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This study examined a cross-sectional association between self-reported low back pain (LBP) and unemployment among working-age people, and estimated the impact of self-reported LBP on unemployment. We used anonymized data from a nationally representative survey (24,854 men and 26,549 women aged 20–64 years). The generalized estimating equations of the multivariable Poisson regression models stratified by gender were used to estimate the adjusted prevalence ratio (PR) and 95% confidence interval (CI) for unemployment. The population attributable fraction (PAF) was calculated using Levin’s method, with the substitution method for 95% CI estimation. The prevalence of self-reported LBP was 9.0% in men and 11.1% in women. The prevalence of unemployment was 9.3% in men and 31.7% in women. After adjusting for age, socio-economic status, lifestyle habits, and comorbidities, the PR (95% CI) for the unemployment of the LBP group was 1.32 (1.19–1.47) in men and 1.01 (0.96–1.07) in women, compared with the respective non-LBP group. The PAF (95% CI) of unemployment associated with self-reported LBP was 2.8% (1.6%, 4.2%) in men. Because the total population of Japanese men aged 20–64 in 2013 was 36,851 thousand, it was estimated that unemployment in 1037 thousand of the Japanese male working population was LBP-related.

OBJECTIVES The aims of this study were to clarify in detail the levels of whole-body vibration (WBV) exposure from a variety of agricultural machines in a rice farmer over one year, and to evaluate the daily level of exposure compared with European and Japanese threshold limits. METHODS The subject was a full-time, male rice farmer. We measured vibration accelerations on the seat pan and at the seat base of four tractors with various implements attached, one rice-planting machine, two combine harvesters, produced by the same manufacturer, and one truck used for transportation of agricultural machines. The position and velocity of the machines were recorded in parallel with WBV measurements. In addition, during the year starting in April 2010, the subject completed a questionnaire regarding his work (date, place, content, hours worked, machines used). We calculated the daily exposure to WBV, A(8), on all the days on which the subject used the agricultural machines. RESULTS The WBV magnitude in farm fields was relatively high during tasks with high velocity and heavy mechanical load on the machine, and had no dominant axis. The subject worked for 159 days using the agricultural machines during the year, and the proportion of days on which A(8) values exceeded the thresholds was 90% for the Japan occupational exposure limit and 24% for the EU exposure action value. CONCLUSIONS Our findings emphasize the need for rice farmers to have health management strategies suited to the farming seasons and measures to reduce WBV exposure during each farm task.

Objective: The purpose of this study was to reduce the workload on the computer operator using the toes. Methods: A subject was a 22-years-old man with upper extremity impairments, who worked at a welfare work activity center. The actual duration of computer operation using the keyboard and touch-pad on the desktop was approximately four hours a day. The subject complained of low back pain and lower extremity fatigue at closing time. To alleviate physical load, the working environment was modified as follows. The installation position of the keyboard and touch-pad was moved to the floor. The computer monitor was moved up and close to the operator. A new monitor, a video camera and light aimed at the keyboard were set up for keyboard projection. The effect of this modification was evaluated by a posture analysis, a sitting pressure distribution, a surface electromyogram at the neck and low back, and subjective feelings of the physical load. Results: In accordance with the working environmental modifications, the posture, the sitting pressure distribution, the myoelectric potential, and the physical load of the user improved. Conclusion: Environmental modifications can improve pain and fatigue at closing time and the operability of the computer user.

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.

In our previous study, we elicited effectual points of view (POV) in occupational health management for visual display terminals (VDT) operators with disabilities. In order to validate the POV, two VDT operators with cerebral palsy newly-participated in our case study. Problems were ascertained, and in order to attempt to reduce the workload and improve operability, we performed intervention using ergonomic measures. Evaluations were conducted through observations of the equipment used and posture, as well as measurements of sitting pressure distribution and surface electromyogram. For Case 1 (a 33 yr-old male), a trunk support was introduced inside the armrest of his chair to maintain the trunk in a comfortable position. For Case 2 (a 21 yr-old female), in order to improve her unstable sitting position, we changed her chair and adjusted it to an appropriate desk height. For both cases, we confirmed improvements in posture, sitting pressure distribution, myoelectric potential or operability. We were able to confirm that "maintaining of a comfortable trunk" and "alleviation of excessive bending, extension, and curvature of the spinal column and joints" obtained from the previous study as POV in health management are also effective in the present interventional cases.

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.

In order to ascertain the workload and lifestyle of medical residents prior to the introduction of a new medical resident training system, 102 residents at a national university hospital were monitored for four consecutive weeks to ascertain their life habits. Valid responses were obtained from 76% of the respondents for a total of 2,722 person days. It was found that the average length of sleep was 5.7 h on weekdays and 6.8 h on weekends. Of the 102 residents, 40% slept less than six hours a night and 17% slept less than five hours a night. The time spent sleeping was particularly short among surgical residents. Given that lack of sleep not only affects the health of the residents negatively, but also compromises the safety of medical care that they provide, the new medical residency training system will need to monitor and analyze the wellbeing, including sleep patterns, of medical residents.

The purpose of this study is to ascertain the incidence of cervicobrachial muscle tension induced by voice among sign language interpreters (SLIs). The analyzed subjects included 8 professional SLIs (Case group) who complained of pain in the cervicobrachial muscle when listening to others' talking and 8 other people who have not learned sign language (Control group). Matching sexes, ages, and smoking habits of the Case and the Control groups was carried out. Informed consent to participate in the study was obtained from all subjects. While subjects relaxed in a sitting position, surface electromyographies (EMGs) were recorded from the right and left trapezius muscles and biceps brachii muscles. During this time, all subjects had two listening tasks: to listen to lectures in Japanese and to listen to instrumental music. An inquiry about subjective symptoms was conducted just after each task. Root-mean-square (RMS) values per 100 ms in each of the tasks were calculated for analysis of surface EMG. An original criterion of judgment was that the threshold of RMS values was 3.8 microV, and its threshold continued for more than 1 s. The criterion was used and the muscle tension was confirmed. Results showed muscle tension in the trapezius muscles or the biceps brachii muscles among 5 of 8 subjects in the Case group, and in 1 of 8 in the Control group when listening to the lecture. 3 subjects in the Case group and none in the Control group showed muscle tension in the trapezius muscles when listening not to music but to the lecture. The differences between the Case and Control groups in these results were not statistically significant. Confirmed muscle tension in SLIs when listening to a Japanese lecture is probably induced by the Japanese voice. It is necessary to further investigate whether muscle tension is an acquired reaction from sign language interpreting or a pathological reaction. Listening to Japanese voices may contribute to muscular overload in SLIs so that it may be necessary for SLIs to relax their muscles during break times with an absence of Japanese voices.

滋賀県での農作業災害予防のための課題を明らかにする目的で, 県共済連の保険請求資料を基に, 1982年から1991年までの期間について, 主な農業機械を原因とした災害の発生実態を経年的に検討した。農作業災害は調査期間中に男性に914件, 女性に288件発生しており, 1983年が144件で最も多く, 以後, 年間100件程度で推移していた。災害発生に結びついた主な農業機械は, コンバイン, 草刈機, トラクター, 耕転機であった。コンバイン, トラクター, 耕転機による災害は, 減少ないしは横這いであったが, 草刈機による災害は増加していた。1989年以後, 60歳以上の年齢階層が被災者の中で最も高い構1成比であり, しかも, それは滋賀県の農業従事者の60歳以上構成比よりも高かった。コンバイン, トラクターでは, 機械の操作性や作業環境に起因する災害は減少していたが, 脱穀や耕転作業時の災害は減少していなかった。草刈機による災害増加には, 普及台数の増加や傾斜畦畔の拡大により使用頻度が増えたことが関与していることが考えられた。草刈機による災害予防のためには, 機械や作業環境の改善とともに保護具の導入が必要と考えられた。

According to the recent changes of working environments and socio-economical conditions, the proportion of working women are increasing in Japan. Characteristics of occupational workload and stress of Japanese working women are consistent with those in many industrialized countries except man-dominant culture. In this review we describe the history, current issues, and future research directions on occupational health of working women, especially focused on reproductive health, work-related musculo-skeletal disorders (WMSDs), and mental disorders. In the reproductive health survey, traditionally main concern was about pregnancy outcomes, then fecundity studies, such as time to pregnancy, became topics recently. Future research will be shifted to outcomes not only during pregnancy but also disorders of hormonal balance and climacterium or health conditions after menopause. WMSDs are reviewed on mainly gender difference and its causative factors. Historically, mental health of working women in Japan has focused on the job stress of nurses. We compare results with a lot of recent researches in Europe and U.S.A., where interaction between occupational stress and family roles were studied. It is not easy to predict the prospective status of female workers in Japan, but social, workplace and familial supports will enhance their health promotion.

The Cinderella hypothesis postulates the continuous activity of specific motor units during low-level muscle contraction and contradicts the concept of motor-unit substitution. Constant trapezius muscle activity has been reported in typical visual-display-unit-related tasks. If it can be shown that constant muscle activity can be caused by the continuous firing of single motor units, this could explain the frequent complaints of muscular neck pain reported by computer users. The present study was undertaken to investigate motor-unit activity in the trapezius muscle during resting with closed eyes, while inputting three-digit numbers with auditory presentation at a rate of 0.5 Hz, and while tapping on a key with the right index finger at a rate of 5 Hz. Electrodes with four fine wires were inserted into the right upper trapezius muscle of six healthy subjects, and three-channel intramuscular electromyography was recorded. The decomposition programme MAPQuest, developed to analyse short-term one-channel signals, was complemented with MAPView, a programme that merges the short-term results of 10 s to a 3-min analysis. The results showed that activity in the trapezius muscle was induced in one subject while resting, in two subjects while inputting data, and in five subjects while finger tapping. Long-lasting single motor-unit firing was observed in two subjects while inputting data and in one subject while finger tapping. Whilst our findings may support the Cinderella hypothesis, the measurement periods are too short to confirm it fully, and for further discussion it is necessary to record and analyse for longer periods.

The authors' study in 1983 revealed that the whole-body vibration of the tractor units of freight containers was most hazardous in the back-to-chest directions (x-axis). The allowable exposure time was considerably shorter than that for heavy duty trucks. The low back pain (LBP) among the drivers seemed to be due to the long working hours and the ergonomically unsound tractor design, as well as the vibration. A preventative measure was the introduction of a tractor cab suspended by an air spring instead of a steel spring. In 1992, a follow-up field study was conducted. A personal vibration exposure meter developed by us measured the whole-body vibration on eight tractors. Eighty-nine triplets matched with the age and the years of driving tractors answered a questionnaire evaluation of the ergonomics of their tractor units. The comparison of the newest steel suspension vehicles to the old ones produced by the same motor company revealed that in thex-axis the vibration level had decreased by as much as 4 to 9 dB. Some tractors showed an increase in vibration in the buttocks-to-head direction (z-axis). However, such adverse changes seemed not to affect evaluations according to the fatigue-decreased proficiency boundary (FDP) and the exposure limit (EL) recommended in ISO 2631–1978. The present models, regardless of the type of suspension, changed the direction of the most hazardous vibration from thex-axis to thez-axis. However, the effect of the air-suspension was not so remarkable as expected. Among 40% of drivers seemed to exceed the FDP boundary during a day. The questionnaire study showed an improvement in the ergonomic evaluation of the tractors. The air suspension models seemed to induce less LBP than the steel suspension models.

A field study designed to reveal the physiological workload on garbage collectors (GC) was conducted in Japan. Three drivers who only operated a garbage truck, three loaders who actually collected as a team, three solo collectors, and one clerical worker, totaling 10 male workers participated in this study. The ambient temperature and the relative humidity, activity intensity, and heart rate were measured on the three days in July. The mean heart rate of the workers, excluding the clerical worker, was 97.5 bpm. There were cases in which the heart rate limit, as defined by ACGIH, was exceeded, including a case in which the loader sustainably exceeded this limit for over an hour. There were 10 worker-days in which the 58%HRmax level (corresponding to the permissible limit specified in the Netherlands) was exceeded based on the findings of the 18 worker-days for the loaders and solo collectors. There were many cases in which the energetic load of GC in the humid summertime in Japan exceeded the permissible limits as established in the U.S.A. and the Netherlands. The careful inspection of the actual work conditions and improvements in the work environment should be implemented for the occupational safety and health of GC.

滋賀県湖北地区の菊栽培農家20人に対して,「かぶれ」症状と菊栽培に関する聞き取り調査と皮膚科学的検診を行った。菊栽培以後「かぶれ」を経験しているものは13人おり, その内8人は菊栽培以後初めて「かぶれ」を経験していた。「かぶれ」との関係のある菊栽培作業としては,「下葉取り」や「収穫」・「出荷調整」作業等, 菊との接触が濃厚な作業が指摘されていた。パッチテストの結果は, 20人中13人が菊あるいは農薬に陽性であった。菊栽培以後「かぶれ」を経験している13人については, 10人が菊あるいは農薬に陽性であった。一方,「かぶれ」の原因としては菊より農薬を挙げるものが多く, 菊栽培作業では農薬散布時ほど服装や汚染予防に注意が払われていなかった。その原因としては, 農薬の危険性に関する教育は行われても, 菊と接触皮膚炎との関連については教育が行われていなかった。菊栽培農家の接触皮膚炎予防のためには栽培当初からの衛生教育と営農形態や作業態様に則した具体的な防護方法の指導が必要と考えられた。

This study aimed to examine the status of time spent working and sleeping by resident doctors before the introduction of the New Training System for Residents in Japan. A time-budget survey was conducted over a 4-wk period on 102 residents at the Shiga University of Medical Science Hospital, and the response rate among residents was 76% of a total of 2,722 person-days. The average number of hours spent sleeping was the lowest and spent in the hospital including commuting time was the highest in residents of the surgery department, at 4.4 h and 18.9 h, respectively. Forty percent of residents reported dozing off at work, with the incidence rate being highest in residents of the surgery department (0.7 times/person-day). Dozing appeared to occur in response to the lack of sleep and fatigue, since the same residents slept longer on nights before days they reported not dozing off than on nights before days when they did doze off. Strong correlations were observed between the number of sleeping and working hours and between working hours and the number of patients in a resident's care. In order to maintain high standards of training and to get sufficient sleep it is therefore necessary for residents to manage their work and the number of patients in their care.

We examined the effect of mental stress on hemoglobin concentrations in the trapezius muscles of 20 healthy, non-smoking women. The participants held their arms out horizontally (physical stimulus) while standing upright for 1 min with 5 min intervals of seated rest, or performed Stroop's Color Word Test (mental stimulus), or both simultaneously. We measured heart rate, muscle tissue hemoglobin (oxy-hemoglobin, OxyHb; deoxy-hemoglobin, DeoHb; total hemoglobin, TotHb) concentrations in, and obtained surface electromyograms from the right upper trapezius muscle. Changes in the hemoglobin concentration (DeltaOxyHb, DeltaDeoHb, DeltaTotHb) induced by physical and/or mental stimuli were calculated. Changes with physical stimulus alone were compared with those induced by physical plus mental stimuli using repeated measures ANOVA. The DeltaDeoHb with physical and mental stimuli was significantly lower (p=0.013) than that with the physical stimulus alone, whereas the DeltaOxyHb and the DeltaTotHb values did not significantly differ (p=0.281, p=0.230). This finding indicates that mental load affects DeltaDeoHb in the trapezius muscle. We think that mental stimulus might provoke a reduction in oxygen consumption by the trapezius muscle. Further investigations using a longer duration of physical and mental stimuli are required.

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.

Many forklift drivers have musculoskeletal disorders such as low back pain related to poor work posture and whole-body vibration. With a forklift operator's seat capable of 45-degree swiveling, we evaluated the physical reduction in the load in 10 subjects working in a back-looking position by means of surface electromyography (EMG) and the angle of rotation of the trunk and neck regions. The amplitude of surface EMG on the trapezius, erector spinae, and latissimus dorsi muscles in looking back or maintaining a back-looking position decreased with a swiveling seat compared to the stationary seat. Nevertheless, there was little alleviation of the amplitude of surface EMG on the sternocleidomastoid muscle in maintaining a back-looking posture and no decrease in looking back. The angle of rotation of the trunk maintaining a back-looking position was decreased greatly with the swiveling seat, but no decrease in the rotation angle of the neck was seen. Our study suggests that a swiveling seat is effective in reducing the physical load on the forklift driver during back-looking operations, and this may lead to the prevention of low back pain.

We took the blood pressure and ECG of 8 male truck drivers who drive long distances in Hokkaido and observed the conditions under which they work. Most of their driving routes included steep passes, and the weather and the road conditions became worse in winter. Their tasks were not only the driving and waiting but also such manual labor as loading, etc. The mean driving distance of one route was 705 km and it ranged from 159 km to 1,210 km. The mean number of working hours was 27.8 h, and it ranged from 9.2 h to 46.9 h. Blood pressure was higher when driving or loading than when resting or on a day off. The mean systolic blood pressure was over 140 mmHg in 6 cases, and arrhythmia occurred frequently in 4 cases during driving or loading. In 2 cases, in which the driver met with accident, the blood pressure was remarkably high and arrhythmia occurred frequently. Most drivers worked for a very long time in poor conditions and environment. The results of our study suggested that such a heavy work load will affect the cardiovascular system.