cortisol. Samples collected throughout the day displayed marked circadian variation, with low cortisol values in first-void samples, followed by a mid-morning peak in cortisol excretion. Concentrations of excreted cortisol declined throughout the day. Exposing marmosets to mild and moderate stressors (11 h isolation in a small cage and manual restraint) increased excreted cortisol concentrations in a dose-dependent fashion: isolation in a small cage led to elevated cortisol in afternoon samples, while manual restraint and isolation produced elevated cortisol in both morning and afternoon samples. The marmoset HPA is differentially sensitive to rather subtle variations in stressors, and these results show that urinary cortisol excretion is a valid and sensitive index of the HPA response to these stressors.

[Hormonal response to stress after cerebrovascular accident: relation to type, size and site of the lesion]

OBJECTIVE

To study the relationship between the hormone response to stress seen after ACV (CVA) and the type, size and site of the lesion.

MATERIAL AND METHODS

We made a prospective study of the relationship between stress hormones and the radiological characteristics of the lesion in 82 patients admitted to hospital for non AIT ACV (CVA). We assessed the 24 hour urine catecholamines (total catecholamines, adrenaline, noradrenaline, vanillylmandelic acid, metanephrines and dopamine) and the 24 hour urine cortisol, collected on the second and third day after admission respectively. The type, size and site of the lesions were studies on CT scans done between 3 and 7 days after admission.

RESULTS

We studied 82 patients, 43 men and 39 women with an average age of 71.7. In 7 patients the lesion was parenchymatous haemorrhage; in 75 it was an infarct, which was small (< 6 cm3) in 30.5%, moderate sized (6-60 cm3) in 38.6% and large in 30.6%. In the cases of infarct, only the cortisol was significantly different in the three groups (average (DE) standard deviation, respectively: 80.6 (50), 114 (124) and 246 (207); p = 0.0014). This relationship persisted when the cortisol level was compared with the volume in cm3 (p = 0.0028). The cortical infarcts had significantly higher levels of cortisol than the more deeply situated infarcts (83.2 (55) as compared to 174 (184); p = 0.0321), but the latter were smaller and no difference was seen when size was taken into account. All findings were similar in haemorrhages and infarcts of equal size.

CONCLUSIONS

There was no relationship between the catecholamines and the type or size of the lesion. In our series, the site of the lesion did not appear to have any effect on the characteristics or intensity of the hormone response.

Psychological stress induced by 20 days bed rest

We investigated the changes of the psychological state during 20 days bed rest (BR) in 10 young participants,(5 males and 5 females, age; 19-24 yrs). Psychological assessment was accomplished by the following authorized 3 indices: 1) Zung's Self-rating Depression Scale, 2) Cornell Medical Index, and 3) Goldberg's General Health Questionnaire. Zung's Self-rating Depression Scale is a indicator for depression, and the other two indices were used for detecting signs of neurosis. The results from Zung's Self-rating Depression Scale and the General Health Questionnaire in this study indicated a tendency toward depression and neurosis developing during BR, respectively. The scores in the Cornell Medical Index did not change. Urinary excretion of 17-hydroxycorticosteroid increased significantly, indicating that BR immobilization induced an important psychological stress. We were unable to determine which factors caused the changes in psychological state during BR, immobilization insert or personal problems.

Acute withdrawal of nasal CPAP in obstructive sleep apnea does not cause a rise in stress hormones

We hypothesized that withdrawal of nasal continuous positive airway pressure (CPAP) in patients with sleep apnea would produce a measurable stress response. To test this hypothesis, we ceased CPAP in eight patients regularly using nasal CPAP long term and measured the effect on sleep apnea as well as plasma and urinary levels of the stress hormones, noradrenaline, cortisol and adrenocorticotropic hormone (ACTH). CPAP withdrawal led to an immediate recurrence of sleep apnea with increases in apnea index, arousal index and oxygen desaturation (all p < .0001) but no change in levels of noradrenaline, cortisol or ACTH. We conclude that acute withdrawal of CPAP in patients with sleep apnea does not lead to a classic stress response.

Lower sex hormones in men during anticipatory stress

Free cortisol, luteinizing hormone (LH), total testosterone and monoamines were measured in two successive nocturnal urine collections in 50 healthy men to assess the influence of anticipatory stress. The first collection (N-2) was two nights before and the second (N-1) was just on the night before a one-day experimental stressor consisting of participation in a one-day clinical research protocol. The mean cortisol level increased from 23.4 (N-2) to 66.6 micrograms (N-1), while mean LH level decreased from 2.68 (N-2) to 1.71 IU (N-1) and the mean testosterone level fell from 1.31 (N-2) to 0.70 microgram (N-1). There were no changes in monoamines. Inhibition of sex hormones is a relatively neglected area of stress research.

Altered cortisol response in sober alcoholics: an examination of contributing factors

We have previously reported an attenuated plasma cortisol stress response in alcoholics abstinent from alcohol up to 4 weeks. The present study replicates and extends these findings by examining urinary cortisol levels in detoxified alcoholics (n = 40) and controls (n = 14) at rest and following mental arithmetic and isometric handgrip stress. Although the groups had similar baseline cortisol levels, the alcoholics showed an attenuated cortisol response to the combined stressors. This cortisol response reduction was unrelated to potential confounds such as smoking, liver function, age, depression, or anxiety. A multivariate model showed a trend for an association between severity of withdrawal and alcoholics' poststress cortisol levels. Although these results indicate decreased adrenocortical response to biobehavioral stress in alcoholics abstinent up to four weeks, higher stress cortisol values were seen in the patients with the most severe withdrawal symptoms.

Urinary output of endogenous monoamine oxidase inhibitory activity is related to everyday stress

The MAO A and B inhibitory components of urinary tribulin were investigated in normal individuals (11 males and 24 females, mean age +/- SD; 27.1 +/- 4.5 years) in relation to everyday stress. Volunteers collected a urine sample at the same time (late evening) on five days over a single week. On each occasion subjects also completed a mood adjective checklist which measured perceived stress levels over the day in question. For each subject all daily measures were aggregated. Mean individual urinary MAO A and B inhibitory activity was found to be positively correlated with stress scores both before (r = 0.38, p < 0.05 and r = 0.37, p < 0.05 respectively, n = 35) and after (r = 0.35, p < 0.05 and r = 0.33, p < 0.05 respectively, n = 35) correction for the effects of urinary volume. These results suggest that in normal healthy individuals high endogenous MAO inhibitory activity in the urine is indicative of a relatively enduring state of everyday stress.

Changes in urinary excretion of catecholamines and their metabolites in pediatric dental patients

To explain the changes in urinary excretion of catecholamines and their metabolites in pediatric dental patients, comparative measurements of three catecholamines (dopamine, noradrenaline and adrenaline), and five metabolites (3, 4-dihydroxyphenylacetic acid, normetanephrine, metanephrine, homovanillic acid, and vanillylmandelic acid) were made before and after dental treatment. The investigations were carried out in seven healthy young children between three and five years of age. All these children had previously displayed negative behavior in dental treatment. There were statistically significant increases (P < 0.05) in urinary noradrenaline, adrenaline, and normetanephrine levels during dental treatment. These results suggest that these three substances could be a useful tool for determining the occurrence of dental stress in children.

Neuroendocrine and immunological responses of women to stress

Natural killer (NK) cell activity, cortisol and catecholamine levels, and physiological reactivity were examined in 15 healthy women who volunteered to take a cognitive stress test (the Stroop test). Relationships were explored among the physiological and selected psychosocial variables. Urine and blood samples were taken to examine catecholamine and cortisol concentrations and NK cell activity immediately before, immediately after, and hourly for 6 hours after the Stroop test. During the Stroop test, heart rate, skin conductance, peripheral skin temperature, and blood pressure were measured. Although skin conductance, heart rate, and blood pressure increased in response to the Stroop test, neuroendocrine values did not. Cortisol secretion decreased after the Stroop test and appeared to follow the normal circadian rhythm. NK cell activity was variable among individual participants but tended to increase over time.

Urinary catecholamine levels in children with and without a history of dentofacial injuries

This study was conducted to investigate the existence of any differences in the urinary catecholamine levels in children with and without a history of dentofacial injuries. Three hundred fourteen children, boys and girls, aged 6 to 8 years were included in this study. A questionnaire was distributed to the parents to collect information about the child's history of dentofacial injuries. A 24-h urine sample was collected for each subject and a representative sample (25 ml) was analyzed by the HPLC technique to assay the catecholamine content. Of the examined children 68 (43 boys and 25 girls) had a history of dentofacial injury and constituted the experimental group. A control group of 68 children (43 boys and 25 girls) without a history of dentofacial injury was matched by age and sex. The Student t-test was used to identify any differences in urinary catecholamine levels between the two groups. The 95% probability was used. The results showed statistically significant differences in the mean values of epinephrine, while the differences in norepinephrine and dopamine were not significant. This study suggested that children with emotionally stressful states run a greater risk of having dentofacial injuries.

Low urinary cortisol excretion in Holocaust survivors with posttraumatic stress disorder

OBJECTIVE

The authors' objective was to compare the urinary cortisol excretion of Holocaust survivors with posttraumatic stress disorder (PTSD) (N = 22) to that of Holocaust survivors without PTSD (N = 25) and comparison subjects not exposed to the Holocaust (N = 15).

METHOD

Twenty-four-hour urine samples were collected, and the following day, subjects were evaluated for the presence and severity of past and current PTSD and other psychiatric conditions.

RESULTS

Holocaust survivors with PTSD showed significantly lower mean 24-hour urinary cortisol excretion than the two groups of subjects without PTSD. Multiple correlation analysis revealed a significant relationship between cortisol levels and severity of PTSD that was due to a substantial association with scores on the avoidance subscale.

CONCLUSIONS

The present findings replicate the authors' previous observation of low urinary cortisol excretion in combat veterans with PTSD and extend these findings to a non-treatment-seeking civilian group. The results also demonstrate that low cortisol levels are associated with PTSD symptoms of a clinically significant nature, rather than occurring as a result of exposure to trauma per se, and that low cortisol levels may persist for decades following exposure to trauma among individuals with chronic PTSD.

Lorry drivers' work stress evaluated by catecholamines excreted in urine

OBJECTIVES

To evaluate lorry drivers' work stress by measurement of adrenaline and noradrenaline excreted in the urine, and to find out which factors in their working situation are related to the excretion rates of these catecholamines.

METHODS

The urinary excretion of adrenaline and noradrenaline of 32 lorry drivers, who also had loading and unloading activities to perform, was studied for one working day and one rest day. Each driver was asked to provide six urine samples on both days.

RESULTS

For all samples, except the first (overnight) sample, the excretion rates of both catecholamines on the working day were higher than those on the rest day. Hierarchical multiple regression analyses were carried out to find out which factors in the drivers' working situation were related to the excretion rate of the working day. The excretion rate of adrenaline on the rest day, age, and psychosomatic complaints were positively related to the excretion rate on the working day (all P < 0.05). Body mass index and physical workload during loading and unloading were positively related to noradrenaline excretion rate (both P < 0.01). Psychosocial job strain did not significantly contribute to the proportion of variance explained in the excretion rates of both catecholamines.

CONCLUSIONS

The excretion rates of adrenaline and, especially, noradrenaline on the working day were higher than those found in earlier studies among professional drivers and insufficient recovery took place after the work was ended. The only association between excretion rate on the working day and work stressors was found for noradrenaline and physical workload. The drivers' sympathoadrenal medullary reactivity to everyday work demands shows the characteristics of sustained activation.

Response to psychological stressors in hand-arm vibration syndrome patients

We investigated urinary catecholamines' response to acute psychological stress test in hand-arm vibration syndrome patients. Thirteen patients with vibration-induced white finger (VWF) in higher frequency of attack, 7 patients with VWF in lower frequency, 6 patients without VWF and 17 healthy subjects were examined. All subjects were male and their average age (SD) was 59.2 (6.4), 56.3 (2.9), 58.2 (4.7) and 56.8 (4.9), respectively. After an initial rest for 1 hour, acute psychological stress test with stressors--mirror drawing, watching horror video and arithmetic under intermittent noise was performed for 1 hour. Subjective complaints to the stress test were greater in patients with hand-arm vibration syndrome than in the healthy controls. The patient group with VWF in higher frequency indicated significant increases of urinary catecholamines (p < 0.05); average values (SD) at rest period and at stress test were 2.42 (1.17) and 3.71 (1.82) micrograms/h for norepinephrine, and 1.47 (0.73) and 2.66 (1.79) micrograms/h for epinephrine, respectively. Increasing tendency of urinary catecholamines was observed in other three groups, however, they were not statistically significant. The sympathoadrenal medullary response to psychological stressors increased especially in hand-arm vibration syndrome patients with VWF in higher frequency.

The Quieting Response (QR): A Modality for Reduction of Psychophysiologic Stress in Nursing Students

The purpose of this study was to investigate the effects of a 5-week stress management program for 40 junior baccalaureate nursing students. A quasi-experimental pretest-posttest control group design was used. The stress management group included training sessions using cognitive modification techniques and Stroebel's Quieting Response (QR) augmented with biofeedback techniques for self-relaxation. A significant reduction of state anxiety (P < .001) was reported on the State-Trait Anxiety Inventory (STAI) by the experimental groups, while the state anxiety of the control groups remained relatively unchanged. There were no significant changes in trait anxiety scores. Urinary potassium excretion was measured as an index of the adrenal stress response. Findings revealed no statistically significant correlation between potassium excretion and scores on the STAI. These results support the benefits of integrating a stress management program into curricula for nursing students.

Meditation, melatonin and breast/prostate cancer: hypothesis and preliminary data

The objective of this study was to test the hypothesis that the regular practice of mindfulness meditation is associated with increased physiological levels of melatonin. Melatonin may be related to a variety of biologic functions important in maintaining health and preventing disease, including breast and prostate cancer. Previous studies have shown melatonin production is photosensitive and we suggest here that it also may be psychosensitive. A cross-sectional study of 12-hour (20:00-08:00) urinary 6-sulphatoxymelatonin was conducted from which we analyzed data from 8 women who regularly meditate (RM) and 8 women who do not meditate (NM). All samples were collected in the homes of study participants. Volunteers were recruited to provide 12-hour overnight samples of urine. All subjects collected the samples on one night during the same 1-week period. There was no explicit intervention. However, all RM were either graduates of, or teachers in, the University of Massachusetts Stress Reduction and Relaxation Program. The main outcome measure was the total excretion of urinary 6-sulphatoxymelatonin. Multiple linear regression (Proc GLM in SAS) was performed to test the effect of meditation (RM vs NM) on 6-sulphatoxymelatonin. The results of the study were that after controlling for the non-significant effect of menstrual period interval, we found an effect of meditation group (RM vs NM: b = 1.983; F = 6.78; p = 0.02) and age (for each integer year: b = 0.169; F = 8.41; p = 0.01). The conclusion is that study results are consistent with our hypothesis and indicate that melatonin might be a useful parameter in testing similar psycho-social interventions.(ABSTRACT TRUNCATED AT 250 WORDS)

Urinary free cortisol values in children under stress

Children with adrenocortical insufficiency are commonly instructed to increase their baseline glucocorticoid replacement doses by three to five times during periods of stress such as surgery or febrille illness. We conducted this to determine whether these recommendations reflect the actual change in urinary free cortisol (UFC) output during stress. The 24-hour UFC excretion was determined in 78 children who were admitted to a general pediatric department or intensive care unit with temperature > 38.7 degrees C, after major surgery, or during status epilepticus; we reevaluated 43 of the patients 2 weeks after recovery. In addition, the 24-hour UFC levels were determined in 127 healthy children aged 1.8 to 17 years. The UFC level positively correlated with age (r = 0.254; p < 0.001). The amount of UFC per gram of creatinine was inversely correlated with age (r = 0.255; p < 0.001). The amount of UFC per surface area was independent of age. The mean change in the level of UFC per square meter surface area was highest among children who had cardiothoracic surgery and those with multiple trauma. The increase in UFC level during bacterial infection was significantly greater than that during viral infection. The current recommendation to increase the dose to three to five times the baseline glucocorticoid dose during times of stress may underestimate the changes in UFC found in some patients with major surgery, trauma, or certain serious bacterial infections. Production rate studies are needed to prove this point.

Cancer stressors and protective factors: predictors of stress experienced during treatment for childhood cancer

Perceptions of cancer stressors and protective factors are predictors of stress experienced during treatment for childhood cancer were assessed in this study. Cancer stressors were the type of treatment received during two clinic visits and the child's perception of the cancer experience. Protective factors were self-perception, coping strategies, perceived social support, and family environment. The child's responses to stressors were assessed by epinephrine, norepinephrine, and cortisol levels of urine, and measures of state anxiety. Forty-four children between 6 1/2 and 13 1/2 years of age receiving treatment for cancer were evaluated during two clinic visits. Epinephrine was elevated for children during both clinic visits, while norepinephrine and cortisol remained normal. Stepwise multiple regression analyses revealed that the family environment and global self-worth were the best predictors of epinephrine levels, while social support from friends predicted norepinephrine levels. The family environment and social support from teachers predicted state anxiety.

Psychophysiological responses of parents to pediatric critical care stress

Psychological factors are associated with how parents cope during a child's intensive care hospitalization. However, little is known about the role of physiological-stress responses in parents' coping and adaptation to such situations. This study investigates the relationship between parents' psychophysiological-stress responses, as measured by urine catecholamine excretion, and their coping and activities during a child's intensive care experience. Parents who appraised the situation as one that is amenable to change and who used more problem-focused strategies, such as seeking social support, had lower anxiety and lower catecholamine levels. Further, parents who were more problem focused performed more child care activities during the experience. The results of this study provide information for planning interventions to promote parental coping and adjustment to the child's critical care situation.

Neuroendocrine responses of flight cadets during midterm tests and of fighter pilots during tail chase sorties

Urinary excretion of catecholamines (CA), epinephrine (E), and norepinerphrine (NE) was determined in flight cadets (n = 46) during mid-term test sorties and was compared with the measures of these variables in fighter pilots (n = 65) during tail chase sorties. Flight cadets were divided into passed and failed cadets. Fighter pilots were divided into superior, above average, and average with flying ratings of > 7, 6-7, and <6, respectively, and with flying experience of 2050 +/- 1081 h, 884 +/- 575 h, and 616 +/- 756 h, respectively. CA excretion data showed significant intra- and intergroup differences. Excretion rates for CA and NE before and after flight were significantly higher in flight cadets than in fighter pilots. After flight, all the preflight urinary variables increased significantly in passed flight cadets, while changes in failed flight cadets were not significant. In all groups of fighter pilots, preflight excretion rates for CA, E, and NE rose postflight, but the differences within the groups were not significant. The NE/E ratio decreased significantly as a function of flight adaptation. The pre- and postflight NE/E ratios were lower in fighter pilots than in flight cadets. The delta NE/E ratio decreased in fighter pilots, but increased in flight cadets. The preflight NE/E ratio was smaller for superior than for above average and average fighter pilots, and for passed than for failed flight cadets. The postflight NE/E ratio did not show any significant differences within the groups. In superior fighter pilots, the delta NE/E ratio remained relatively stable, while it was reduced in above average and average fighter pilots.(ABSTRACT TRUNCATED AT 250 WORDS)