The effects of chronic industrial noise exposure on urinary cortisol, fatigue and irritability: a controlled field experiment

Effects of alpha-tocopherol on noise-induced hearing loss in guinea pigs

Preventing noise-induced hearing loss (NIHL) by antioxidants is based on the hypothesis that generation of reactive oxygen species is one of the causes of NIHL. alpha-Tocopherol is a naturally occurring antioxidant with no noticeable side effects. In this study, we attempted to protect guinea pigs from developing NIHL by administering alpha-tocopherol. Pigmented male guinea pigs were exposed to a noise (4 kHz octave band, 100 dB SPL), 8 h/day for 3 days consecutively. alpha-Tocopherol (10 mg/kg or 50 mg/kg daily) was given by intraperitoneal injection from 3 days before through 3 days after the noise exposure. Auditory evoked brainstem response (ABR) thresholds at 2, 4 and 8 kHz were recorded prior to the experiment, immediately post-noise, 2 and 8 days post-noise. On day 8 post-noise, after the ABR recording, guinea pigs were decapitated and the cochleae were removed for cochlear surface preparations and scanning electron microscope (SEM) study. ABR threshold shifts of groups receiving alpha-tocopherol were significantly smaller than those of groups not receiving alpha-tocopherol at all frequencies and all time points tested except that of group 3 at 8 kHz 8 days post-noise. No hair cell loss was seen on the surface preparations, but stereocilia loss was found by SEM study. The noise-induced stereocilia loss was significantly decreased by alpha-tocopherol. These results indicate that alpha-tocopherol can attenuate the noise-induced cochlear damage. Further investigations on the preventive effect of alpha-tocopherol on NIHL in noise-exposed workers are necessary.

Need for recovery in the working population: description and associations with fatigue and psychological distress

This study examined the concept of need for recovery, that is the need to recuperate from work-induced fatigue, experienced after a day of work. The study explored the relationship between need for recovery from work, prolonged fatigue, and psychological distress in the working population. A cross-sectional study was carried out. Data of the Maastricht Cohort Study on fatigue at work were used (n = 12,095). Some degree of need for recovery was found in nearly all employees. Need for recovery from work was associated with demographic, work-related, and health factors. Principal Components Analysis revealed obvious separation between need for recovery items and both fatigue items and psychological distress items, supporting the notion that need for recovery, fatigue, and psychological distress represent different underlying concepts. Although need for recovery, fatigue, and psychological distress were frequently comorbid, they also clearly occurred as separate entities.

Effects of nighttime low frequency noise on the cortisol response to awakening and subjective sleep quality

The effects of night-time exposure to traffic noise (TN) or low frequency noise (LFN) on the cortisol awakening response and subjective sleep quality were determined. Twelve male subjects slept for five consecutive nights in a noise-sleep laboratory. After one night of acclimatisation and one reference night, subjects were exposed to either TN (35dB L(Aeq), 50dB L(Amax)) or LFN (40dB L(Aeq)) on alternating nights (with an additional reference night in between). Salivary free cortisol concentration was determined in saliva samples taken immediately at awakening and at three 15-minute intervals after awakening. The subjects completed questionnaires on mood and sleep quality. The awakening cortisol response on the reference nights showed a normal cortisol pattern. A significant interaction between night time exposure and time was found for the cortisol response upon awakening. The awakening cortisol response following exposure to LFN was attenuated at 30 minutes after awakening. Subjects took longer to fall asleep during exposure to LFN. Exposure to TN induced greater irritation. Cortisol levels at 30 minutes after awakening were related to "activity" and "pleasantness" in the morning after exposure to LFN. Cortisol levels 30 minutes after awakening were related to sleep quality after exposure to TN. This study thus showed that night time exposure to LFN may affect the cortisol response upon wake up and that lower cortisol levels after awakening were associated with subjective reports of lower sleep quality and mood.

Chronic exposure of rats to cotton-mill-room noise changes the cell composition of the tracheal epithelium

The work environment of cotton mill rooms of modern textile plants is characterized by noise pollution. We have taped and reproduced this noisy environment to study its effects on experimentally exposed rats. Because we have previously documented that chronic noise causes alterations in the respiratory epithelium, we have focused our investigation on the morphology of the tracheal lining. Wistar rats were exposed to the textile-type noise from 1 up to 7 months, with an average 40 hours weekly exposure of the animals. The rats were sacrificed monthly and the tracheas were studied by scanning electron microscopy (SEM) to quantify the areas of the airway lining that were covered by ciliated, serous or other cells of the epithelium. We found that noise exposure of the rats caused a significant loss of tracheal ciliated cells; an increased density of serous cells on the epithelium balanced this change. This modification of the rat trachea was already established after 1 month of noise treatment of the animals; it did not change significantly throughout the 7-month course of the herein investigation. Loss of ciliated cells was more intense in areas of the tracheal epithelium located between the regions of cartilage rings. We conclude that the ciliated cell is an elective target for damage caused on the respiratory epithelium by the workplace noise occurring in cotton mill rooms. This modification of the respiratory epithelium is likely to impair clearance of the airways since this function depends on the activity of ciliated cells.

Psychoneuroendocrinological contributions to the etiology of depression, posttraumatic stress disorder, and stress-related bodily disorders: the role of the hypothalamus-pituitary-adrenal axis

Following the assumption that stressors play an important part in the etiology and maintenance of psychiatric disorders, it is necessary to evaluate parameters reflecting stress-related physiological reactions. Results from these examinations may help to deepen the insight into the etiology of psychiatric disorders and to elucidate diagnostic uncertainties. One of the best-known stress-related endocrine reactions is the hormonal release of the hypothalamic-pituitary-adrenal (HPA) axis. Dysregulations of this axis are associated with several psychiatric disorders. Profound hyperactivity of the HPA-axis has been found in melancholic depression, alcoholism, and eating disorders. In contrast, posttraumatic stress disorder, stress-related bodily disorders like idiopathic pain syndromes, and chronic fatigue syndrome seem to be associated with diminished HPA activity (lowered activity of the adrenal gland). Hypotheses referring to (a) the psychophysiological meaning and (b) the development of these alterations are discussed.

Combined effects of working environmental conditions in VDT work

The combined effects of city noise and luminance of the computer display were evaluated from the changes in lymphocytes and mental activities of participants. Healthy male students were tested under the following four experimental conditions: (1) a calculating task on a video display terminal (VDT) with luminance of 90 cd m(-2) without city noise; (2) a calculating task on a VDT with luminance of 20 cd m(-2) without city noise; (3) a calculating task on a VDT with luminance of 90 cd m(-2) with city noise of 70 dB(A); and (4) a calculating task on a VDT with luminance of 20 cd m(-2) with city noise of 70 dB(A). A visual reaction test (VRT) was performed, and critical flicker fusion frequency (CFF), heart rate (HR), numbers of circulating white blood cells (WBCs), lymphocyte subsets and subjective symptoms of fatigue were measured (1) before; (2) just after; and (3) 30 min after each 60 min test. Subjective symptoms of fatigue significantly increased just after experiments conducted under the two noisy conditions. VRT and CFF showed significant changes in the case of the high-luminance display with noise. WBCs and neutrophils showed significant increases in the two quiet conditions. These results suggested that high luminance with noise had the most effect on subjective fatigue and mental activities.

The influence of stressors on biochemical reactions--a review of present scientific findings with noise

For every faculty of perception there is, according to the degree of irritation, a biochemical or psychobiological activation. This is also true for the perception of sound or noise. Initially, these processes allow for the adjustment of the organism to a changed situation (eustress). Prolonged effects of stressors may ultimately lead to regulatory disturbances and induce pathological processes (distress). The pathogenetic concept that psychobiological stresses (e.g. noise) may be connected with the well-known risk factors of cardiovascular diseases, through excitation of the central nervous system, is based on the known stress models. The central connective factors are the activation hormones of the adrenal gland, also referred to as stress hormones. From blood and urine parameters recorded in epidemiological and experimental studies under the influence of acute or chronic noise, a simplified model of the pathogenetic mechanism has been developed. Fundamental conditions for future assessing the "stress hormones" have been derived, by means of which premorbid conditions can be determined on a population or group basis.

Chronic burnout, somatic arousal and elevated salivary cortisol levels

Burnout syndrome, comprised of the symptoms of emotional exhaustion, physical fatigue, and cognitive weariness, is believed to be a result of ineffective coping with enduring stress. This study of 111 nonshift blue-collar workers free of cardiovascular disease (CVD) examined whether chronic burnout is associated with a state of somatic and physiological hyperarousal. Results showed that 37 workers exhibited symptoms of chronic burnout, with symptoms lasting at least 6 months. These workers, compared to those with no burnout symptoms (n = 52) or nonchronic burnout symptoms (n = 22), had higher levels of tension at work, postwork irritability, more sleep disturbances and complaints of waking up exhausted, and higher cortisol levels during the work day. These results suggest that chronic burnout is associated with heightened somatic arousal and elevated salivary cortisol levels. This may be part of the mechanism underlying the emerging association between burnout and risk of CVD.

Physiological and emotional response to psychological stressors in psychiatric and psychosomatic disorders

Deviations from emotional and physiological homeostasis in humans occur under episodic, chronic, or traumatic stress experiences. These dysregulations can provoke emotional and physical disturbances that may result in stress-related psychiatric or psychosomatic disorders. This brief review discusses a variety of both naturally occurring and experimental stressors and the complexity of intervening variables on cardiovascular and hormonal dysregulations of the hypothalamic-pituitary-adrenal (HPA) axis. In addition to the type, intensity, and duration of the stressor, subject variables such as dispositional factors (e.g., age and sex), personality traits, and coping styles are considered. Finally, emotional and physiological stress responses to naturally occurring stressors and psychological challenge tests in depressed patients and anxiety disorder patients are presented and discussed. Stressors in humans induce emotional arousal, which leads to physiological activation of the central nervous system, an increase of hormones of the HPA axis, and coping reactions on the psychological and behavioral level. Depending on the type, intensity, and duration of the stressor, on personal and psychosocial resources of the individual, stressful situations may provoke emotional and physical disturbances. These dysfunctions may result in psychosomatic or psychiatric disorders. The following brief review intends to discuss a variety of stressors that have been examined in humans in order to gain insight into the complex relationship between physiological and behavioral stress reactions and the occurrence or maintenance of stress related psychosomatic and psychiatric disorders.