Decrease in Work Ability Index and sickness absence during the following year: a two-year follow-up study.

PURPOSE: Using a 2-year follow-up design, we examined whether changes in work ability during 1 year predicted sickness absence in the following year. METHODS: Workers (N = 1408) from the Japanese information technology sector each completed the Work Ability Index (WAI), the Brief Job Stress Questionnaire (BJSQ), and the General Health Questionnaire (GHQ) in 2011 and 2012. Absence data during 2013 was obtained from employees' computerized attendance records. We used psychological distress as evaluated by the GHQ; job stress and job support calculated using the BJSQ; and job title, sex, and age as potential confounding variables. RESULTS: Thirty-five employees had at least one sickness absence lasting more than seven consecutive days in 2013. Forty-nine percent of sickness absences were due to mental illness, and the others were due to orthopedic disease (20%), cancer (9%), and other illnesses (23%). Decrease in WAI scores from 2011 to 2012 predicted sickness absence in 2013 (Odds ratio (OR) 1.19, 95% confidence interval (CI) 1.12-1.27). This association remained unaltered after adjusting for sex, age, job title, WAI score from the year before, job stress, job support, and GHQ score (OR 1.15, 95% CI 1.06-1.25). We analyzed this association separately by reason for absence: mental or other illness. WAI score decreases predicted sickness absence for both reasons (OR for mental illness 1.24, 95% CI 1.14-1.36; OR for other illnesses 1.14, 95% CI 1.04-1.24). CONCLUSIONS: Decrease in work ability during the year predicts sickness absence in the following year while predictive power was weak.

Work improvement factors for the amelioration of work ability, with a focus on individual capacity to deal with stress in an IT company.

The aim of this study was to explore factors that ameliorate work ability by focusing on workers' capacity to deal with stress.The subjects were 1,330 workers from the Japanese information technology (IT) sector. Each subject completed questionnaires in 2011 and 2012 that consisted of the work ability index (WAI), the three-item sense of coherence (SOC), and the Mental Health Improvement and Reinforcement Research of Recognition (MIRROR). The results of the WAI were also obtained in 2013. The median SOC score in 2011 was used to divide the subjects into two groups, the Low SOC group and the High SOC group, then we verified the factors that contributed to improved work ability in both of these groups over a two-year period. Results indicate that an improvement in work ability in the Low SOC group could be predicted by giving workers opportunities for education or training, by making efforts to reduce the stress of commuting, by clarifying their assignments, and by establishing support systems when troubles occur. For the High SOC group, such improvements could be predicted by giving workers job control, by giving education or training for the promotion of their abilities, and by establishing a system for assuming responsibility. In conclusion, improvements in the work environment can increase the work ability of Japanese IT workers in conformity with their capacity to deal with stress.

Effects of bench step exercise intervention on work ability in terms of cardiovascular risk factors and oxidative stress: a randomized controlled study.

Work ability is partly determined by physical and mental fitness. Bench step exercise can be practiced anywhere at any time. The aim of this study was to determine the effects of a bench step exercise on work ability by examining cardiovascular risk factors and oxidative stress. Thirteen volunteers working in a warehousing industry comprised the bench step exercise group (n=7) and the control group (n=6). The participants in the step exercise group were encouraged to practice the step exercise at home for 16 weeks. The step exercise improved glucose metabolism and antioxidative capacity and increased work ability by reducing absences from work and improving the prognosis of work ability. The improvement in work ability was related to a reduction in oxidative stress. These results suggest that a bench step exercise may improve work ability by reducing cardiovascular risk factors and oxidative stress.

The relationship between work ability and oxidative stress in Japanese workers.

Work ability is based on the balance between personal resources and work demand. This study focused on the personal resources component of work ability. The aims of this study were to elucidate the association between work ability and cardiovascular (CV) risk factors, particularly oxidative stress, and to estimate the effect of a community-implemented lifestyle modification programme on work ability and CV risk factors. Urinary 8-iso-prostaglandin F2α (PGF2α), a biomarker of oxidative stress, was negatively correlated with psychological resources, as measured by the Work Ability Index (WAI). Overall WAI score was unchanged following the programme, while CV risk factors and antioxidative activity improved. A reduction in PGF2α levels was correlated with an improvement in subjective work ability relative to job demands, as assessed by a WAI item. Taken together, the results suggest that lifestyle modification programmes enhance the personal resources component of work ability and are associated with a reduction in oxidative stress.

Validity and reliability of Japanese version of the MAPO index for assessing manual patient handling in nursing homes.

OBJECTIVES: Low back pain (LBP) among caregivers in Japanese nursing homes has long been considered an occupational health issue. This study aimed to verify the reliability and validity of our developed Japanese version of the Movement and Assistance for Hospitalized Patients (J-MAPO) index, a risk assessment tool for LBP, in nursing homes. METHODS: Two inspectors assessed 15 nursing homes using J-MAPO, and deduced 3 LBP risk levels as follows: low, moderate, and high risk. Caregivers in nursing homes responded to a self-administered questionnaire on LBP over the past 12 months. Data from 296 caregivers with no missing data were used. We further used logistic regression models to analyze the association between LBP as a dependent variable, and J-MAPO risk level as an independent variable. We used Cohen kappa coefficient to assess interrater reliability to further assess the agreement between the 2 inspectors. RESULTS: The multivariate logistic regression analysis showed that the adjusted odds ratio and 95% CIs for LBP increased progressively with J-MAPO risk level (Low-risk: 1.00; Moderate-risk: 1.70 [0.74-3.91]; High-risk: 2.67 [1.28-5.56]). Furthermore, the J-MAPO risk levels assessed by the 2 inspectors were in perfect agreement (κ = 1) observed for interrater reliability using Cohen kappa coefficient. CONCLUSIONS: There was high interrater reliability, and J-MAPO risk levels were associated with LBP. Therefore, our results suggest that the J-MAPO is a useful risk assessment tool for LBP in Japanese nursing homes.

The effects of static trunk flexion on oxygenation and electromyographic activity of erector spinae muscles.

In the workplace, localized muscle fatigue can be a limiting factor for prolonged static work. It is important to study the etiology of fatigue in the muscle to prevent discomfort and potential muscle injury. The purpose of this study was to investigate the effect of sustained trunk flexion and loading on the erector spinae muscles (ESM) fatigue using electromyography (EMG) and muscle oxygenation (Mox) changes. Twelve healthy male volunteers, aged between 19 and 28 years (mean age 23 +/- 2.6), participated in this study. The subjects held a load (5, 10 and 15 kg) and no load in their hands whilst sustaining trunk flexion at 60 degrees and also in an upright standing posture for 30 seconds. Five minutes rest was given between the conditions, and each condition was randomly repeated three times. Surface EMG and near-infrared spectroscopy were recorded. Root mean square and median frequency (MF) of EMG, and Mox were calculated. The results showed a greater decrease in Mox with an increase in loads over time (P = 0.015). Using unloaded trunk flexion as a control to ascertain load effect resulted in a significant difference in Mox in the unloaded condition and in the 15 kg condition (P = 0.027). EMG results showed a significant decrease in the MF over time in trunk flexion while holding a load (P < 0.001). These results show objectively that trunk flexion while holding loads causes ESM fatigue.

Fatigue sensation, electromyographical and hemodynamic changes of low back muscles during repeated static contraction.

The effects of work strategy and a rest condition on the physiological changes of the erector spinae muscle were studied. Eleven volunteers repeated fatiguing static contractions of holding an industrial box in 30° trunk flexion for a repetition of 12 times interrupted by rests for which the duration was equal to the duration of each preceding contraction. Each contraction was stopped at two fatigue sensation levels; moderate or strong, which corresponded to Borg's CR-10 3 and 5, as the work strategy conditions. The repeated contractions were performed for a total of eight conditions combined with the two rest conditions, with and without stretch exercise, and two contraction levels of 10 and 40% maximum pulling force in flexed posture (MVC) on separate days. Near-infrared spectroscopy and surface electromyography (EMG) were recorded. Amplitude and median frequency (MF) of EMG, oxy-hemoglobin, and deoxy-hemoglobin were calculated. MF related to fatigue sensation most closely. Oxy-hemoglobin decreased during each contraction. It, however, increased with repetition especially at 10% MVC and the increase was interpreted as adaptation to the work. The effect of the work strategy and the rest conditions was weak. MF decreased more in a strong work strategy condition than in a moderate one.

Lifestyle and subjective musculoskeletal symptoms in young male Japanese workers: A 16-year retrospective cohort study.

This longitudinal study was conducted from 2002 to 2018 and aimed to investigate predictive lifestyle factors for the occurrence of subjective musculoskeletal symptoms. The participants came from several employers in Japan. Setting 2002 as the baseline, we performed logistic regression analyses using lifestyle questionnaire items as explanatory variables and Stiff neck/shoulders (SN/S) and Lower back pain (LBP) as objective variables (n = 16,748). Workers who responded positively to good lifestyle items with an odds ratio < 1.0 and those who did not were classified in the Good (GL) and Poor lifestyle groups (PL), respectively. The survival period between the groups was compared using the log-rank test and Cox hazard regression analysis with propensity score matching (n = 3,593). Based on the Cox hazard regression analysis results, the risk of SN/S was about 2.54 (95% confidence interval [CI]: 1.80-3.59) times higher for PL than for GL (p < 0.001). Similarly, after propensity score matching, the risk was about 2.33 (95% CI: 1.07-5.10) times higher for PL than for GL (p < 0.05). Further, LBP risk was about 2.45 (95% CI: 1.67-3.58) times higher for PL than for GL (p < 0.001). Similarly, after propensity score matching, the risk was about 3.50 (95% CI: 1.60-7.68) times higher for PL than for GL (p < 0.01). This study highlighted that workers with four good lifestyle factors (life satisfaction, hours of sleep, exercise habits, and physical fitness) presented reduced risk of subjective musculoskeletal symptom occurrence. To prevent musculoskeletal symptoms, physicians and occupational health staff should advise on workers' individual lifestyle.

[A case study of tailor-made exercise for preventing decrease in physical function: Analyzing the effect of tailor-made exercise from a motion study, motor function test, and questionnaire].

OBJECTIVE: This study aimed to verify the effect of tailor-made exercise depending on the characteristics of a certain food manufacturing industry on the physical function and subjective symptoms of employees. METHODS: For the development of tailor-made exercise, work analysis was carried out at each factory to comprehend the physical burden due to work load. The motor function test and questionnaire survey for subjective symptoms were conducted before and after exercise during 3 months. The motor function tests included the 30-s chair-stand test and two-step test. RESULTS: There were significant improvements in the 30-s chair-stand test after tailor-made exercise intervention for men and women (men: 20.9±4.8 vs 27.9±5.1 counts/30 s, p < 0.01; women: 19.4±3.1 vs 23.7±2.7 counts/30 s, p < 0.01) but not in the two-step test. In addition, as a result of comparing the questionnaire survey for subjective symptoms before and after intervention, there was a significant difference (p < 0.05) in "stumbling and staggering within 1 month," "feeling of fatigue in the back," "feeling of fatigue in the right foot/ankle," and "feeling of fatigue in the left foot/ankle." CONCLUSIONS: It is thought that the leg muscle strength increased due to tailor-made exercise, and the stumbling and staggering improved. In addition, feeling of fatigue in the back and in the right and left foot/ankle was improved. It was suggested that tailor-made exercise intervention can significantly affect the physical function of employees.

Effect of the balance between operators' processing abilities and required operating speed on operators' task performance and psycho-physiological state during simple repetitive work under time constraints.

The aim of this study is to reveal the effect of the balance between operators' processing abilities and the time constraints imposed upon them in simple repetitive work. In the present study, three experimental conditions for the same tasks which are original pattern recognition ones, but with different ways of setting time limits, were prepared: one time limit was adjusted to each subjects' ability, the second was a uniform and relatively strict time limit, and the third was a uniform and relatively lax time limit. For these three experimental conditions, comparisons were made of task performance indices, subjective indices (NASA-TLX: NASA-Task Load Index, SACL: Stress-Arousal Checklist), and physiological indices (frontal midline theta activity at Fz and the fast a activity at Pz in EEG, and heart rate in ECG). The results showed that individual differences were extremely large in terms of time pressure (TP) effects on task performance and operators' psycho-physiological state if a uniform and strict time limit was imposed on operators with different abilities. Meanwhile, the negative effects of TP on operators were small if they were given a uniform time limit but with enough allowance time. In addition, the results from the frontal midline theta activity in EEG suggest that the patterns in changes of concentration of attention on tasks were different according to the way that the time constraints were set.

Occupational low back pain among workers in some small-sized factories in Ardabil, Iran.

The main purpose of this study was to assess some of the individual and occupational risk factors contributing to induction or intensification of LBP among the employees suffering from this problem in four small size factories in Ardabil, Iran. This study was a cross-sectional study that was conducted among the personnel of four industrial companies. Interview, questionnaire survey, medical examination (Lasegue test), radiographic evaluation, and ergonomic survey (using the NIOSH checklist) were the methods to collect data. The result of the study was divided into two parts: individual factors and work-related factors. The highest frequency of low back pain was observed in the age of 30-34 years old, medium height and heavy weight with 34.4, 84.4, and 33.0 percent, respectively. With regard to work-related factors, load lifting with 44.7 and body posture with 18.4 percent contributed to low back pain as the most important occupational causes among the patients. Observing recommended regulations and limitations of load lifting, modifying and optimizing ergonomic conditions in the workplace, selecting workers with suitable body strength on the basis of a pre-employment examination and implementing a continuous educational program for employees were the most important methods recommended to prevent low back pain.

Prevalence of respiratory symptoms among workers in industries of south Tehran, Iran.

OBJECTIVE: The aim of the present study was to determine the prevalence of respiratory symptoms from occupational lung hazards among workers in industries of south Tehran, IRAN. METHODOLOGY: This was a cross-sectional study in which by multistage random sampling items on demographic characteristics, cigarette smoking, occupational history and respiratory symptoms were collected of workers. RESULTS: The mean age of the workers was 38.5 (SD = 10.2) yr: age ranged from 19 to 70 yr. Of 880 workers under study, 252 (28.7%) were smoking. Also, it has been observed that workers exposed in the workplace with occupational chemical exposures such as dust, gas and fume pollutants. The prevalence of respiratory symptoms was cough (20.7%), phlegm (41.6%), dyspnea (41.7%), feel tightness (27.4%) and nose irritation (23.5%). CONCLUSIONS: Occupational exposures among workers in industries of south Tehran may cause respiratory symptoms and respiratory disorders, engineering controls and industrial hygiene is recommended.

Sense of coherence modifies the effect of overtime work on mental health.

OBJECTIVES: In the occupational health field, it is important to know how workload influences mental health. Overtime work and job strain appear to affect the mental health status of workers. Sense of coherence (SOC) may mediate the relationship between work stress and mental health. Since SOC represents a personal ability to manage psychological stressors, we hypothesized that a strong SOC would modify the adverse effect of an objective measure of overtime work on mental health. METHODS: A total of 1,558 Japanese workers employed in an information technology company were asked to complete a 3-item SOC Questionnaire and 28-item General Health Questionnaire (GHQ) to assess mental health status. Workload was assessed by the actual amount of overtime work hours recorded by the company. RESULTS: Multiple regression analysis revealed a main effect of overtime work (ß=0.08, p=0.0003) and SOC scores (ß=0.41, p <0.0001) on GHQ scores. There was a tendency toward interaction between overtime work and SOC scores (ß=0.05, p=0.051). Simple slope analysis supported this association (-1 SD below the mean, simple slope=0.04, SE=0.01, p < 0.0001; +1 SD above the mean, simple slope=0.01, SE=0.01, p=0.188). CONCLUSIONS: These results suggest that SOC buffers the mental health impacts of workload as measured by an objective index of overtime work, and should be considered when assessing the effects of workload on mental health.

[Intermodal timing cues for audio-visual speech recognition].

The purpose of this study was to investigate the limitations of lip-reading advantages for Japanese young adults by desynchronizing visual and auditory information in speech. In the experiment, audio-visual speech stimuli were presented under the six test conditions: audio-alone, and audio-visually with either 0, 60, 120, 240 or 480 ms of audio delay. The stimuli were the video recordings of a face of a female Japanese speaking long and short Japanese sentences. The intelligibility of the audio-visual stimuli was measured as a function of audio delays in sixteen untrained young subjects. Speech intelligibility under the audio-delay condition of less than 120 ms was significantly better than that under the audio-alone condition. On the other hand, the delay of 120 ms corresponded to the mean mora duration measured for the audio stimuli. The results implied that audio delays of up to 120 ms would not disrupt lip-reading advantage, because visual and auditory information in speech seemed to be integrated on a syllabic time scale. Potential applications of this research include noisy workplace in which a worker must extract relevant speech from all the other competing noises.

Effects of screen size and task difficulty on vigilance performance of older adults.

This paper describes an experiment to elucidate the effects of aging on vigilance performance with VDTs. In addition, the experiment was undertaken to evaluate whether the aging effects are affected by the degree of task difficulty and by the screen size of the VDTs. Forty healthy male volunteers were studied in two age groups of 20 participants. In the experiment, the participants were required to perform vigilance tasks, which were presented either on a conventional 17-inch display or a large-sized 110-inch display. The 60-minute task period was divided into three 20-minute phases assigning the tasks with two scenarios of different degrees of difficulty. Performance was measured using reaction time for detection and number of detection errors. The results pointed out three effects: (1) the performance of the vigilance tasks deteriorated more markedly among the older adults than among the younger adults; (2) the between-screen differences on the vigilance performance were significant for the older adults, but not for the younger adults; (3) the effect of screen size was amplified by increasing the degree of task difficulty. These data indicate that screen size and task difficulty have an effect on vigilance performance with VDTs of older adult.

[How many ergonomics interventions do we have in the field of occupational stress?].

This paper describes handling stress in the workplace from the viewpoint of work conditions and ergonomics. The term expressed in Japanese as "sagyokanri" corresponds to the term "work conditions and ergonomics" in English, which is used internationally in the field. Therefore, "sagyokanri" means considering how to handle work and stress by using ergonomics. The Japanese Journal of Ergonomics is quoted in this discussion of the definition of stress and the lack of countermeasures taken with respect to work conditions and ergonomics as they relate to stress. Finally, it touches on the SACL (Stress Arousal Checklist), one method of evaluating stress which is not very familiar to those in the occupational health field in Japan.

[Comparison of Work Ability Index and cognitive function tests].

The purpose of this study was to evaluate the effect of aging with regard to scores for certain cognitive function tests and WAI (Work Ability Index), and to examine the relationship between cognitive function test scores and work ability as measured by WAI. The subjects were 139 male employees of a factory producing steel plate, and their average age was 48.1 yr (SD 16.4). The WAI and cognitive function tests were conducted and valid scores were obtained from 134 subjects as to WAI, and from 88 subjects as to cognitive function tests. The subjects were divided into two groups: young workers (under 45 yr) and middle-aged to elderly workers (45 yr and over). The WAI scores of the two groups were compared, but no significant differences were observed. Nevertheless, for two WAI items, WAI-2 and WAI-7, the scores of the middle-aged to elderly worker group were significantly higher than those of the young worker group. In contrast, the scores for WAI-3 of the middle-aged to elderly group were significantly lower than those of the young worker group. The cognitive function test scores for the two groups were also compared. The scores for Working Memory test, Tracking test, and Sentence-to-sentence Comparison test of the middle-aged to elderly worker group were significantly lower than those of the younger group. Moreover, for the middle-aged to elderly worker group, the average WAI-3 scores for those with good cognitive function test results and those with poor cognitive function test results were compared, but there were no significant differences. This result shows that deterioration of physical function caused by aging is not related to deterioration of cognitive function caused by aging in the subjects of this study. The reason for this may be that the subjects are blue-collar workers, and thus cognitive functions are less important for their work.

[Association of working postures and some lifestyles with low back pain in a manufactory].

The aim of this study was to determine the relationship between work and low back pain (LBP) by examining both working postures and the workers' everyday lifestyle. Subjects were 118 male workers in a small-to-medium-sized factory having three kinds of workplaces: the slit line, the packing line, and the crane unit. Working posture analysis with OWAS and interviews were carried out. The result of posture analysis showed that the standing posture with both legs straight and back bent appeared most frequently in all three workplaces. Meanwhile, the prevalence of LBP was almost equal among these groups, with 70% of workers having experienced LBP in each group. But the main cause of LBP differed among the three groups. On the slit line, the result of regression analysis and interview suggested that exercises in the past affected the prevalence of LBP, and that aging and work made LBP worse. On the packing line, many workers were transferred to other positions after a few years, and thus might affect the prevalence of LBP in other workplaces. For the crane unit, it appeared that work in previous positions might affect the occurrence of LBP. Moreover, it seemed that activities in the workplace, rather than lifestyles, contribute to the occurrence of LBP in this factory.

Visual recognition memory test performance was improved in older adults by extending encoding time and repeating test trials.

OBJECTIVES: The aim of this study was to investigate whether the combination of extension of the encoding time and repetition of a test trial would improve the visual recognition memory performance in older adults. METHODS: We evaluated visual memory performance in young and older adults on a Yes-No recognition memory test under four different conditions. The conditions consisted of combinations of encoding times of two and four seconds (E2 and E4) and first and second retrieval practice test trials (T1 and T2): E2T1, E2T2, E4T1 and E4T2. Performance was evaluated by measuring hit rates, false alarm rates, discrimination ability and response bias. RESULTS: Older adults showed better improvement of hit rate and discrimination ability under the E4T2 conditions whereas young adults showed better memory performance under the E2T2 conditions. CONCLUSIONS: A longer encoding time and repetition of the test was effective in improving the visual memory performance in terms of the hit rates and discrimination ability of older adults. The results suggest that this strategy should be useful in providing a suitable work environment for older workers.

Kaizen: ergonomics approach to occupational health and safety.

Kaizen (work improvement) is the forte of Japanese industry. Kaizen activities were born in the early 20th century under the name efficiency research. These activities were the beginning of industrial engineering (IE). Later on people began to rethink the single-minded devotion to improving productivity. Then the job re-design concept was developed. The main target of kaizen in the area of occupational health and safety in Japanese manufacturing is the improvement of inadequate working posture followed by the improvement of work for transporting and lifting heavy objects. Unfortunately, the kaizen activities undertaken by most Japanese companies are still focused on improving productivity and quality. The know-how for promoting kaizen activities that integrate the three aspects of IE, occupational health, and ergonomics is not being accumulated, however. In particular, the IE techniques should be incorporated into kaizen activities aimed at occupational safety and health, and the quantitative assessment of workload is required. In addition, it is important for on-the-job kaizen training in the ERGOMA Approach for production supervisors, who are the main advocates of IE kaizen.