Sound conditioning has reduced noise-induced hearing loss in experimental mammalian animals and in clinical observation. Forty guinea pigs were grouped as: A, control; B, conditioning noise exposure group; C, high level noise exposure group; and D, conditioning noise exposure followed by a high level noise exposure group. Auditory brainstem response thresholds were measured. The cochlear sensory epithelia surface was observed microscopically. Calmodulin, F-actin and heat shock protein 70 (HSP70) in hair cells were immunohistochemistrically stained. The intracellular free calcium was stained for confocal microscopy. The ABR threshold shift after noise exposure was higher in group C than D, and showed a quicker and better recovery in group D than C. Stereocilia loss and the disarrangement of outer hair cells were observed, with the greatest changes seen in group C, followed by groups D and B. The most intensive immunohistochemical intracellular expressions of calmodulin, F-actin, and HSP70 were found in group D, followed by groups C, B and A. The highest intensity of the fluorescent intracellular free Ca2+ staining in the isolated outer hair cells was observed in group C. The ABR and morphological studies confirmed the protective effect from noise trauma of sound conditioning. The protective mechanism of hair cells during sound conditioning was enforced through the increase of cellular cytoskeleton proteins and through the relieving of intracellular calcium overloading caused by the traumatic noise.
Shift work has been associated with increased risk of cardiovascular disease. This study was designed to determine the hemodynamic effects of 12-hour (12-h) shifts, and changes in blood pressure (BP) and heart rate variability (HRV) during 36 h rest time following 12-h shifts. Fifteen male shift workers with a mean age of 32.9 yr were recruited from a semiconductor factory. Ambulatory BP (AmBP) monitoring was performed for a total of 48 h for each participant. Six workers were monitored for 48 h by Holter electrocardiogram on both the day and night shifts. Paired self-comparison was used to estimate the difference between two hourly measurements of 12-h BP, HR, and HRV using the same timetable intra-individually. We also applied mixed models to estimate the effects of 12-h shifts on the delayed recovery of BP and heart rate (HR) in six workers who completed 96-h AmBP monitoring, including a 48-h night shift-rest period and another day shift period. Results showed that 12-h night shift work gave a persistently elevated systolic and diastolic BP (SBP and DBP) and HR, and decreased HRV compared to 12-h day shift work with the corresponding resting time. In addition, there was delayed SBP and DBP recovery on the first 12-h rest time in night shift workers, which was further demonstrated on the second 12-h rest time after adjustment for possible confounders through mixed models. In conclusion, 12-h night shift work may elevate BP and HR and decrease HRV. It is also associated with delayed BP recovery.
The effectiveness of Internet-based self-help programs for insomnia is still unclear. A randomized controlled trial was conducted to evaluate the effect of an Internet-based self-help program for better quality of sleep among adult workers. Forty-three volunteers were recruited and randomly assigned to either an intervention group (n=21) or a waiting-list group (n=22). The intervention group participated in a two-week Internet-based program, including selecting and daily practicing sleep-related target behaviors and monitoring those behaviors along with sleep quality. At the same time, each participant received automatically generated, personalized messages and reports both daily and weekly. A total of 12 intervention group participants and 18 waiting-list group participants completed questionnaires at baseline, post-intervention, and at a 3-wk follow-up. Subjective sleep quality was measured by a self-reported questionnaire developed for this study. The sleep quality score increased in the intervention group at post-intervention, with a significant interaction effect [F(1,28)=5.19, p=0.031]. Sleep-related behaviors also greatly increased in the intervention group at post-intervention, with a significant interaction effect [F(1,28)=7.14, p=0.012]. Sleep-onset latency reduced in the intervention group at follow-up, with a marginally significant effect [F(1,28)=3.52, p=0.071]. The Internet-based self-help program improves subjective sleep quality and sleep-onset latency among adult workers.
The purpose of this study was to assess the value and usefulness of high resolution computed tomography (HRCT) in the diagnostics of small opacities and complications of silicosis in mine machinery manufacturing workers, compared to conventional radiograms. The diagnosis of silicosis is mainly based on the radiological findings of workers exposed to the dust causing lung fibrosis. However, on radiograms many parenchymal structures overlap, which limits the sensitivity and specificity of the method. Difficulties in accurate interpretation of conventional radiograms in silicosis also result from their relatively low resolution. We randomly selected 30 I period silicosis patients from 77 I period silicosis patients working at a mine machinery manufacturing company. Out of 1078 non-silicosis and 162 0+ period silicosis subjects, 30 non-silicosis and 30 0+ period silicosis subjects were randomly selected and matched with the 30 I period silicosis subjects by age (± 3.0 yr) and occupational exposure time (± 2.0 yr). Chest X-rays were taken at maximal inspiration. For the HRCT examination, the GE Somatom plus apparatus was used. Eight, five and six subjects were respectively diagnosed as 0+, I or I+ period silicosis based on HRCT among 90 subjects whose original diagnoses were non-silicosis, 0+ or I period silicosis based on radiography. The numbers of small opacities in HRCT scans were significantly higher than those seen in radiography in all lung zones (p<0.01). HRCT was more sensitive than radiography in detecting small opacities of mid-out zones of the lung, but no statistical significance was found between the two methods in the detection of small opacities of lower zones of the lung. A statistically significant increase in the detectability of bulla, emphysema, pleural, mediastinal and hilar changes was observed (p<0.05). HRCT might be more sensitive than radiography in detecting lung parenchymal changes suggestive of silicosis.
This is the first paper on suicidal ideation and attempts among ambulance personnel. This study aimed to investigate levels of suicidal ideation and suicide attempts among ambulance personnel, and to identify important correlates and the factors to which ambulance personnel attribute their serious suicidal ideation. A comprehensive nationwide questionnaire survey of 1,180 operational ambulance personnel was conducted. Measurements included: Paykel's Suicidal Feelings in the General Population questionnaire, the Hospital Anxiety and Depression scale, the Subjective Health Complaints Questionnaire, the Maslach Burnout Inventory, the Job Satisfaction Scale, the Basic Character Inventory, and the Rosenberg Self-Esteem Scale. Lifetime prevalence ranged from 28% for feelings that life was not worth living to 10.4% for seriously considered suicide and 3.1% for a suicide attempt. Serious suicidal ideation was independently associated with job-related emotional exhaustion (feelings of being overextended and depleted of resources) (OR 1.5, 95% CI 1.1-2.0) and bullying at work (OR 1.7, 95% CI 1.02-2.7), younger age, not married/cohabitant, depression symptoms, low self-esteem and the personality trait reality weakness. In general, suicidal thoughts were hardly attributable to working conditions, since only 1.8% of ambulance personnel attributed suicidal ideation to work problems alone. In conclusion, ambulance personnel reported a moderate level of suicidal ideation and suicide attempts. Although serious suicidal ideation was rarely attributed to working conditions in general, this study suggests that job-related factors like emotional exhaustion and bullying may be of importance.
Solvents represent an important group of environmental pollutants to which people are exposed daily in the workplace. The physico chemical properties of solvents may result in disturbances to cellular structures, including damage to DNA. However, the effects of mixtures of solvents are not well known. Mutations caused by environmental agents are related to cancer development and other degenerative diseases. The work in a research laboratory that uses several types of solvents is equally predisposed to these hazards. In this study, we evaluated the mutagenicity of urine from 29 subjects exposed occupationally to solvents in a chemistry research laboratory and 29 subjects without occupational exposure (controls). Urine samples were collected in polyethylene containers at the end of the work shift. For the concentration and extraction of urine samples the XAD-2 resin was used with acetone as an eluting agent. Several strains of Salmonella typhimurium (TA100, TA98, TA97a, TA1535, YG1024) should be used to assess mutagenic susceptibilities among workers exposed to organic solvents. Different doses of extract (1.5; 3.0; 6.0 and 12.0 ml equivalents of urine per plate) were tested on S. typhimurium strains TA100 and YG1024, with and without metabolic activation. The mutagenic activity, measured in Salmonella typhimurium YG1024 with S9 mix, was significantly greater in urine from workers than from controls (p≤0.05). These results indicate the relevance of using biomarkers to assess the risk of occupational exposure to organic solvents.