Unexpected Natural Death among Korean Workers

Transcription

1 J Occup Health 1999; 41: Journal of Occupational Health Unexpected Natural Death among Korean Workers Jungsun PARK 1, Young-Sook CHO 1, Kwan-Hyung YI 1, Kyung-Yong RHEE 1, Yangho KIM 2 and Young-Hahn MOON 1 1 Industrial Safety and Health Research Institute, Korea Industrial Safety Corporation (KISCO) 2 Department of Occupational and Environmental Medicine, Ulsan University Hospital Abstract: Unexpected Natural Death among Korean Workers: Jungsun PARK, et al. Industrial Safety and Health Research Institute, Korea Industrial Safety Corporation Even though workers deaths can be compensated for in Korea if work stress is substantiated as a cause, neither a definition nor a measure has been officially provided to verify occupational stress or overwork. This study was carried out to identify epidemiological characteristics and components of work stress associated with workers death. All the records of claims for compensation during were reviewed to select only the cases of natural death. A descriptive study on the characteristics of workers natural death and a matched case-control study on stress components were carried out. Cerebrovascular accidents was the commonest cause of death (47.3%) in claims for compensation due to work stress, and coronary artery diseases took second place (29.9%). Sudden death occurring within 24 h after the attack comprised about 1/2 of the total cases. The attack took place most frequently at the workplace and most often during work. When work stress was classified and observed in four categories: sudden physical exertion, sudden psychologic excitement, prolongation of work time, and change in responsibility, only physical exertion within 24 h before the onset of symptoms proved to be significantly associated with workers unexpected natural death. (J Occup Health 1999; 41: ) Key words: Sudden death, Unexpected natural death, Karoshi, Workers compensation, Work stress Recently, unexpected natural death has become the leading cause of workers compensated work-related death in Korea. It is generally considered that cardiovascular disorder is the commonest cause of sudden unexpected death 1). Occupational stress can cause sudden Received Apr 30, 1999; Accepted July 9, 1999 Correspondence to: J. Park, Industrial Health Research Institute, KISCO, 34-6 Kusan-Dong, Pupyeong-Ku, Inchon , South Korea unexpected death in a person who had been suffering from an aggravated preexisting condition such as hypertensive or arteriosclerotic diseases. The Korean government has compensated the cases of cerebrovascular disease and cardiovascular disease due to overwork or occupational stress, but neither definition nor measure has been officially provided to verify occupational stress or overwork, so that the prevention of, as well as compensation for workers occupational stress-related cardiovascular attacks, cannot be carried out efficiently. Until now few epidemiological, analytical studies on sudden unexpected death in Korea have been carried out on the working population; so we started our research to get an overview of unexpected natural death among Korean workers employed in workplaces with five or more employees. The objectives of this study were 1) to describe the epidemiological characteristics of those who claimed compensation for unexpected natural death; 2) to identify components of work-related stress associated with workers death; and 3) to contribute to the prevention of unexpected death among middle-aged workers. Methods Claim System in Korea The Industrial Accident Compensation Insurance Law was enacted in 1963 to provide necessary insurance benefits to injured workers and also give them prompt and fair protection against injury, disease, disability and death. The insurance would grant short or long-term benefits, to promote the rehabilitation of workers who suffer injury or disease resulting from the employment and to assist the injured workers and their families, and thereby to promote the welfare of workers. The insurance program is administered by the Ministry of Labor and all enterprises which fit the governmental criteria with some exceptions are required to join this program. An exception is firms which employ less than five workers 2). When a worker dies of work-related injury or disease, his or her family can put in a claim for workers compensation arbitrarily to the local office of the Korean Labor Welfare

2 Jungsun PARK, et al.: Unexpected Natural Death among Korean Workers 239 Corporation under the Ministry of Labor. Descriptive Epidemiologic Study We defined unexpected natural death as an unaccidental death occurring without warning in a person who had had no restrictions on his daily working activities prior to the onset of symptoms. Warning in this setting means severe subjective symptoms or objective signs, which could have made him or her see the doctor. Unexpected natural death is unrelated to the time from the onset of disease to death, which time mainly depends on various factors such as appropriate first aid measures, the referral system, and level of care in emergency medicine in cerebro- and cardiovascular diseases. We therefore adopted the term unexpected natural death even though sudden death is a world standard technical term well defined as internal death within 24 h from the onset of the event 3) and generally accepted and used throughout the world. Sudden death is included in unexpected natural death not only limited to 24 h after the attack. Firstly, all the records of claims for workers compensation during were reviewed to select only natural death with the criteria for internal death, and to select only unexpected death with the criteria for warning. We then carried out a descriptive study on the characteristics of workers unexpected natural death based on information from the records of compensation claims such as death certificates, application forms for compensation, investigation records of death due to industrial accidents, and their past working records, etc. Claimed cases of unexpected natural death therefore included not only all of the official registered compensated cases, but also uncompensated cases. We prepared a questionnaire of our own and included in if the contents of records of compensation claims. It included items about demographic characteristics (age, sex, marital status, education), information on the attack (the time and place of the attack, symptoms of the attack, time of death, place of death, and cause of death, etc.), information from physical examination (body weight, height, blood pressure, health problems), lifestyle (alcohol consumption, smoking habit, physical exercise), and the working conditions (occupation, shift work). We especially tried to get information about the working conditions which caused the attack through all available documents such as sudden heavy physical activity related to work and which preceded the attack within 24 h, sudden severe emotional stress related to work and which preceded the attack within 24 h, change of work load which preceded the attack within a week, and change of work content which preceded the attack within a month. The underlying causes and the immediate causes of death of all claimed cases were reviewed and corrected where the underlying causes and the immediate causes of death were reversed by two medical doctors. A matched -Control Study We tried to find why some workers died unexpectedly, but others are still alive in spite of working in the same workplace. So we carried out a matched case-control study on the work-related stress component. The number of matched samples from each provincial area were determined based upon the number of claimed cases in each provincial area. First of all, case samples in each provincial area were selected randomly with a proportional sampling rate of 10% by area and industry, the process of which included the making of lists of random sample numbers. A matched control for each of the cases was selected according to sex and age (equal or with a difference of less than 5 yr) from workers in the same workplace (individual 1:1 matching), but not matched for other factors such as smoking or alcohol consumption. The selection of each control was then conducted under clear instructions. Face-to-face interviews for control group lasted from 20 to 30 min. The interview was conducted in a standard manner by 4 well trained interviewers. Interviews were periodically monitored for quality control. The questionnaire included items about demographic characteristics (age, sex, marital status, education), information on physical examination (body weight, height, blood pressure), lifestyle (alcohol consumption, smoking habit, physical exercise), and the working conditions (occupation, shiftwork, heavy physical activities or emotional stress related to the worker s duties on the survey day, change of work load within a week before the survey day, change of work content within a month before the survey day). McNemar test was performed for matched-pair analysis. Results The sex and age distribution of the death cases claimed during , the 2 yr of observation, are given in Table 1. The cases claimed were for 812 males (90.8%) Table 1. Sex and age distribution of the death cases Demographic No. of s (%) Characteristics Sex Male 812 ( 90.8) Female 82 ( 9.2) Total 894 (100.0) Age ( 4.6) ( 16.3) ( 30.6) ( 34.4) 60 over 126 ( 14.1) Total 894 (100.0)

3 240 J Occup Health, Vol. 41, 1999 Table 2. Industry and occupation distribution of the death cases Industry and Occupation No. of s (A) No. of Workers (B) A/B 100,000 Industry Mining and Quarrying 7 40, Manufacturing 314 3,084, Electricity/Gas 14 53, Water supply Construction 156 1,978, Transportation/ , Storage Communication Other Community/ 187 1,452, Social and Personal Service Activities Total 806 7,250,754* 1) 1.12 Occupation Professional and , Technological Workers Clerical and related 162 1,655, Workers Sales Workers , Service Workers , Production & related 431 1,964, Workers/Transport Equipment Operators/Laborers Others 4 2, Total 812 4,534,988* 2) Source: *1) Total workers employed in workplaces with five or more employees by industry; Ministry of Labour Report on Establishment Labour Conditions Survey, *2) Total workers employed in workplaces with 10 or more employees by industry; Ministry of Labour Report on Wage Strucuture Survey, and 82 females (9.2%). The percentage distributions by age groups of 50 59, 40 49, 30 39, above 60, and 20 29, was 34.4%, 30.6%, 16.3%, 14.1%, and 4.6%, respectively. Men in their forties and fifties were therefore predominant. Table 2 shows industry and occupation distribution of the death cases claimed during According to industrial classification, the proportion among total claimed cases was high for the manufacturing industry, but the incidence rate was highest for the transportation/ storage/communication industry. According to occupational classification, the proportion among total claimed cases was high for production and related workers/transport equipment operators/laborers, but the incidence rate was highest for service workers. The attack causing unexpected natural death took place at the workplace (70.9%). As shown in Table 3, daily Table 3. Daily activity at the time when the attack occurred Situation No. of cases (%) At work 197 ( 58.9) Taking a rest 47 ( 14.1) Moving from place to place 30 ( 9.0) Sleeping at night 25 ( 7.5) Taking a bath 12 ( 3.6) Having a meal 8 ( 2.4) Physical exercise 4 ( 1.2) While in the lavatory 3 ( 0.9) Others 8 ( 2.4) Total 481 (100.0)

4 Jungsun PARK, et al.: Unexpected Natural Death among Korean Workers 241 Table 4. The cause of death Cause of death No. of cases (%) Cardiovascular diseases 427 ( 47.3) Ischemic heart diseases 270 ( 29.9) Unknown sudden death 157 ( 17.4) Others 43 ( 4.8) Unclassifiable 6 ( 0.7) Total 903 (100.0) Table 5. Time lapse between initial attack and death Time lag No. of cases (%) Less than 1 h 261 ( 28) 1 24 h 215 ( 23) 1 day 1 week 191 ( 20) More than 1 week 194 ( 21) Unknown 74 ( 8) Total 935 (100) Table 6. The distribution of 477 death cases by the cause of death and age group unit: person (%) Age Cerebrovascular Ischemic heart Unknown Others Total diseases diseases sudden death (19.0) 6 (28.6) 9 (42.9) 2 (9.5) 21 (100.0) (48.0) 17 (22.7) 17 (22.7) 5 (6.4) 75 (100.0) (46.4) 41 (29.3) 24 (17.1) 10 (7.1) 140 (100.0) (43.2) 73 (41.5) 21 (11.9) 6 (3.4) 176 (100.0) (44.6) 25 (38.5) 9 (13.8) 2 (3.1) 65 (100.0) Total 210 (44.0) 162 (34.0) 80 (16.8) 25 (5.2) 477 (100.0) activities at the time when the attacks occurred are most frequently at work (58.9%), and then taking a bath (14.1%), moving from place to place (9.0%), sleeping at night (7.5%), in that order. As Table 4 shows, the major cause of death in the 903 cases was cerebrovascular disease (47.3%) and then ischemic heart disease (29.9%). Table 5 shows the time lapse between initial attack and death. Among claimed cases due to unexpected natural death, sudden deaths within 24 h of the attack comprised 51%. This figure can be divided into 28% for deaths within an hour of an attack and 23% for the rest. The peak time of attacks was noon to 4:00 P.M., and then 8:00 A.M. to noon. Attacks were rare between midnight and 4:00 A.M. Unexpected natural death tended to occur more on Wednesday or Friday, and less on Thursday, Saturday, or Sunday. The peak month for attacks was September, followed by February and October. On the other hand, the incidence of attacks was lowest in January. Table 6 shows the cause of death by age group. The proportion of cerebrovascular accidents tended to increase with age. And the proportion of unknown sudden deaths tended to occur more amongst the lower age groups. Table 7 summarize the matched comparison of unexpected natural death cases and living controls with regard to the experience of various kinds of work-related stresses. Work-related stress was divided into sudden physical exertion, sudden emotional excitement, change of work load, and change of work content. Sudden physical exertion within 24 h before the attack was high significantly associated with unexpected natural death. And sudden emotional excitement within 24 h before the attack was not associated with unexpected natural death. Mental stress due to change in work load within a week before the attack was less significantly associated with unexpected natural death. And mental stress due to a change in work content within a month before the attack was significantly associated with unexpected natural death. Discussion Of the relationships between occupational stress and cardiovascular diseases, Uehata suggested in his case study that the cases of cardiovascular attack among middle-aged workers who claimed workers compensation mostly consisted of male workers who worked for long hours and had other stressful overload and these working situations aggravated their unhealthy life habits, resulting in the attacks triggered by minor work-related troubles or events 4). Cooper also suggested in his review that various types of stressors at work, such as quantitative and qualitative overload, role ambiguity or conflict, over- or under- promotion, and impact of poor relationships with reference to these stressors were associated with heart diseases 5). On the other hand, Karasek suggested that high psychological work demands and low decision latitude on the job may be associated

5 242 J Occup Health, Vol. 41, 1999 Table 7. Matched comparison of experience of work-related stress in cases and controls: McNemar Test Sudden heavy physical activity 1) with the development of a coronary heart disease, and these work characteristics might be related to the incidence of myocardial infarction as a single risk factor 6). Moreover, Jenkins suggested that people with a type A behavioral pattern known as a risk factor for ischemic heart disease, characterized by extremes of competitiveness, striving for achievement and aggressiveness, could often be deeply involved and committed to their work, and other aspects of their lives relatively neglected 7). The WHO committee report on work-related diseases, showing kinds of concerns, emphasizes that short-term periods of stress bring on temporary bouts of high blood pressure, and when such stressful conditions become chronic, they may lead to continuous hypertension 8). In the present study, the incidence rate of unexpected natural death was highest for the electricity/gas water supply industries, in which workers tend to do a lot of shift work or night work. The suggestion that shift-work Have Control Not have Total Sudden severe emotional stress 2) Have Control Not have Total Latest change in work load 3) Have Control Not have Total Latest change in work content 4) Have Control Not have Total ) sudden heavy physical activity related to work and preceding the attack within 24 h. 2) sudden severe emotional stress related to work and preceding the attack within 24 h. 3) change in work load preceding the attack within a week. 4) change in work content preceding the attack within a month. can be a risk factor for unexpected natural death in the present study is also seen in other papers 9, 10). By occupation, the incidence rate was highest for service workers. A large proportion of unexpected natural deaths have been attributed to coronary artery disease (mostly atherosclerotic ischemic heart disease) among males 30 and older 1), but Uehata reported that among 203 Karoshi consultation cases collected for sixteen years from 1974 to 1990, two thirds were strokes including subarachnoidal bleeding, cerebral bleeding and cerebral infarction. He also reported that the proportion of sudden deaths which occurred within 24 h of the initial attack was 78.2% of all cases 4). The results of the present study support the findings of Uehata s study that show most of the causes of unexpected natural deaths were stroke, and most unexpected natural deaths occurred within 24 h of the initial attack. Some of the causes in the abovementioned results can probably be presumed. To be work-related, the accident must: (1) arise out of the employment, and (2) happen in the course of the employment. The arising-out-of-the-employment requirement usually requires a sufficiently close relationship between the injury and the nature of the employment. The in-the-course-of-theemployment requirement inquiry as to whether the accident occurred within the time, place, and circumstances of the employment. Employees injured off the employer s premises are generally outside the course of the employment. In Korea the tendency has been for work-related attacks to be easily approved if the attack occurred during work at the workplace, because the in-the-course-of-the-employment requirement has been emphasized in Korean criteria for recognizing occupational cerebrovascular or cardiovascular diseases. Families of the deceased tend not to claim cases which are decided to have occurred outside the workplace or not during work time, shown in the present report. In addition, autopsies have rarely been performed in Korea, and it is not easy to determine the cause of unexpected natural death due to an acute heart attack without an autopsy.

6 Jungsun PARK, et al.: Unexpected Natural Death among Korean Workers 243 In this study, we matched the workplace of the case and the control because ordinary working conditions are regarded as a confounding factor in the occurrence of unexpected natural death, and matching with a co-worker made it possible to adjust for the differences in work style and the work environment. We tried to find differences between cases and controls in working conditions after matching for sex, age, and ordinary working conditions, and to get information on the factors causing the attack. The matched comparison of cases and controls showed that unexpected natural death among Korean workers was associated with work-related stress such as heavy physical activity related to work within 24 h of the attack or a change in work content within a month before the attack, so that unexpected natural death might be influenced by work-related stress 4, 5, 11). In general, high blood pressure (especially systolic pressure), diabetes mellitus, and EKG abnormality (left ventricular hypertrophy or ST-T change), smoking history and serum cholesterol have been accepted as risk factors for sudden death in many reports 12 18), but such information was not collected in the present study. There are some limitations to this study. One is the selection bias. Our study subject was compensated claimed cases. Claimed cases might be self-screened before the family claimed. The other is the information bias. The authors gathered the information on the deceased from documents submitted for a claim only, though living controls were interviewed directly. So we lacked information on laboratory data after the attack, the personal medical history, especially on hypertension or diabetes mellitus, and risk factors for cardiovascular diseases such as smoking, EKG abnormality, serum cholesterol, and alcohol consumption for unexpected natural death cases. There may also be overestimation of work-related stress as a cause of death, because the cause is investigated after death, and work-related stress might be carefully looked for. In conclusion, unexpected natural death might be influenced by work-related stress. More experimental and epidemiological research must be carried out to identify the exact risk factors or causes of cerebrovascular or cardiovascular attack for prevention of unexpected natural death among middle-aged workers. References 1) Kwon I. Analysis of Sudden Unexpected Natural Death in Legal Autopsy during Annual Report of National Institute of Scientific Investigation. 1995; 27: (in Korean). 2) Ministry of Labor. Labour Laws of Korea, Ministry of Labor Publication no ) WHO Exp. Committee. Sudden cardiac death. Geneva: World Health Organization, (WHO Tech Rep Ser 726: 5 25). 4) Uehata T. study of Karoshi due to work-related cardiovascular attacks in Japan. In: Finnish Institute of Occupational Health ed. Proceedings of the International Symposium on New Epidemics in Occupational Health, Helsinki: Finnish Institute of Occupational Health, 1994: ) Cooper CL, Marshal J. Occupational sources of stress, a review of the literature relating to coronary heart disease and mental ill health. J Occup Psychol 1976; 49; ) Karasek R, Baker D, Marxer F, et al. Job decision latitude, job demands and cardiovascular disease. Am J Public Health 1981; 71 (7): ) Jenkins CD. Psychologic and social precursors of coronary disease (II). New Eng J Med 1971; 284 (6): ) WHO Exp. Committee. Identification and control of work-related disease. Geneva: World Health Organization, (WHO Tech Rep Ser 714: 22). 9) Akerstedt T, Knutsson A, Alfredsson L, et al. Shift work and cardiovascular disease. Scand J Work Environ Health 1984; 10: ) Kristensen TS. Cardiovascular disease and the work environment A critical review of the epidemiologic literature on nonchemical factors. Scand J Work Environ Health 1989; 15: ) Uehata T. Long working hours and occupational stressrelated cardiovascular attacks among middle-aged workers in Japan. J Hum Ergol 1991; 20: ) Hoshuyama T, Saeki S, Takahashi K, et al. A Descriptive Epidemiology on Sudden Death among Workers. J UOEH 1992; 14 (3): (in Japanese). 13) Hoshuyama T, Saeki S, Takahashi K, et al. A Matched -Control Study on Sudden Unexpected Death among Japanese Workers. J Epidemiol 1993; 3: ) Kiryu Y, Suzuki S, Hosogai H, et al. A case-control study on the risk factors of sudden death. Jpn J Ind Health 1994; 36: ) Kannel WB, Gagnon DR, Cupples LA. Epidemiology of sudden coronary death: population at risk. Can J Cardiol 1990; 6: ) Kannel WB, Plehn JF, Cupples LA. Cardiac failure and sudden death in the Framingham study. Am Heart J 1988; 115: ) Kreger BE, Cupples LA, Kannel WB. The electrocardiogram in prediction of sudden death: Framingham study experience. Am Heart J 1987; 113: ) Kagan A, Yano K, Reed DM, et al. Predictors of sudden cardiac death among Hawaiian-Japanese men. Am J Epidemiol 1989; 130: