[A study on occupational peripheral nerve disorders: a general view].

OBJECTIVES: The studies on occupational peripheral nerve disorders (OPD) in the workplace and future issues of OPD were overviewed based on the author's experiences. METHODS: The author shows four case studies because of four chemicals; cross-sectional studies using nerve conduction velocity (NCV) on the effect on the peripheral nerve among workers exposed to carbon disulphide (CS2) in rayon manufacturing factories and studies on OPD among patients with vibration syndrome (VS) and non-specific cervicobrachial disorders (CBD). RESULTS: Four cases of OPD due to chronic poisoning because of inorganic lead, thallium, n-hexane, and methyl bromide, respectively, were presented with clinical signs and symptoms of OPD and the cause-and-effect relationships were described. Cross-sectional epidemiological studies clarified that workers exposed to approximately 5 ppm of CS2 showed NCV reduction in the lower extremities and those exposed to > 5 ppm showed NCV reduction in the upper extremities. Multifocal damages due to VS was presented through high rate of patients with sensory nerve conduction velocity (SCV) reduction in multiple nerves. SCV reduction of the radial nerve in the index finger among patients with CBD was presented. CONCLUSIONS: The various OPD phases were shown by case, patient, and epidemiological study. However, the recent decrease of work-related illness due to chemicals may result to OPD reduction. The issue of OPD including other factors and differential diagnosis, will remain eventually owing to introducing chemicals of which toxicity are unclear.

A case of cervico-brachial disorder due to tactile interpretation for deaf-blind persons.

OBJECTIVES: We herein report a case of cervico-brachial disorder (CBD) due to long-term tactile interpreting. METHODS: The patient was interviewed to investigate her past history, occupational history, work conditions and clinical course in detail. The case was diagnosed in accordance with the "Diagnostic Criteria for CBD 2007" established by the Research Association for CBD of the Japanese Society for Occupational Health. RESULTS: The patient was a 49-year-old female who has worked as a regular occupational instructor at a welfare work activity center for deaf people since April 22, 2010. Her primary job is to instruct and aid others in learning confectionery manufacturing and coffee shop tasks. She also performs tactile interpreting for two deaf-blind workers during a morning health check and during any meetings. On September 3, 2010, she interpreted by tactile signing for about three hours alone during a meeting, due to the absence of other interpreters. She developed severe pain in her back immediately after carrying out this interpretation, and the pain thereafter continued and developed in the upper extremities. She was diagnosed with a severe and prolonged case of the non-specific type of CBD. DISCUSSION: Interpretation by tactile signing may impose a heavier burden on the upper extremities, shoulders and neck than that imposed by common sign language. A shorter time of interpretation, ensuring the availability of rest time and supporting tools or methods for the upper extremities, are therefore considered to be necessary to prevent the incidence of CBD among interpreters using tactile signing.

[Clinical findings of the patients with sick building syndrome and the results of environmental measurement].

OBJECTIVES: Although many survey reports on sick house syndrome have been published, few clinical studies have reported sick building syndrome (SBS) in Japan. We examined patients with SBS-like complaints by clinical observation and made environment measurements. METHODS: The subjects of our study were 11 office workers (2 men and 9 women) who visited our hospital because of poor physical condition after the construction and painting of a fireproof vault in their office. We performed a medical interview, biochemical examinations of blood, immunological tests, pulmonary function tests, and psychological tests. The environment in the office was evaluated 3 times at 27, 55, and 132 days after the cessation of vault construction. A questionnaire survey was distributed to the workers who did not visit our hospital. RESULTS: The workers resumed work 9 days after the end of construction: Shortly after the resumption of work, most of the workers smelled a bad odor, and complained of headache, malaise, disturbed concentration, and eye irritation. Acrylic resin paint was used for painting the vault, and the concentrations of toluene, xylene, and total volatile organic compounds (T-VOC) on day 27 after painting were 2,972, 2,610, and 7,100 µg/m³, respectively. One hundred and thirty-two days after painting, the concentrations of toluene, xylene, and T-VOC decreased to unscented levels of 78, 113, and 261 µg/m³, respectively. CONCLUSION: Seven females among the eleven patients were diagnosed as having SBS on the basis of the time of the onset of the symptoms, negative results of allergy and other organic diseases, and the results of the environment measurements. From the responses of the other workers (22 men and 1 woman) to the survey questionnaire, the development and the disappearance of complaints, such as bad odor and unpleasantness, agreed with change of the level of toluene in the vault, which confirmed the validity of the SBS diagnosis.

Musculoskeletal pain and night-shift naps in nursing home care workers.

BACKGROUND: Care workers in nursing homes are at high risk of developing musculoskeletal disorders (MSDs). Many care workers work in shifts, which may compromise both the quality of care they give and their working life. Taking a nap during night shifts has been proposed to ameliorate shift work-related problems, but its relationship with MSDs is not clear. AIMS: To explore how MSD pain differs according to frequency of night-shift naps. METHODS: A questionnaire study was conducted on 111 care workers at three nursing homes. Of 98 respondents, data from 66 shift workers (54 women) were analysed. Data on self-rated pain in multiple sites (neck, shoulder, arm, leg and low back), naps during night shifts and relevant variables were collected. Participants were categorized into three groups on the basis of frequency of night-shift naps taken during the previous month: non-nappers, <50% nappers and >or =50% nappers. RESULTS: Pain at all sites, with the exception of low back pain, differed significantly among the three groups. Pain scores were lowest at the arm and leg for the > or =50% nappers. Neck and shoulder pain was lower for the > or =50% nappers and the non-nappers compared to the <50% nappers. CONCLUSIONS: Reduced pain in the arm and leg was associated with taking a nap at least once every two night shifts among the nursing home care workers. No association was found between low back pain and night-shift naps in this sample.

Visually-evoked P300 and NOGO potentials as indicators of central nervous system function in patients with vibration syndrome.

OBJECTIVE: The present study aimed at clarifying the effects of vibration syndrome (VS) on recognition, memory, and selective attention as well as suppression of hand movement in the central nervous system (CNS). METHODS: Sixty-four patients with VS due to previous exposure to vibration from chain-saw work (Ch) or rock drilling work (RD) and 53 age-matched controls were examined for visually evoked P300 (V-P300) and NOGO potentials (NOGO-P). The patient group was divided into two subgroups, one with VS due to Ch work (Ch group, N = 17) and the other with VS due to RD work (RD group, N = 44). RESULTS: ANOVA of latencies of V-P300 between three groups including two subgroups by vibration tools and controls was significant (P < 0.001), with significant difference between the control and RD subgroup (P < 0.001) and between the Ch and RD subgroups (P < 0.001). ANOVA of V-P300 amplitude was also significant (P < 0.001), with significant difference between the control group and RD subgroup (P = 0.042). NOGO-P was recorded in 28 of 37 controls (75.7%). Latencies of NOGO-P among VS patients were significantly delayed compared with those of controls (P = 0.0152). The proportions of subjects with abnormal values of V-P300 and NOGO-P among VS patients and RD operators were significantly higher than those in the control. CONCLUSION: These findings suggest that VS affects CNS function as represented by V-P300 and NOGO-P.

Work schedule differences in sleep problems of nursing home caregivers.

Nursing home caregivers (n=775; 604 women; mean age 33.6 years) were studied to examine how work schedules affect their sleep. The shift group (n=536) worked under a rotating two-shift system (n=365), a rotating three-shift system (n=66), or other types of shifts (n=78). The non-shift group included 222 caregivers. Participants completed a questionnaire about working conditions, sleep problems, health, lifestyle, and demographic factors. The two-shift caregivers reported the highest levels of difficulty initiating sleep (DIS, 37.6%), insomnia symptoms (43.0%), and poor quality of sleep (24.9%) among the groups. Adjusted odds ratios for these problems were significantly greater for the two-shift caregivers than for non-shift counterparts: DIS (odds ratio 2.86, 95% confidence interval 1.57-5.20), insomnia symptoms (2.33, 1.36-4.02), and poor sleep quality (2.15, 1.09-4.22). Our data suggest that working under a rotating two-shift system, which has a longer night shift, is associated with an elevated risk of sleep problems for nursing home caregivers.

[Usage survey of care equipment in care service facilities for the elderly].

Musculoskeletal disorders(MSD)have been increasing recently among care workers. Since providing care workers with appropriate equipment is effective for preventing MSD, we conducted a questionnaire survey in two nursing homes and a healthcare facility for the elderly to clarify equipment usage, problems and points for improvement. A total of 81 care workers(average age 32.2 yr; 63 females, 18 males)participated in the survey. The average number of residents and the average resident's care level were 70.0 and 3.6, respectively. Wheelchair and height adjustable beds were fully available and always used in all facilities. Portable lifts, ceiling lifts and transfer boards were, however, few in all 3 facilities and the proportion of use was 14.8%, 16.0%, and 23.5%, respectively. Participants reported that it is time consuming to move residents from place to place with lifts and there is a danger of dropping a resident. Although approximately 90% of care workers had received education and training on care techniques, the workload on the low back was found to be great. Therefore, we thought that care workers must consistently use care equipment. To achieve such increased usage, we must improve the usability of the equipment.

Development and process evaluation of the participatory and action-oriented empowerment model facilitated by occupational health nurses for workplace health promotion in small and medium-sized enterprises.

The objective of this study is to develop an available empowerment model for workplace health promotion (WHP) in small and medium-sized enterprises (SMEs) and to evaluate its applicability and feasibility. Semi-structured interviews with employers and workers in SMEs were conducted to assess their actual requirements for support. The structure of our new empowerment model was discussed and established through several rounds of focus group meetings with occupational safety and health researchers and practitioners on the basis of results of our interviews. We developed a new participatory and action-oriented empowerment model based on needs for support of employers and workers in SMEs. This new model consists of three originally developed tools: an action checklist, an information guidebook, and a book of good practices. As the facilitators, occupational health nurses (OHNs) from health insurance associations were trained to empower employers and workers using these tools. Approximately 80 SMEs (with less than 300 employees) were invited to participate in the model project. With these tools and continued empowerment by OHNs, employers and workers were able to smoothly work on WHP. This newly developed participatory and action-oriented empowerment model that was facilitated by trained OHNs appears to be both applicable and feasible for WHP in SMEs in Japan.

Sensory nerve conduction velocities of median, ulnar and radial nerves in patients with vibration syndrome.

OBJECTIVE: The present study aimed to clarify the range of involvement for hand-arm vibration syndrome (VS) in the median, ulnar and radial nerves of the hand. METHODS: Sensory nerve conduction velocities (SCVs) for 3 nerves in the hands and arms were examined for 34 patients with VS and 23 age-matched controls. Neuropathy types were classified by possible carpal tunnel syndrome (CTS), Guyon's syndrome and digital neuropathy in three nerves. RESULTS: SCV in the median nerve (middle finger, wrist-elbow) and ulnar nerve (little finger, wrist-elbow), and amplitudes of the median nerve (wrist-proximal and distal parts of the middle finger), ulnar nerve (wrist-proximal and distal parts of the little finger; forearm-proximal part of the little finger; upper arm-proximal part of the little finger) and radial nerve (dorsal side of the hand-thumb) were significantly reduced in VS patients compared with controls. According to subject classifications based on the results of SCV and amplitude of nerve action potential, 52.9% of VS patients displayed multi-focal neuropathy including digital neuropathy, possible CTS and/or Guyon's syndrome. CONCLUSION: These findings suggest that VS affects all three nerves in the hand. According to classification results, the main disorders of peripheral nerves comprise digital neuropathy.

Relationship between blood lead level and work related factors using the NIIH questionnaire system.

Over an 11-yr period (1990-2000), a questionnaire survey on work environmental management and environmental improvement was conducted on 259 lead-handling factories and 7,623 subjects. Labour Inspection Offices identified these factories as requiring environmental improvement, or possessing a desire to improve their working environment. We analyzed factors affecting blood lead levels (PbBs). These factors were gender, age, employment duration, factory size, work environment control (WEC) class, and job categories. The PbB of men was found to be higher than that of women, and may be due to the differences in job distribution. PbB increased along with increasing age and employment duration. PbB declined as the factory size increased. The odds ratio (OR) of PbB higher than 20 microg/dl according to factory size was significantly high even after adjusting for WEC class. This demonstrates that not only the working environment but also safety management was poorer among small-scale factories that large-scale factories. The rise of PbB along with the increase of WEC class confirmed that the results of work environment measurement are correlated with individual exposure levels. The risk of having a 20 microg/dl or higher PbB was different for various lead handling jobs. Smelting or refining lead had the highest risk for lead exposure while painting or baking had the lowest risk. As our study population was not a randomly selected sample, we are unable to generalize our results for workers across Japan. However, we were able to indicate which jobs pose a high-risk and the effectiveness of using the work environment control class as an index of worksite environment levels.

Arm pain and daytime sleepiness among nursing home employees.

We investigated the relationship between musculoskeletal disorders and sleep problems among 98 employees (79 women) at three nursing homes. Self-reported data were collected regarding pain in the neck, shoulders, arms, legs, and low back, sleep disturbances, daytime sleepiness (Epworth Sleepiness Scale), and the level of workload on the hands, legs, and low back by type of care. Pain in the arms was significantly associated with less difficulty initiating sleep, fewer symptoms of insomnia, and a higher level of daytime sleepiness. After adjusting for age and gender, only the association between arm pain and daytime sleepiness remained significant (Odds Ratio 6.70, 95% Confidence Interval 1.40-31.97). Participants with both arm pain and daytime sleepiness showed significantly greater levels of workload in some kinds of care in a systemic manner than counterparts without either complaint. These findings suggest that arm pain is associated with elevated sleep propensity/fatigue in nursing home work.

Development of multi-dimensional action checklist for promoting new approaches in participatory occupational safety and health in small and medium-sized enterprises.

To meet diversified health needs in workplaces, especially in developed countries, occupational safety and health (OSH) activities should be extended. The objective of this study is to develop a new multi-dimensional action checklist that can support employers and workers in understanding a wide range of OSH activities and to promote participation in OSH in small and medium-sized enterprises (SMEs). The general structure of and specific items in the new action checklist were discussed in a focus group meeting with OSH specialists based upon the results of a literature review and our previous interviews with company employers and workers. To assure practicality and validity, several sessions were held to elicit the opinions of company members and, as a result, modifications were made. The new multi-dimensional action checklist was finally formulated consisting of 6 core areas, 9 technical areas, and 61 essential items. Each item was linked to a suitable section in the information guidebook that we developed concomitantly with the action checklist. Combined usage of the action checklist with the information guidebook would provide easily comprehended information and practical support. Intervention studies using this newly developed action checklist will clarify the effectiveness of the new approach to OSH in SMEs.

Nationwide survey of occupational health activities in small-scale enterprises in Japan.

OBJECTIVES: In order to clarify the real condition of occupational health (OH) activities in small-scale enterprises (SSEs) at the nationwide level, we conducted a questionnaire study sent to SSEs. We selected SSEs according to their employee numbers published in the in "Census of Workplaces in 1999". SUBJECTS AND METHODS: About 2000 establishments were selected from the list in the "Census" describing the names and addresses of enterprises with 5 or more employees. The questionnaire included type of business, number of employees, independence, OH competent person, conduction of health examination, potential hazardous works and countermeasures (chemicals handling, computer work, etc), committee or other types of organizations for OH, and others. RESULTS: Two hundred eleven establishments with 1-4 employees, 779 establishments with 5-9 employees, 681 establishments with 10-49 employees, 300 establishments with 50-99 employees, and 57 establishments with more than 100 employees, a total of 2,029 establishments responded to the questionnaire. The types of businesses (the number of establishments) were construction (216 establishments), manufacturing (604), transportation and communication (216), wholesale and restaurants (390) and services (602). The rate of independent enterprises was 54.1% and branches 45.9%. Indicators of OH activities including selection of OH competent person, enforcement of OH guideline for computer work, OH education about the occupational health risks, enforcement of special health examinations and general health examinations in SSEs with 1-4 and 5-9 employees were worse than SSEs with 10 or more employees. CONCLUSIONS: The differences of OH activities by scale of number of employees were clarified at a nationwide level. However, OH activities in SSEs with 1-4 employees were not clarified sufficiently. Various policies and methods should be established and implemented to improve the low level of OH activities in SSEs.

[Status of noise in small-scale factories having press machines and hearing loss in workers].

A study on noise and hearing loss was conducted in 36 small-scale factories where press machinery is actively used. Noise levels in working environments were measured in 34 factories. Of those measured, two (6%), eight (24%) and 24 (71%) factories were classified into control classes I, II and III, respectively, according to guidelines established for the prevention of noise-related disorders. Furthermore, personal exposure levels to noise were measured for 23 workers. Twenty-one (91%) of those workers measured were exposed to 85 dB(A) or higher, (the occupational exposure limit for an 8-hour exposure period). Maximum exposure levels were found to be at 102 dB (A). Hearing tests were then conducted on 97 male workers at those 36 factory sites. Twenty (21%), 30 (31%) and 10 (10%) of the workers measured were classified into a "precursory symptom group", a "slight hearing loss group" and a "medium to serious hearing loss group", respectively, based on the aforementioned guidelines. It was found that as workers' ages increased, the percentage of workers having some degree of hearing loss increased. Specifically, it was found that there was some level of hearing loss for 93% of those studied aged in their 50's, and up to 100% in those aged in their 60's.

Neuro-physiological study in persons with cervico-brachial disorders.

OBJECTIVES: In order to clarify the involvement in the nervous system by cervico-brachial disorders (CBD), we performed neurophysiological tests on the peripheral nervous system (PNS) and the central nervous system (CNS) in patients with CBD, subclinicals and healthy controls. SUBJECTS AND METHODS: We employed antidromic sensory nerve conduction velocities (SCV) in the hands and fingers for PNS function and event-related potentials (P300) for CNS higher function. Subjects for SCV were 27 patients, 14 workers with sign and symptoms of CBD (subclinicals) and 22 controls. Subjects for P300 were 23 patients, 12 subclinicals and 10 healthy controls. CONCLUSIONS: In the PNS, since significant reduction SCV in the index finger among patients was observed, we could not find clear evidence of decrease of conduction function. In the CNS, since the latencies and amplitudes of auditory P300 among patients were significantly delayed and decreased, respectively, and the latencies significantly correlated with symptom score, it was suggested that the dysfunction of the cognition and memory function. However, further investigation is necessary to clarify the mechanism.

Impaired manual dexterity and neuromuscular dysfunction in patients with hand-arm vibration syndrome.

Manual dexterity and hand functional difficulties in daily life in hand-arm vibration syndrome (HAVS) were investigated in 29 male patients with HAVS and 30 male controls without occupational exposure to hand-arm vibration. Manual dexterity was assessed by measuring the performance time of picking up and transferring 30 red beans, one by one, from one plate to another. Vibrotactile perception thresholds at 125 Hz and grip strength were also examined. Hand functional difficulties in daily life were surveyed with a questionnaire. The HAVS patients had an increased vibrotactile threshold, decreased grip strength, and low performance in transferring beans. Low performances with transfer times over 53 s (2SD from the mean in the controls) were found in 66% of the HAVS patients and 3% of the controls. Bean transfer times in the patients were correlated with an increasing vibrotactile threshold and decreasing grip strength. The transfer times of the patients were also associated with hand functional difficulties such as picking up coins, turning the pages of a newspaper, buttoning clothes, and pouring from a teapot. The patients with a prolonged transfer time over 60 s (3SD from the mean in the controls) were most likely to have hand functional difficulties. The present findings suggest that measurement of the bean transfer time will serve to assess manual dexterity among HAVS patients, and that impaired manual dexterity in patients may be associated with impaired sensory feedback and muscular dysfunction in the fingers and hands.

A study on the effect of lead on event-related potentials among lead-exposed workers.

OBJECTIVES: In order to clarify the effect of lead on higher cerebral functions, lead-exposed workers (Pb group) and controls were examined for event-related potentials. SUBJECTS AND METHODS: Fourteen lead-exposed workers with a mean age of 57.1 yr (SD=4.27, range 48-64; lead concentration of whole blood ranged from 33 to 106 microg/dl with a mean of 58.6 and SD 28.6 microg/dl) and 19 age-matched control workers with a mean age of 57.3 yr (SD=4.80, range 48-65) were examined. Visual P300 was recorded by button pushing to the target image (minute checkerboard pattern, 20%), and the NO-GO potential by no button pushing to the target image (same as above, 50%). RESULTS: Latencies of P300 in the Pb group (475+/-46.0 ms) were significantly delayed compared with those in controls (407+/-42.4 ms, p<0.01 by Student's t test). Amplitudes of the NO-GO potential in the Pb group (4.59+/-2.04 microV) significantly increased compared with those in the controls (3.18+/-1.41 microV, p<0.05). CONCLUSION: The finding suggests that lead exposure affects high cerebral functions of cognition and attention, but is unclear in suppression of movement.

Autonomic nervous activity during hand immersion in cold water in patients with vibration-induced white finger.

Autonomic nervous function in response to cold was investigated in 21 patients with vibration-induced white finger (VWF) and 17 healthy controls of similar age, using power spectral analysis of heart rate variability. In a supine position, electrocardiogram and skin temperature of both index fingers were measured during immersion of right hand in cold water at 10 degrees C for 10 minutes. Autonomic nervous activity was evaluated from the power of the low-frequency component (LF: 0.02-0.15 Hz), the high-frequency component (HF: 0.15-0.40 Hz) and the ratio of the LF to the HF power (LF/HF ratio). The LF/HF ratio, an index of sympathetic nervous activity, significantly increased during the immersion in the VWF patients, but did not significantly increase in the controls. The LF/HF ratio was then significantly greater in the patients than in the controls during the first 1-2 minutes of the immersion. The HF power related to parasympathetic nervous activity did not change significantly in either group. Finger skin temperature of the immersed right hand was significantly lower in the VWF patients than in the controls during the last five minutes of the immersion and in the recovery period. The present results indicate that sympathetic nervous response to cold is significantly enhanced in VWF patients. The exaggerated sympathetic response to cold in these patients is considered to contribute to the enhanced vasoconstriction of their extremities.

Reduced sensory nerve conduction velocity of the distal part of the radial nerve among patients with vibration syndrome.

The present study was aimed at clarifying the effects of vibration syndrome (VS) on the distal part of the radial nerve, which is rarely affected by chronic entrapment. Thirty-one patients with VS due to previous exposure to vibration and 18 age-matched controls were examined for sensory nerve conduction velocities in the distal part of the radial nerve (SCV-DR) in the dorsal side of the hand. The patient group was divided into two subgroups, one of those with vibration-induced white finger (VWF) in the thumb or index finger where sensory nerves are innervated by the radial nerve (N = 21) and the other without VWF (N = 10). SCV-DR among the patients was significantly slower than in the controls (t = 3.55, p = 0.00138). The ANOVA of SCV-DR for the three groups showed F2, 46 = 5.25 (p = 0.0088). A significant difference was found between the controls and the VWF (+) group (p = 0.0233), but not between the controls and the VWF (-) group (p = 0.478) by multiple comparison using Scheffe's method. These findings suggest that VS affects the radial nerve with a direct vibration effect and/or a co-operative effect with direct circulatory disturbance manifested by VWF.