Karoshi-Death from overwork: Occupational health consequences
of the Japanese production management
(Sixth Draft for International Journal of Health Services)
(February 4, 1997)

Katsuo Nishiyama and Jeffrey V. Johnson
Department of Preventive Medicine, Shiga University of Medical Science, Japan
Department of Health and Policy Management
School of Hygiene and Public Health,
Johns Hopkins University, USA

Reprint requests to:
Dr. Katsuo Nishiyama, Department of Preventive Medicine
Shiga University of Medical Science, Tsukinowa-cho, Seta, Otsu, 520-21 Japan
Phone +81-775-48-2187

Biographical Sketches

KATSUO NISHIYAMA is a Professor in the Department of Preventive Medicine at the Shiga University of Medical Science in Otsu, Japan. He holds a Bachelor of Engineering in polymer chemistry from Kyoto University (1965), a D.Phil. in ergonomics from Osaka University (1984) and an MPH in occupational health from The Johns Hopkins University (1994). He was a guest researcher at the Institute of Work Physiology and Hygiene of the Swiss Federal Institute of Technology (ETH), Zürich, during 1981-1982. Dr. Nishiyama was formerly at the Department of Hygiene of the Kansai Medical University. His research has focused on occupational health related to the modern rationalization of the Japanese industry.

JEFFREY V. JOHNSON is an Associate Professor of Social and Behavioral Sciences in the Department of Health Policy and Management at The Johns Hopkins School of Hygiene and Public Health. He also holds appointments as an Associate Professor in the Departments of Environmental Health Sciences, of Medicine, and of Sociology. His research integrates sociological and epidemiological perspectives on the impact of work organization on chronic disease. He has worked at the Division of Organizational and Work Psychology at the University of Stockholm, the Department of Psychosocial Environmental Medicine at the Karolinska Institute in Stockholm and at the Catalan School of Public Health in Barcelona, Spain. He received his Ph.D. from The Johns Hopkins School of Public Health in 1986. Before his academic career, he worked as a journeyman newspaper pressman.


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 1970's. Japanese have named these types of deaths karoshi, which means ‘death from over work’. 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. After describing JPM and its ideological and organizational characteristics, we address its relation to job strain and examine how karoshi can be understood as a response to JPM. We conclude by discussing the need for comparative research that examines the health effects of work organization and management methods cross-culturally.


The first case of karoshi was reported in 1969 with the death from a stroke of a 29- year old, married male worker in the shipping department of Japan's largest newspaper company [1]. Karoshi can be translated quite literally as "death from overwork." The major medical causes of karoshi-deaths are heart attack and stroke, including subarachnoidal hemorrhage (18.4%), cerebral hemorrhage (17.2%), cerebral thrombosis or infarction (6.8%), myocardial infarction (9.8%), heart failure (18.7%), and other causes (29.1%) [2]. The Ministry of Labor began to publish the statistics on karoshi in 1987, as public concern increased [3]:

For example, a big life insurance company investigated 500 male white-collar workers in top-ranking corporations in Tokyo. The report shows that 46 percent of respondents were anxious about their own risk of karoshi. A quarter of them experienced complaints from their families related to anxiety about karoshi. Around 5 to 20 percent of the workers themselves were afraid of the high risk of karoshi. This fear increased with age. The report also shows that family members are much more afraid than the workers themselves. Nowadays, there are almost no workers who do not know the word [karoshi]. Many Japanese workers and their families are anxious about karoshi.

There are no epidemiologically sound estimates of the prevalence and incidence of karoshi. Until recently, there were 20 to 60 deaths each year from overwork for which the Ministry of Labor awarded compensation. However, critics state that the number of people the Ministry compensates for such deaths is much less than their actual occurrence [4]. The overall number of deaths related to cerebrovascular or cardiovascular disease in the 20 to 59 age group is around 35,000 per year according to vital statistics data. Kawato estimates that one-third of these are work-related, or more than 10,000 each year [4]. In 1994, the Japanese government's Economic Planning Agency in the Institute of Economics estimated the number of Karoshi deaths at around 1,000 or 5 percent of all deaths from cerebrovascular and cardiovascular disease in the 25 to 59 age group [5].


Early History

The first case of karoshi was initially called occupational sudden death. Shift work and an increased work load, together with excessive overwork in spite of ill health just before the stroke, were finally recognized as the occupational causes of death by the Workers Compensation Bureau in the Ministry of Labor. It took five years for the family to receive compensation. Since then other cases of Karoshi in the newspaper industry have been comparatively well documented by the labor movement, which identified 18 such cases in the 1970s [2].

When Hosokawa indicated that Karoshi was caused by occupational exposures in a cross-sectional questionnaire survey of workers in the newspaper industry in 1971 [6], there was little, if any, research studying the effects of shift work and hours of work on cardiovascular or cerebrovascular disease. During the 1970s there had been no reports of karoshi type deaths in the Western industrialized countries. At that time the research was focused on Type A behavior as a risk factor for coronary heart disease. The concept of Type A was introduced to Japan through the international literature [7]. Most Japanese researchers and physicians did not consider Type A as being directly applicable to karoshi because comparatively few of the victims in the 1970s were executives and managers. Most of the karoshi cases of this period consisted of shift workers, drivers, newspaper and television workers, construction workers, and salesmen. These were not the same occupational groups that had been identified as being at risk for Type A behavior in the West.

It was the pressure from karoshi victims' wives and colleagues motivated physicians to investigate the work-relatedness of these deaths. The estimated number of compensated deaths in the 1970s was approximately 100. On the basis of case studies, major preventive measures were proposed that the public thought could prevent karoshi [8]. Some physicians urged the use of an epidemiological approach. Epidemiology in occupational health, however, was in its infancy and major studies were not initiated. (Not until 1992 was the Association of Epidemiology established in Japan and it has taken many years for epidemiology to be recognized as a science in the medical community.)

The Japanese Association of Industrial Hygiene (JAIH) established the three-year Shift Work Committee in the late 1970s to study the relationship between shift work and workers' health and to recommend occupational health measures. The committee did a nationwide cross-sectional study using questionnaires. Although the report did not refer to karoshi, it showed that workers engaged in two-shift systems had more health problems [9].

In 1982, the first book entitled "Karoshi" was published by three physicians [6]. This was the origin of the term karoshi. The major approach to research on karoshi was an accumulation of cases and an emphasis on assembling proof of causality on an individual basis. This case study analysis indicated that karoshi deaths were associated with long working hours, shift work, and irregular work schedules [10,11,12] . Most karoshi victims had been working long hours equivalent to more than 3,000 hours per year, just before death.

The National Defense Council for Victims of Karoshi was established in 1988 by the leading lawyers for karoshi. A karoshi hot line was opened on a certain date every year in every prefectural city. In 1990, "Karoshi--When the Corporate Warrior Dies" was published in English [2], and the term karoshi entered the English language; some foreign newspapers and television networks also reported on karoshi deaths [13].

In 1991 advertisements about karoshi appeared in foreign newspapers. Missions were sent to foreign countries; counseling offices opened for overseas Japanese workers in New York and Brussels, and the matter was filed with the Subcommittee of Human Rights of the United Nations. The Ministry of Labor established a Committee of Work-Related Vascular Diseases in response to increasing public concern.

Trade unions, physicians and academics at the local level have acted, from time to time, as advocates, helping the families of victims and demanding prevention. But it has taken almost two decades to rouse public concern for karoshi. In 1992, the JAIH (the only national level academic organization for occupational health professionals), established the two-year Committee on Work-Related Vascular Diseases in response to a proposal from its members. The Committee's major activity is to review the literature, the karoshi cases, and the legal precedents. The Committee itself has not promoted its own biomedical or epidemiological investigation. There is still no epidemiological investigation of karoshi covering the national population .

Workers' Compensation for Karoshi

The government has been reluctant not only to conduct an investigation but also to compensate karoshi through the Workers' Compensation system. The compensation policy is based on accidental death and thereby tends to obscure the health consequences of long term exposures that are a normal part of JPM. The government did not release the statistics on claims and compensated cases until 1987. The Ministry of Labor asks workers compensation claimants to prove that the karoshi victim was engaged in extremely burdensome work or was injured in an accident -- that the event greatly exceeded the normal work load just before or at least on the same day as the heart attack or stroke. The Ministry of Labor's Confidential Manual states that overwork could be the cause of death only if the worker was engaged continuously for 24 hours just before death or worked at least 16 hours a day for seven consecutive days before death [14]. Such working conditions would fit into the rubric of being "accidental" in those corporations where it occurs. The manual states that the worker must have worked more than twice the regular hours during the week prior to collapse, or three times the regular hours the previous day. Another states that just one day off during the week prior to collapse disqualifies the karoshi death from compensation, even if the worker had worked twice the regular hours on the remaining six days. Otherwise, claimants have been obliged to prove biomedically the occupational causality of the death. The Ministry of Labor revised the criteria for compensation for cerebrovascular disease and ischemic cardiovascular disease in 1987. The essence of the criteria, however, did not change [11].

The essential problems with the current criteria are illustrated by the following example: In 1994, the Inspectorate of the Office of Labor Standards refused to award worker's compensation for a 42-year old truck driver who died of acute myocardial infarction. His annual working hours totaled 5,700 hours. He had been employed as a truck driver for 11 years. The office recognized this as normal daily work because the driver had worked approximately 6,000 hours for the past six or seven years. Other drivers also work similar hours. The government has tended to overlooking these long hours of work.

Responding to public concern, the Ministry began to release the statistics on karoshi cases in 1987. The number of compensation claims to the Ministry of Labor is thought to be much less than the actual occurrences. The small rate of compensation, the very long time taken to get a decision on whether or not the death will be compensated, and the very stringent application of the criteria of the Ministry of Labor often discourage the victims' families from filing their claims with the compensation apparatus.

Examples of Corporate Prevention Measures

The state of the art in karoshi prevention in Japanese corporations is very superficial as shown by the following examples [12]:

The employee whose overtime hours for a 3-month period exceed the standard determined by the corporation receives a health examination by the industrial physician; annual physical strength tests are conducted. Employees of an office machine manufacturer, for example, are informed of any change since their last test and advised of their strength as compared with national statistics;

(1) Employees of a trading company out on sick-leave are telephoned and not forced to commute;

(2) Early morning sales conferences that could not be finished the previous day are dropped at an office machine sales company;

(3) Smoking regulations are lowered in a motor manufacturing company from 2 hours a day to 10 minutes at 10:00 a.m. and 3:00 p.m.; and

(4) Employees of a machine manufacturing firm are assisted in finding a funeral home and making funeral arrangements.


Gourika-Byou (diseases of rationalization)

Research orientations change over time. The RMR (Relative Metabolic Rate) oriented era continued for two decades until just after Word War II. RMR was studied vigorously for many kinds of tasks in order to improve the physiological aspects of work pace and scheduling. The next historical period focused on fatigue. Work related fatigue was studied from the physiological and psychological aspect even as JPM was developed and spread. More recently, occupational health researchers -- particularly in Europe -- have performed many investigations of the relationship between work environment conditions and physiological reactions in order to determine standards for working conditions, such as maximum allowable work periods and the degree of work output in order to prevent stress and fatigue in mechanized jobs.

It has not been clear how karoshi fits into these historical paradigms in occupational health. One problem is that there continues to be considerable confusion about the concept of karoshi and indeed some researchers have considered the term itself problematic. Some call it, "not of pure medicine" but a socially constructed disease entity that is not ‘real.’ Japanese scientists have not agreed on a single definition, the kinds of death involved or whether only death itself should be included. As mentioned earlier, karoshi involves not just death from cardiovascular disease, but can also include other acute deaths, i.e., those related to delayed medical treatment because of lack of free time to see a doctor, and suicides attributed to overwork. For example, some karoshi victims have died due to diabetic coma, rupture of the esophageal vein related to liver malfunction, peptic ulcer, bronchial asthma, and so on. Case fatality rates also vary according to factors other than overwork. If a victim fortunately survives, the case may not be treated in the context of occupational causality. Indeed, deaths may only be the tip of the iceberg -- the most visible indicator of the health effects of overwork in Japan.

Some researchers suggest that karoshi may typical of a new class of occupational disorders that the Japanese refer to as gourika-byou or "diseases of rationalization [15]." Other such disorders include occupational cervicobrachial disorders (OCD, referred to as RSI or CTD in the United States), or vibratory white fingers (VWF). The large corporations and the state have refused to compensate most victims of these disorders on the grounds that these conditions were unavoidable due to the requirements of improved productivity, or that work as a cause of these disorders has not been proved. Yet, more than 6,000 of 40,000 telephone operators of National Telephone and Telegram suffered from OCD [16], and more than 3,000 of 20,000 chain-saw operators working for the National Forestry Service suffered from VWF from the late 1960s to 1970s [17].

If karoshi is a consequence of the rationalization of production methods in late 20th Century Japan, what is it about this process that engenders risk for sudden death? Some Japanese researchers have argued that the source of the problem might reside in the very structure of Japanese Production Management (JPM) itself. They assert that this is due to the fact that JPM involves much more than just designing and producing the highest quality product or service. It actually focuses on reducing the cost of labor through the elimination of what is referred to as "waste". Waste is defined in JPM as anything that is not absolutely essential to production. All costs associated with non-value-added functions are considered a form of waste that should be eliminated, whether it involves buffers between operations, slack time, waiting time, walking time, holidays and vacations, resting time, walking space at work stations, or, more generally, indirect labor such as skilled trades and maintenance workers. Rest time breaks, bathroom breaks, or time to wipe away sweat are regarded as waste. A night without operation is also waste. Much of the waste reduction effort involves a detailed look at jobs, work processes, and work areas to rid them of non-value-added operations and to achieve cost-cutting, worker reductions, and a tighter work effort. In this sense, JPM is an extension, even an intensification of Tayloristic, scientific management techniques into every aspect of work organization.

Working Hours

This process of work intensification has resulted in night shift work, increased scheduled and unscheduled overtime and holiday work, unpaid "voluntary" work for suggestion programs, and formal and informal functions during off-work time. A low base pay forces workers to work hard to get extra benefits. Low allowances for overtime, night shifts, etc., drive workers to work longer hours and more nights and holidays. Both white- and blue-collar workers have to do homework, so-called furoshiki zangyou (wrapped work).

Many workers manage their daily family budget only by depending on overtime and night-shift wages. In addition to homework, they must also deal with overcrowded commuting to and from industrialized cities, normally commuting over one hour each way because they can only afford inexpensive housing in the outlying suburbs.

In Japan, the sheer magnitude of working hours has been suggested as one of the possible causes of karoshi. Japan has much longer working hours than any other industrialized country. We sometimes forget the historical importance of working hours – both as an exposure characteristic, and as an issue that generated enormous political interest on the part of the 19th century working class movement. In June 1863, some London newspapers reported that a 20-year-old female garment worker died from "simple overwork" after working days averaging 16.5 hours [18]. In those times, annual working hours for the United Kingdom and United States were around 3,500 hours, assuming a 52-week work year [19]. The political actions of the labor movement in these countries forced a substantial decrease in the number of working hours – even before medical science proved its necessity. Shor [19] notes the comparatively recent problem of longer and longer working hours in the United States -- although these are still much less than is usual in Japan.

Japanese working hours have remained the same or tended to increase since 1975 as measured by overtime, holiday and vacation work, number of vacations and time off with pay, and the five-day work week [20]. Working hours have largely decreased since World War II in the Western countries. International comparative statistics show that the [annual] working hours of Japan are the longest (2,159 hours in 1989) among the industrialized countries. The Japanese still work more hours than Americans -- about 236 hours per year on average according to an International Labor Organization study. In Japan, the number of male workers who work more than 3,120 hours a year--that is more than 60 hours a week on average--has increased since 1975 when the number was around 3 million, or 15 percent of employed male workers. In 1988 it reached around 7 million, or 24 percent [21].

Recently, the national government took advantage of international trade pressure to change the law, making it more convenient for corporations to manage long working hours more cost-effectively. Unpaid and so-called voluntary overtime work has become very common. Japanese Labor Standards do not limit overtime work as long as there is a collective agreement between labor and management. The hours and proportion of overtime are greater in large compared to small firms. Most overtime has been regularly included in the work day under the collective agreement with cooperative enterprise unions. The minimum standard of extra pay for overtime is as low as 25-percent of the normal wage. It was symbolic of the governmental support for overtime when the Supreme Court recently judged the firing of a worker who for the first time refused overtime to be legal [22].

The Supreme Court made this judgment on November 18, 1991: A worker at Hitachi Company was ordered to do more than 5 hours of overtime work just 15 minutes before the end of work in 1967. Because he had a previous engagement to meet friends, he refused the overtime work. He completed the assigned work the next day by working overtime until 9:00 p.m. The Hitachi Company asked him to change his thinking, but when the company realized he would not, they gave him the disciplinary dismissal.

Most observers outside Japan have the misconception that Japanese workers obtain large incomes by hard work with much overtime; however, the ratio of labor cost to actual working hours is much lower than in the United States and other industrialized countries [23,24]. In 1986, the wage rate ratio of the United States as compared to Japan was 136 to 100. Furthermore, when comparing the purchasing power parity in relation to the consumer price level, the Japanese level still falls behind some European countries


People may ask: "Why do the Japanese work themselves to death. Why don't they just take a rest before they collapse?" Cultural differences are often invoked to explain why the Japanese ‘do this to themselves.’ Another explanation for why Japanese workers immerse themselves in their jobs is that it is a customary practice produced by long-term international competition [25]. Still others suggest that Japanese management has been able to instill a managerial orientation in all employees, including blue collar workers by attaching more importance to the overall adaptability to the needs of the firm than to specialization into a specific skill or craft [26].

But case studies indicate that the main reason for over-work is rooted in the very nature of the Japanese Production Management system itself. Japanese corporate society has been infused with JPM ideology in such a way that working 24-hours a day is seen as exemplary, even idealistic behavior. The social atmosphere is such that a pharmaceutical company advertised a new beverage in a television commercial with the song "Can you fight 24 hours for your corporation?"

Japanese production management has been discussed in terms of rationalization, the productivity improvement movement, Kaizen [27], Kanban [27], JIT (just-in-time system), small group activities, QC (quality control), TQC (total quality control), TQM (total quality management), ZD (zero defect), suggestion systems, and so on, based on the historical period of time, the corporation, or the national context. In the West it is increasingly referred to as ‘lean production.’ JPM originated from a type of industrial engineering imported from the United States that had been inspired in the 1940s and 1950s by Deming, Juran, and others [28,29]. In those years, Japan's major production resource was cheap labor. Japanese corporations applied existing theories and techniques to organize this cheap labor more efficiently. The heart of this system can be understood by the Japanese term Kaizen, as Imai has stated [27]:

The essence of most 'uniquely Japanese' management practices--be they productivity improvement, TQC activities, QC circles, or labor relations--can be reduced to one word: Kaizen. In this context, using the term Kaizen paints a far clearer picture of what has been going on in Japanese industry. .... Kaizen is an umbrella concept covering most of those uniquely Japanese practices that have recently achieved such worldwide fame. These concepts have developed strategies that assure continuous improvement involving people at all levels of the organizational hierarchy.

Kaizen, "continuous improvement," depends on workers' contributions through programs such as suggestion programs or small-group activities geared to problem solving. The goal is to get workers to support cost cutting, to accept job reductions, and to participate with management in changing work processes and practices. Kaizen involves more than participation – it encourages workers to treat each other as suppliers and customers or competitors rather than as coworkers.

The combined effects of the different aspects of kaizen on karoshi is suggested by the following case study, drawn from the classic descriptive literature [6]: In 1979 the major task of a karoshi worker (who died at the age of 45 years after 13 successive duty days, including 6 successive night shifts) was assembling engine parts in the model plant under the "new producing method" at Toyo Industry Company (the new Mazda Motor Company) in Hiroshima. The line speed was 2 minutes per car; there was no difference in speed between shifts and no spare time which meant this worker assembled engine parts for 250 cars every 500 minutes. The production method at Toyo involved (1) synchronized production: "just in time", no pool of parts and no waste; (2) value organization: to identify the spare time used by each individual worker so as to identify waste time; and (3) supplement production: to get the minimum necessary parts from suppliers and subcontractors in order to reduce stock.

Two methods were used: One method focused on revealing any ‘waste time’ by having workers with any spare time to stand conspicuously and simply do nothing. This meant that if a worker could finish his task in 40 seconds rather than the prorated 60 seconds, he would be made to stand the remaining 20 seconds. In other words, he would have to wait the 20 seconds before starting his task over again.

The second method involved a modification of the work factor system (WFS) imported from the United States. Management determined the standard time for each basic movement, measured the number of basic motions of a very skilled worker and identified the minimum number of each task. They did not factor in any safety coefficient on the final number. Under this new production method, the worker resembles a mouse running helplessly in a rotating wheel in order to avoid electric shock, rather than a working human.

According to its advocates the application of the philosophy of kaizen in JPM is manifested in many concrete ways: It organizes workers to adapt to any situation, to cooperate as a team, to become generalists, to pay attention to details, to make the best of human resources, to share all information with other workers, to manage cross-functionally, to build the system on existing technology, to cooperate cross-sectionally, and to give feedback to all other workers. One ostensible characteristic of JPM is to encourage the formation of small teams of workers. This ‘team concept’ has been widely used in many corporations inside and outside Japan.. According to a survey conducted by the Japanese Ministry of Labor, about half of companies with more than 1,000 employees have small-group activities [27]:

The small groups have a vital role in raising productivity, creating a more pleasant and meaningful work environment, and improving industrial relations. Small groups also play an important role in resolving conflict and laying the foundation for good industrial relations. The creation of sound labor-management relations in Japan often depends on building up a small core of workers at the shop floor who are able to reconcile their dual roles as loyal employees and loyal union members. The loyal employee wishes to work hand-in-hand with management to create better products and bigger profits, almost without limit.


Japanese companies inculcate in workers their role as associates of the firm, sharing the same goals as management rather than having their own distinct interests as members of a different, working class. Companies have organized many formal, informal and/or secret activities to spread the ideology that management and workers share the same fate. Corporations often fail to recognize constitutional rights, including those related to education embodied in Japan's School Education Law. Japanese sociologists of work and the labor process report that they have eroded labor unions and converted them into company tools for controlling workers through various formal and informal means [29]. Most Japanese labor unions are organized on a corporate basis. Some low level managers are organized in the company-based labor unions. Corporations have often exploited these union-member managers and structured the labor unions along the lines of corporate organizations [29]. Thus, they have been able to promote the views of management much more easily than could have occurred in other countries. Aoki calls this "Toyota's human management method" or "corporate fascism" and has characterized such labor unions as a "camouflage" [29]. The labor movement has been considerably weakened; as shown by the decrease in rates of organization and strikes.

Womack et al. have referred to JPM as "lean production" [30]. These authors suggest that in the future automotive and other manufacturing plants will have to operate on this system in order to survive. Indeed their claims of the efficacy of JPM are quite dramatic and enthusiastic, as indicated by their statement that [30]:

"Lean production is a superior way for humans to make things ... It provides more challenging and fulfilling work for employees at every level, from the factory to headquarters. It follows that the whole world should adopt lean production, and as quickly as possible."

Clearly these authors believe that they have seen the future, and they believe it works. It is interesting to note that their studies were based on the International Motor Vehicle Program of MIT between 1985 and 1990 which received $5 million in grants from auto industry itself to undertake the study. These authors advertise the myths of JPM by selecting convenient facts while ignoring other, hence become advocates for the spread of JPM (lean production) worldwide [30].

Corporations everywhere are motivated to undertake similar programs of quality management, waste elimination, and process improvement involving the workers themselves. However, most people who glorify JPM do not consider that its focus is almost entirely on what benefits the company, not on what benefits the workers. JPM essentially increases management control and undermines the independence of labor unions and the human rights of the work force. Thus JPM must use various devices to break workers collective resistance and rebuild group solidarity on the basis of management goals, a process that has been summarized by Cole from the work of Japanese scholars [31]. Corporations cannot set and attain their production goals without "camouflaged" voluntary, employee-initiated activity; small workers' groups must implement the goals whenever there is a gap between the goal and actual performance. But this is not a process of democratization, as seen in the autonomous work groups in the Nordic countries. There is little (if any) rank and file democracy in the JPM workplace. Rather, there has been a severe shift away from human and social considerations toward such goals as improved productivity and reduced turnover and absenteeism, as Gardell and others have pointed out [32]. Some Japanese scholars and labor unions have described this as the next stage in the process of rationalization within capitalist enterprises [33].

JPM and the Psychosocial Work Environment

Several recent reviews have discussed the implications of JPM or ‘lean production’ on the three psychosocial components that make up the expanded job strain model: psychological job demands, work control, and work related social support. A growing body of scientific literature suggests that workers in high demand, low control and low social support jobs are at increased risk for developing and dying of cardiovascular disease [34]. Yet the question remains: How does JPM influence the relative degree of exposure to these three key psychosocial work environment risk factors? To address this question Landsbergis, Cahill and Schnall [35], reviewed 15 separate studies where the impact of JPM on work content and job stress was examined – mainly in transplant firms in the United States and Canada [35]. The general pattern of findings across a variety of countries, and industries indicate that psychological job demands increase, and control decreases in lean production workplaces. Moreover a number of these studies also reported an increase in fatigue, stress, tension, and muscle-skeletal disorders associated with the introduction of lean production methods. The authors conclude: "Recent surveys tend to confirm some earlier case studies that lean production does create an intensified work pace and work demands, and that promised increases in decision authority and skill levels are very modest. Thus such work can be considered to have high job strain (24, page 8)." Landsbergis’ paper suggest that karoshi should really not be thought of as a solely Japanese phenomena. Workers in other countries who are exposed to a similar system of work organization and management philosophy also report stress related symptoms. It is very possible that with increased exposure time, cardiovascular and cerebrovascular outcomes may also be reported in the West. At the same time it is likely that other types of disorders that are thought to be stress related in the West, such as elevated blood pressure, digestive system disorders, work related musclo-skeletal disorders, depression, anxiety, and behavioral outcomes such as drug and alcohol use may be an understudied consequence of lean production in Japan.

The studies reviewed by Landsbergis, et al did not directly examine work related social support, the other element in the expanded Job Strain Model. It is important to distinguish the ‘team concept’ from the ‘worker’s collectivity’. As one of the authors of the present paper [36] has discussed previously, there is a considerable difference between socially engineered groups that have been constructed to maximize productivity and to maintain managerially oriented norms and values from the ‘worker’s collectivity’ which is the construction by workers themselves of social support systems that are adaptive forms of response to industrial demands and pressures. We would anticipate that lean production or JPM would tend to eliminate worker-oriented social support and collectivity – considering it either an obstacle to increased productivity or as merely a form of unnecessary ‘waste.’

The job strain model has not explicitly examined the impact of working hours, and indeed, it is rare for Western models of work environment to focus on the quantity of working hours, per se. More attention has been given to the adverse effects of rotating shift work. Several studies performed in Sweden, however, have shown that individuals exposed to extensive overtime periods demonstrated markedly elevated levels of the stress hormones – adrenaline, nor-adrenaline and cortisol [18]. The Effort -Distress Model proposed by Marianne Frankenhaeuser has identified the excretion of these hormones as part of the pathophysiological pathway leading to CHD [37]. Jobs which require prolonged effort with emotional distress -- a condition typical of intense overtime periods, places the greatest risk on the human organism for long-term functional and structural changes. These neuro-hormonal elevations, if pronounced and prolonged over time, may place the individuals exposed at greater risk for permanent pathophysiological effects on the cardiovascular system [37].


Researchers have examined the impact of changes in the labor process and its impact on health over the past three decades [34, 38]. Regardless of the conceptual model, or the measurement methods, a general consensus has emerged that the legacy of F.W. Taylor, the founder of "scientific management" has been the creation of an essentially inhuman workplace -- a work environment characterized by authoritarian supervision, a radically delimited task structure, and broken social connections between workers [39]. Many of the adverse exposure characteristics that have become accepted psychosocial risk factors -- low work control, high demands, repetitive and monotonous work, are direct and natural consequences of the managerial principals of Taylorism. JPM or "lean production" is currently being touted as the way to increase both worker empowerment and productivity -- thereby eliminating the ill effects of Taylorism [30]. Though JPM may indeed result in greater productivity over the short-run, this may come at an even greater cost to the work force. Very little of the current international research on JPM has examined its health impact in either the Japanese work force or in Europe or the United States. Although a number of critics have called JPM and lean production "Management by Stress" [40], to date, there have been no well conducted epidemiological studies that explicitly examine the health impact of JPM in comparison to either Taylorism or more democratic forms of work organization. The survey research that has been performed does indicate that workers in lean production transplants in North America report that they believe that they work substantially harder than workers in traditional manufacturing plants (and, their managers agree with this assessment) [36].

The results of Japanese studies that have examined the association between job strain and adverse health outcomes are mixed and rather inconclusive [41-43] Although few epidemiological studies have actually been performed, those that have did not use measurement methods that would allow a real test of the job strain hypothesis. One case-control study of coronary heart disease patients reported higher demands among cases compared to controls but failed to examine the effects of work control [41]. More recently, a study of hypertension in Japan, actually reported a negative association between job strain and blood pressure [42]. It has only been recently that measures have been developed and applied in Japan that will permit standardized international comparisons in the future [43].

Yet, it is possible that the measurement scales developed to test the Demand-Control-Support model may not able to capture what is particularly stressful about JPM. Many of the current work content instruments were developed to examine the characteristics of Taylorism, where there was little, if any, participation in decision making, and very little group work. Without understanding and measuring the organizational context of decision making and group activities, it is likely that current instruments will over-estimate the amount of work control and social support employees actually have in JPM firms. There is a great need to study the health consequences of JPM more concretely, with specifically designed measures, and in an epidemiological rigorous manner through international comparative research.

The myth of JPM and "lean production" as the inevitable wave of the future has been widely promoted throughout the world by both the Japanese government and corporations and their followers, as observed at the Second Meeting of the Panel Forum on Labor in a Changing World Economy held by the International Labor Organization [44]. There has been little discussion of the occupational health consequences of JPM in the international research community.

In the future it will be necessary to study Japanese labor-management practice itself by a social epidemiology that utilizes an international comparative approach. The risk factors in JPM work organizations should be studied both in terms of work intensity, the magnitude of working hours, and its effects on skill discretion, decision authority and workers’ social support.

The real danger is that JPM may be a kind of work organization "Trojan Horse." Since it is often posed as a seemingly progressive change away from the authoritarian management style of Taylor, and towards participation and team work, its anti-democratic implications have been well disguised. Health researchers and occupational health professionals should view the current popularity of JPM/lean production techniques with some skepticism. Until well designed and conducted epidemiological studies that examine the health impact of JPM are available, the Japanese phenomena of karoshi should serve as a warning.


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