Katsuo Nishiyama

Karoshi—Death from Overwork: Occupational Health Consequences of Japanese Production Management

There is considerable international interest in Japanese production management (JPM), known in the West as “lean production.” Advocates of this new form of management argue that it improves both economic productivity and health. In Japan, however, the relationship between JPM and sudden death due to cardiovascular and cerebrovascular disease has been an important topic of debate since the 1970s. Japanese have named these types of deaths karoshi, which means “death from overwork.” In North America and Western Europe a number of studies have demonstrated a significant relationship between high job strain (high production demands and low levels of control and social support) and cardiovascular disease. This article reviews the elements of JPM and examines their potential health consequences. The authors present an overview of karoshi, discuss its possible connections to specific ideological and organizational characteristics of JPM, and suggest the job strain mechanism as a possible pathway between karoshi and JPM. They conclude by discussing the need for comparative research that examines the health effects of work organization and management methods cross-culturally.

Preferred VDT workstation settings, body posture and physical impairments

In a field study an adjustable VDT workstation was given to each of the 68 operators for one week. The preferred settings, the body postures and subjective evaluations were assessed during normal working activities of the operators. The preferred ranges disclose the following figures: keyboard height (home row above floor) 71-87 cm, screen height (centre above floor) 92-116 cm, viewing angles (eye to screen centre) + 2 to -26 degrees, visual distance (eye to screen) 61-93 cm. There was practically no correlation between preferred settings and anthropometric data of body length or eye levels above floor. The study of body postures revealed that the great majority of operators tend to lean backwards with trunk inclinations between 97 degrees and 121 degrees (95% confidence interval). Some of the preferred settings strongly differ from those recommended in many brochures and standards. The physical complaints in the neck-shoulder and back area are diminished with the preferred settings.

Temporary threshold shift of vibratory sensation after clasping a vibrating handle

SummaryThe temporary threshold shift of vibratory sensation (TTSv) at 125 Hz after clasping a vibrating handle was investigated in relationship to four influencing factors: discrete frequency and acceleration of the vibration exposed to, the grip in clasping a handle and the time after exposure. Clasping the vibrating handle resulted in significantly larger TTSv than shown in clasping a non-vibrating handle. The TTSv after exposure to the 250 Hz vibration was significantly the largest in all frequencies at equal acceleration. The TTSv recovered exponentially as time elapsed after exposure. The TTSv also increased proportionally to the power of acceleration at each frequency and grip force. The larger grip force resulted in a significantly larger TTSv. A general form of regression equation of TTSv involving the four factors was established and its applicability was ascertained by a multiple regression analysis. The prediction equations obtained confirmed that a frequency around 200 Hz induced the largest TTSv among vibrations with equal acceleration and around 240 Hz among vibrations with equal velocity.

Measurement of Whole-Body Vibration in Taxi Drivers

Measurement of Whole‐Body Vibration in Taxi Drivers: Mitsuhiko Funakoshi, et al. Kyushu Institute for Social Medicine—In a previous epidemiological study we reported that the prevalence (45.8%) of low‐back pain (LBP) and the two‐year incidence (25.9%) of LBP in 284 male taxi drivers in Japan was comparable with rates reported for other occupational drivers in which LBP frequently occurs. LBP was significantly related with the level of uncomfortable road vibrations, and, importantly, increased with total mileage. The aim of this study was to measure whole‐body vibration (WBV) on the drivers seat pan of 12 taxis operating under actual working conditions. The results were evaluated according to the health guidelines in International Standard ISO 2631‐1:1997. Finally, the relation between total mileage and WBV was investigated. The majority of the frequency‐weighted r.m.s. accelerations of the taxis fell into the “potential health risks” zone, under ISO 2631‐1:1997. It was clear that the taxi drivers were exposed to serious WBV magnitudes. Therefore, occupational health and safety management should be carried out to help prevent adverse health effects in taxi drivers. In particular, reduction of WBV in taxis and shortening of driving time to reduce duration of WBV exposure should be considered. Moreover, because many taxi drivers work 18 h every other day, the shortening of working hours and taking of rest breaks while working should be considered. Frequency‐weighted r.m.s. accelerations of taxis had a tendency to decrease as total mileage increased. The relation between total mileage and WBV should be investigated by taking measurements on the floor and the back rest in addition to the seat pan.

Physiological Variations of Warm and Cool Sense with Shift of Environmental

In order to obtain control data on the temperature sense (warm and cool threshold values) of fingertips, the relationships between room temperature and either skin temperature, warm threshold or cool threshold of the middle fingertips were investigated in healthy subjects (6 males), using our thermo-esthesiometer. The skin temperature changes in a sigmoidal response with the variation of room temperature. A point of inflection for this response was observed at the room temperature of 15 degrees C, at which the greatest standard deviation of skin temperature occurred. The warm and cool thresholds, on the other hand, were also affected by variations of room temperature. Warm threshold and skin temperature or cool threshold and skin temperature bore a linear relation to each other, and the correlation coefficient was 0.854 in the former, and 0.925 in the latter, respectively. The disorder of temperature sensitivity (warm and cool thresholds) must always be considered together with the room temperature or skin temperature. On the other hand, the width of the neutral zone between warm and cool thresholds was affected by neither the changes of room temperature nor the changes of skin temperature. Hence, the width of the neutral zone was approximately constant, especially, at the room temperatures in the vicinity of 15 degrees C to 25 degrees C.

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.

Availability of temperature sense indices for diagnosis of vibration disease

SummaryThe correlation between stages of vibration disease and hypesthesia of temperature sense detected with our thermo-esthesiometer was analyzed. We measured the warm and cool thresholds among operators (644 males) in three occupational categories with vibration exposure from hand-held vibratory tools, such as grinder, drill, sander, impact-wrench, bush-cutter and chain-saw. Through the examination of the relationship between the temperature threshold and the stage of vibration disease, the following was revealed: The warm sense threshold elevated parallel with the aggravation of vibration disease, although the skin temperature had no change or reduction. The hypesthesia of the cool sense threshold appeared in serious cases of vibration disease. This abnormality of the cool sense indicated a more intensive disorder than that detected by the warm sense abnormality. The width of the neutral zone between the warm and cool thresholds of the intact subjects was 6.6° C±3.8 C°. This neutral zone was enlarged with the aggravation of the vibration disease. Data also showed that the measurements of temperature sense threshold should be carried out under standardized room temperature.

Temporary threshold shift of temperature sensation caused by vibration exposure

SummaryThe temporary threshold shift of temperature sensation due to vibration exposure was studied to clarify the significance of frequency and acceleration on it. The discrete frequencies of the vibrations tested were 32, 63, 125, 250 and 500 Hz, and the accelerations were at the level of 2, 4, 8 and 16 g. The threshold shift of warm sensation (TTSw) was markedly, but that of cool sensation was small and not significantly different from the control value. TTSw increased with a rise in the level of acceleration and was largest at 125 Hz among the frequencies examined. The most effective frequency among the vibrations tested for warm sensation was inferred to be lower than that for vibratory sensation. After exposure, TTSw or the increment of the neutral zone decayed exponentially but bounced slightly in the later period. These patterns of TTSw are similar to those of the vibration-induced TTS of vibratory sensation.

Application of a new, self-recording, vibratory sensation meter to measure temporary threshold shift of vibratory sensation caused by local vibration exposure

A new, self-recording, vibratory sensation meter measures temporary threshold shifts of vibratory sensation (TTSv) on a finger tip. After exposure to hand-transmitted vibration with exposure frequencies 63 Hz, 200 Hz and 500 Hz, and levels of acceleration 1 g, 2 g, 4 g and 8 g, fingertip measurements were obtained. Temporary threshold shift immediately after the vibratory exposure (TTSVv,0) was estimated for each exposure from the regression analysis by approximation of an exponential function. Time constant (tc) was also estimated at the same time by the analysis. The coefficients of determination were large. Thus, the fit of the exponential function is very good for each exposure. The tc corresponds to the recovering velocity of the temporary shift and implies the half-life period of TTSv. These parameters enable us to examine more generally the relationships of TTSv to the characteristics of exposure vibration, subject and other conditions. On this basis, the estimated TTSv,0 and tc were used to examine the dependency of TTSv on the characteristics of the exposure vibration and the subject. The most effective frequency under the level of 4 g is thought to be between 200 Hz and 500 Hz. TTSv,0 of each subject proportionally increased with power of acceleration. The coefficient of determination on regression analysis was large. This result enables us to estimate TTSv,0 at an arbitrary level of acceleration by use of a regression equation derived from experimental data.

Lean Production and Worker Health: A Discussion:

LANDSBERGIS: New systems of work organization have been introduced by employers throughout the industrialized world in order to improve productivity, product quality, and profitability. Such efforts have taken a variety of forms and names, including lean production, total quality management, re-engineering, and modular manufacturing, and have often been extolled as reforms of Taylorism and the traditional assembly-line approach to job design. While the new systems can introduce profound changes in the way work is designed, few studies have examined the impact of such systems on work injuries (especially work-related musculoskeletal disorders) or on job characteristics related to job strain (that is, jobs defined by high demands, low control, and low support), which have been linked to the development of hypertension and cardiovascular disease. In addition, lean production and related new work systems may impact on worker skill development, co-worker support and solidarity, and union strength, and may, in turn, be modified by union efforts. Therefore, we asked a number of researchers and educators in the field to discuss the impact of lean production on worker health and safety and related job characteristics. Paul Adler, University of Southern California, has studied the New United Motors Manufacturing, Inc. (NUMMI) auto assembly plant, a General Motors (GM)–Toyota joint venture in Fremont, California, and compared it to Scandinavian auto plants on productivity and quality, as well as ergonomics. Paul Landsbergis, Cornell University Medical College, has