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Oversigtsartikel om skæve arbejdstider og hjertesygdom

Oversigtsartikel om skæve arbejdstider og hjertesygdom

Artikler der kommer til at indgå i oversigten

Alfredsson L, Theorell T. Job characteristics of occupations and myocardial infarction risk: effect of possible confounding factors. Soc Sci Med 1983;17 (20):1497-503.

In this paper some previously found associations between psychosocial occupational characteristics and myocardial infarction (MI) risk are scrutinized regarding confounding effects. Standardized occupational characteristics were obtained for 118 occupational groups by means of a nation wide interview survey (3876 men). Possible confounding factors available were smoking, low level of education, high proportion of immigrants (mainly of Finnish origin) and heavy lifting. The standardized characteristics were utilized in a case-control study of 1216 men 40-64 years of age, living in the Stockholm County. It was concluded that occupations characterized by both high demand and at the same time small possibility of control or growth ('strain') are associated with an elevated MI risk regardless of the confounding factors. Taking each of the confounding factors into account the risk of developing MI for men aged 40-54 years employed in these strenuous occupations is about twice as high as for those employed in other occupations.
Alfredsson L, Spetz C-L, Theorell T. Type of occupation and near-future hospitalization for myocardial infarction and some other diagnosis. Int J Epidemiol 1985;14 (3):378-88.

Using three different registers a cohort study was undertaken to describe the relationship between type of occupation and hospitalization. A total of 958 096 subjects aged 20-64 years were followed-up for one year regarding inpatient care. Several significant associations between type of occupation and incidence of hospitalization for different diagnoses were observed. Male subjects employed in occupations where a high proportion reported a combination of hectic work and few possibilities to learn new things were more frequently hospitalized for myocardial infarction than other working men. The relative 'hospitalization' ratio for men 20-54 years of age in these strenuous occupations was estimated as 1.6 with a 95% confidence interval of 1.3-1.9. For women, the relative 'hospitalization' ratio in the ages 20-64 in occupations where a high proportion reported a combination of hectic and monotonous work was estimated as 1.6 with a 95% confidence interval of 1.1-2.3. Both these associations were statistically significant even after controlling for 12 possible confounding factors
Bøggild H, Suadicani P, Hein HO, et al. Shift work, social class, and ischaemic heart disease in middle aged and elderly men; a 22 year follow up in the Copenhagen Male Study. Occup Environ Med 1999;56 (Sep.):640-5.

OBJECTIVES: Shift work has been associated with an increased risk of ischaemic heart disease (IHD). Most published studies have had potential problems with confounding by social class. This study explores shift work as a risk factor for IHD after controlling for social class. METHODS: The Copenhagen male study is a prospective cohort study established in 1970-1 comprising 5249 men aged 40-59. Information obtained included working time, social class, and risk factors for IHD. A second baseline was obtained in 1985-6. The cohort was followed up for 22 years through hospital discharge registers for IHD, and cause of death was recovered from death certificates. RESULTS: One fifth of the cohort was shift working at entry with a significantly larger proportion of shift workers in lower social classes. Risk of IHD and all cause mortality over 22 years, adjusted for age only, for age and social class, and finally for age, social class, smoking, fitness, height, weight, and sleep disturbances, did not differ between shift and day workers. The relative risk of IHD, adjusted for age and social class was 1.0 (95% confidence interval (95% CI) 0.9-1.2). Men being shift workers in both 1971 and 1985 had the same risk as ex-shift workers in an 8 years follow up from the 1985-6 baseline. CONCLUSIONS: The present study questions shift work as an independent risk factor for IHD. The results of the study emphasise the importance of controlling adequately for the interplay of shift work and social class
Fujino Y, Iso H, Tamakoshi A, et al. A Prospective Cohort Study of Shift Work and Risk of Ischemic Heart Disease in Japanese Male Workers. Am J Epidemiol 2006;e-pub.

This study prospectively examined the association between shift work and the risk of ischemic heart disease among Japanese male workers. A baseline survey, which involved 110,792 inhabitants (age range: 40-79 years) from 45 areas throughout Japan, was conducted between 1988 and 1990. The causes of death were identified from death certificates. The analysis was restricted to 17,649 men (age range: 40-59 years) who were employed at the time of the baseline survey. All subjects were asked to indicate the most regular shift work that they had undertaken previously: day work, rotating-shift work, or fixed-night work. The Cox proportional hazards model was used to estimate the risks of shift work for ischemic heart disease. During the 233,869 person-years of follow-up, a total of 1,363 deaths were recorded, 86 of which were due to ischemic heart disease. Compared with the day workers, the rotating-shift workers had a significantly higher risk of death due to ischemic heart disease (relative risk = 2.32, 95% confidence interval: 1.37, 3.95; p = 0.002), whereas fixed-night work was not associated with ischemic heart disease (relative risk = 1.23, 95% confidence interval: 0.49, 3.10; p = 0.658). In addition, subjects with coronary risk factors, such as hypertension, overweight, habitual alcohol consumption, and smoking, were highly susceptible to the effect of rotating-shift work on the risk of death due to ischemic heart disease
Hedberg GE, Jacobsson KA, Janlert U, et al. Risk indicators of ischaemic heart disease among male professional drivers in Sweden. Scand J Work Environ Health 1993;19:326-33.

Abstract: Possible risk indicators of ischemic heart disease relevant to the occupation of professional driving were identified in a cohort of 440 professional drivers and 1000 referents from the Swedish countries of Vasterbotten and Norrbotten. The subjects were randomly selected. Data on cardiovascular risk indicators were collected from questionnaires, blood pressure measurements, serum lipid levels, height, and weight. The results showed that significantly more drivers than referents were overweight, smokers, and shift workers; were sedentary in their leisure time; and had a work situation characterized by high demands, low decision latitude, and low social support. There were no significant differences concerning blood pressure and serum lipid levels. The odds ratio for having a high score on a cardiovascular risk index was 3.18 (95% confidence interval 2.41-4.20) for the drivers when they were compared with the referents. When adjusted for age, heredity, shift work, educational level, marital status, and working class, the odds ratio was 2.34 (95% confidence interval 1.70-3.21).
Karlsson B, Alfredsson L, Knutsson A, et al. Total mortality and cause-specific mortality of Swedish shift- and dayworkers in the pulp and paper industry in 1952-2001. Scand J Work Environ Health 2005;31 (1):4-10.

OBJECTIVES: The study investigated the relationship between shiftwork and mortality, both total mortality and cause-specific mortality from coronary heart disease (CHD), stroke, and diabetes. Methods The cohort consisted of 2354 shiftworkers and 3088 dayworkers in two pulp and paper manufacturing plants. The mortality of the cohort was monitored from 1 January 1952 to 31 December 2001 by linkage to the national Cause of Death Register. Groups of workers defined by different durations of shiftwork exposure were compared with dayworkers by calculating standardized relative rates (SRR). RESULTS: Death due to any cause (total mortality) was not higher among the shiftworkers than among the dayworkers [SRR 1.02, 95% confidence interval (95% CI) 0.93-1.11]. A longer duration of shiftwork was associated with an increased risk of CHD, and shiftworkers with >30 years of shiftwork had the highest risk of CHD (SRR 1.24, 95% CI 1.04-1.49) Diabetes was more common as the number of shift years of exposure increased [b(linear coefficient) = 4.14 x 10(-5), 95% CI 2.46 x 10(-5) -5.81 x 10(-5)]. Compared with dayworkers, shiftworkers had a greater risk of death due to stroke (SRR 1.56, 95% CI 0.98-2.51). CONCLUSIONS: In the present study, no general increase in mortality was observed among shiftworkers when they were compared with dayworkers. However, the results demonstrate an increased mortality from CHD among shiftworkers with a long duration of shiftwork exposure. Mortality due to diabetes also increased as the number of shift years and mortality due to ischemic stroke in shiftworkers increased.
Kawachi I, Colditz GA, Stampfer MJ, et al. Prospective study of shift work and risk of coronary heart disease in women. Circulation 1995;92 (11):3178-82.

BACKGROUND: The purpose of this study was to examine prospectively the relation of shift work to risk of coronary heart disease (CHD) in a cohort of women. METHODS AND RESULTS: An ongoing prospective cohort of US female nurses, in whom we assessed (in 1988) the total number of years during which they worked rotating night shifts (at least three nights per month in addition to day and evening shifts), included 79,109 women, 42 to 67 years old in 1988, who were free of diagnosed CHD and stroke. Incident CHD was defined as nonfatal myocardial infarction and fatal CHD. During 4 years of follow-up (1988 to 1992), 292 cases of incident CHD (248 nonfatal myocardial infarction and 44 fatal CHD) occurred. The age-adjusted relative risk of CHD was 1.38 (95% CI, 1.08 to 1.76) in women who reported ever doing shift work compared with those who had never done so. The excess risk persisted after adjustment for cigarette smoking and a variety of other cardiovascular risk factors. Compared with women who had never done shift work, the multivariate adjusted relative risks of CHD were 1.21 (95% CI, 0.92 to 1.59) among women reporting less than 6 years and 1.51 (95% CI, 1.12 to 2.03) among those reporting 6 or more years of rotating night shifts. CONCLUSIONS: These data are compatible with the possibility that 6 or more years of shift work may increase the risk of CHD in women
Knutsson A, Åkerstedt T, Jonsson BG, et al. Increased risk of ischaemic heart disease in shift workers. Lancet 1986;2 (8498):89-92.

Abstract: 504 papermill workers were followed up for 15 years and the incidence of ischaemic heart disease (IHD) in shift workers was compared with that in day workers. The relative risk (RR) of IHD rose with increasing duration of reported exposure to shift work. A significant risk of IHD was associated with an exposure of 11 - 15 years (RR = 2.2, p less than 0.04) and of 16 to 20 years (RR = 2.8, p less than 0.03. The association was independent of age and smoking history. The RR of IHD fell sharply after 20 years of shift work. This was ascribed to the pronounced positive selection that had taken place in this group
Knutsson A, Åkerstedt T, Jonsson BG. Prevalence of risk factors for coronary artery disease among day and shift workers. Scand J Work Environ Health 1988;14 (5):317-21.

Abstract: Several recent studies have indicated that shift work is associated with increased risk of coronary artery disease. In this cross-sectional study 361 shift workers were examined with respect to some major risk factors for coronary artery disease; 240 day workers constituted the reference group. A higher proportion of shift workers smoked (54 versus 39%). Shift workers also had significantly higher levels of serum triglycerides (1.61 versus 1.43 mmol/l). Body mass index and the blood pressure and total cholesterol levels did not differ between the groups. Multiple regression analyses demonstrated that shift work was significantly related to serum triglyceride levels also when age, smoking, body mass index, and other variables were controlled for. It was concluded that shift work is associated with several risk factors for coronary artery disease
Knutsson A, Hallquist J, Reuterwall C, et al. Shiftwork and myocardial infarction: a case-control study. Occup Environ Med 1999;56 (Jan.):46-50.

OBJECTIVES: Previous studies have indicated an association between shiftwork and coronary heart disease. The increased risk could be due to job strain, which could act as a mediator of disease. There is also a possibility that interaction between shiftwork and job strain could occur that may induce or modify the development of disease. We conducted this study to explore the relation between shiftwork, job strain, and myocardial infarction. METHODS: 2006 cases with acute first time myocardial infarction were compared with 2642 controls without symptoms of myocardial infarction, and obtained from the same population that gave rise to the cases (population based case-control study). RESULTS: Myocardial infarction risk was associated with shiftwork both in men (odds ratio (OR) 1.3, 95% confidence interval (95% CI) 1.1 to 1.6) and women (OR 1.3, 95% CI 0.9 to 1.8). In the age group 45-55, the relative risk was 1.6 in men and 3.0 in women. The results cannot be explained by job strain, age, job education level, or smoking. No interaction was found between shiftwork and job strain. CONCLUSIONS: The findings indicate that shiftwork is associated with myocardial infarction in both men and women. The mechanism is unclear, but the relation cannot be explained by job strain, smoking, or job education level
McNamee R, Binks K, Jones S, et al. Shiftwork and mortality from ischaemic heart disease. Occup Environ Med 1996;53:367-73.

OBJECTIVES: To investigate the relation between shift work and death from ischaemic heart disease (IHD).
METHODS: A nested case-control approach was used. The cohort comprised male manual workers who joined an industrial company aged 50 years or under between 1 January 1950 and 31 December 1992 and worked there for at least one month. Cases were 467 cohort members who died during the same period aged 75 years or under, with ischaemic heart disease (IHD) (international classification of diseases (ICD) 410-414) coded from the death certificate. For each case a control worker was chosen, who joined the company at the same age and in the same period but who survived the case. Work status (shift work or day work) was assigned to cases for their entire employment and to controls for that part of their employment which preceded the matching case's death. The main source of information was historical personnel records containing pay codes which differed for day work and shift work. Information on weight, height, blood pressure, and smoking from a pre-employment medical was available.
RESULTS: Two thirds of subjects had been employed for at least one month as shift workers and there was evidence that they had slightly better health at recruitment than day workers. The odds ratio for shift workers during the period starting 10 years after shift work began, and after adjustment for height, body mass index, blood pressure, smoking, duration of employment, and job status (skilled or unskilled) was 0.90 (90% confidence interval (90% CI): 0.68-1.21). There was no relation between risk of IHD death, and duration of shift work, but there was evidence of a reduced risk when actively employed as a shift worker, together with an increased risk in the first five years after leaving shift work to do day work.
CONCLUSIONS: Shift work did not increase the risk of death from ischaemic heart disease in this study. Those workers with poorer cardiovascular health may be under represented in groups with longer shift work experience because of health related selection out of shift work.
Notes: Case control. Reduced risk in active shiftworkers. Increased risk in ex-shiftworkers first 5 y.
Nakamura K, Shimai S, Kikuchi S, et al. Shift work and risk factors for coronary heart disease in Japanese blue-collar workers: Serum lipids and anthropometric characteristics. Occup Med 1997;47 (3):142-6.

Abstract: This study was conducted to determine if there is an association between shift work and risk factors for coronary heart disease (CHD) in Japanese male blue-collar shift workers. Health check-up data on serum lipid concentration and anthropometric indices of 33 three-shift workers and 27 two-shift workers were compared with those of day workers. The average years in age of the shift workers and day workers were 34.5 (SD = 7.1) and 32.7 (SD = 7.6) respectively. Serum total cholesterol levels of three-shift, two-shift and day workers were 5.70 (SD = 1.19) mmol/l, 4.81 (SD = 1.01) mmol/l, 4.98 (SD = 0.95) mmol/l, respectively, and the cholesterol levels of three shift workers were significantly higher than the other workers (p < 0.05). In addition, the abdominal to hip circumference ratios were 0.905 (SD = 0.060) for three-shift workers and 0.877 (SD = 0.054) for day workers, with a significant difference (p < 0.05). In the present Japanese population, three-shift workers had higher risks of CHD than day workers, which was characterized by higher levels of serum total cholesterol and tendency to central obesity. These findings held when lifestyle factors were taken into account.
Nyström L, Kolmodin-Hedman B, Jönsson E, et al. Mortality from circulatory diseases, especially ischaemic heart disease in sea pilots and boatmen in Sweden 1951-84: a retrospective cohort study. Br J Ind Med 1990;47:122-6.

Abstract: A cohort of 1455 sea pilots and boatmen employed after 1921 was established. Those identified and alive in 1951 (n = 1323) were linked to the Swedish cause of death register 1951-84. In 21 352 person-years 383 deaths were observed among sea pilots compared with 379.3 expected (SMR = 101;95% CI between 99 and 112) and in 12,127 person-years the observed number of deaths among boatmen was 136, expected 135.9 (SMR = 100) when Swedish men were used as a reference population. For ischaemic heart disease (IHD) (ICD-8: 410-414) the SMR was equal to 96 (obs = 131, exp = 137.2) for sea pilots and 91 (obs = 44, exp = 48.4) for boatmen. No trend over time or geographical differences could be observed. A healthy worker effect could not explain why there was no excess mortality from IHD.
Steenland K, Fine L. Shift work, shift change, and risk of death from heart disease at work. Am J Ind Med 1996;29:278-81.

Abstract: Some studies suggest workers who rotate shift are at increased risk of cardiovascular disease, but no studies have studied the effect of shift for workers who do not rotate. To determine wheather current shift or recent change i shift was a risk factor for ischaemic heart disease, we conducted a nested case-control study of heart disease death at work within a cohort of 21,000 men working at four heavy equipment plants. We identified 163 men who died of ischemic heart disease at work or within 1 week of working, and compared them to 781 controls who were working at the same age but did not die. Plant personelle record were used to determine duration of time on curent shift. At the time of case death, 72% of study objects were working on first shift, 22% on second, and 6% on third. The average time on shift without shift change was 9 years. There was little evidence of any difference in heart disease risk by current shift. There was some indication that recent change from afternoon or night shift to day shift had a protective effect initially, which decreased over time. ....
Tenkanen L, Sjöblom T, Kalimo R, et al. Shift work, occupation and coronary heart disease over 6-years of follow-up in the Helsinki Heart Study. Scand J Work Environ Health 1997;23 (4):257-65.

Objectives: The risk of coronary heart disease (CHD) in shift work and the possible pathways for CHD in industrial workers were studied along with the importance of shift work as an occupational class gradient of CHD risk.
Methods: Data from psychosocial questionnaire and on lifestyle factors, blood pressure, and serum lipid levels were used to follow a cohort of 1806 workers. CHD was determined from official Finnish registers. Cox's proportional hazards models were used with different covariates to evaluate the relative risks associated with shift work.
Results: All the blue-collar workers smoked more and had a higher systolic blood pressure that the white-collar workers. Three-shift workers scored low for job-decision latitude on the Karasek job stress scales. There were no difference in the total cholesterol or high density lipoprotein-cholesterol. when all the shift workers were compared with all the day workers, the relative risk of CHD was 1.5 [95% confidence intervals 1.1-2.1] when only age was adjusted for. The bue-collar workers and 2-shift and 3-shift workers had relative risk of 1.3 (0.8-2.0), 1.9 (1.1-3.4), and 1.7 (1.1-2.7), repectively, when compared with the white-collar day workers.
Conclusions: Shiftwork was an important part of the occupational gradient in CHD risk among industrial workers which could explain part of the increased CHD risk.
Tenkanen L, Sjöblom T, Härmä M. Joint effect of shift work and adverse life-style factors on the risk of coronary heart disease. Scand J Work Environ Health 1998;24 (5):351-7.

OBJECTIVES: The joint effect of shift work and certain adverse life-style factors on coronary heart disease (CHD) was studied. METHODS: Base-line measurements were obtained for a 6-year follow-up of an industrially employed cohort (N= 1806), whose shiftwork status was recorded from a questionnaire filled out by a sample of the cohort. The CHD end points (codes 410-414 of the 9th revision of the International Classification of Diseases) were obtained from official Finnish registers. In order that the joint effects of shift work and life-style factors on the risk of CHD could be studied, dichotomized variables and their combinations as a dummy variable system in Cox's proportional hazards models were used. RESULTS: The relative risks were 1, 1.6[95% confidence interval (95% CI) 1.1-2.5], 1.3(95% CI 0.9-2.1), and 2.7(95% CI 1.8-4.1) for the following combinations of shift work (SW) and smoking (SM): SW-&SM-, SW-&SM+, SW+&SM-, and SW+&SM+, respectively; and the corresponding figures for shift work and obesity (BMI > or =28 kg/m2) were 1, 1.2(95% CI0.8-1.9), 1.3(95% CI0.9-1.9), and 2.3(95% CI1.5-3.6), respectively. In both cases the effect was at least multiplicative. For the shift workers the relative risk for CHD rose gradually with increasing numbers of adverse life-style factors, but for the day workers there was no clear dose-response pattern. CONCLUSIONS: Shift work seems to trigger the effect of other, lifestyle-related risk factors of CHD and therefore calls for active prevention among shift workers
Tüchsen F. Working hours and ischaemic heart diseases in Danish men. A 4-year cohort study of hospitalization. Int J Epidemiol 1993;22 (2):215-21.

Abstract: Four groups of men with non-daytime work were identified in two surveys. The relative risk of being admitted to hospital due to ischaemic heart disease (IHD) (ICD-8, 410-414) was measured in a 4-year cohort study of all 1,293,888 economically active men in Denmark, aged 20-59 years. Compared with occupational groups having day-work only, men in occupations with frequent night and early morning work had an excess standardized hospitalization ratio (SHR) of 193, occupational groups with late evening work had an excess SHR of 216, groups working in rosters covering 24-hour services had an excess SHR of 174, and groups having other irregular working hours had an excess SHR of 172. We conclude that night work rather than shifts is responsible for a raised risk of IHD. More research is needed to develop preventive strategies.
Tüchsen F, Hannerz H, Burr H. A 12 year prospective study of circulatory disease among Danish shift workers. Occup Environ Med 2006;63 (7):451-5 Published Online First: 30 May 2006 doi: 10.1136/oem 2005.026716.

BACKGROUND: Previous studies of the risk of heart disease after shift work reached different estimates and review authors disagree about the validity of some of the studies. A cross sectional study showed that shift workers had a higher prevalence of nearly every unfavourable work environment factor investigated. Conflicts at work and low decision latitude were more frequent among shift workers, and all-day walking or standing work and part-time jobs were more often found among female shift workers. OBJECTIVES: To estimate the risk of circulatory disease in a prospective follow up of a representative sample of gainfully employed Danes, considering known or suspected confounding factors. METHODS: A cohort of 5517 people who were gainfully employed in 1990 were followed up for all hospital treatments due to circulatory diseases (390-458, ICD-8; I00-I99, ICD-10) from 1991 to 2002 inclusive. A log linear Poisson regression model was applied to control confounding factors and calculate the relative risk for 927 men and women working nights, evenings, or other non-day shifts compared to 4579 day workers. RESULTS: Non-day workers compared to day workers had a relative risk (RR) for all circulatory diseases of 1.31 (95% CI 1.06-1.63). Without control for BMI and smoking, the RR estimate was 1.33 (95% CI 1.07-1.65). For a subgroup of workers with at least three years' seniority, the RR was 1.40 (95% CI 1.09-1.81). The population based aetiological fraction of shift work was estimated to 5%. CONCLUSION: This study adds to a growing body of evidence suggesting that shift work carries an excess risk of circulatory diseases.
Virtanen SV, Notkola V. Socioeconomic inequalities in cardiovascular mortality and the role of work: a register study of Finnish men. Int J Epidemiol 2002;31 (3):614-21.

BACKGROUND: In Finland, socioeconomic inequalities in mortality have been well documented. However, the role of working conditions in the emergence of those inequalities has not been thoroughly examined. METHODS: Data came from the Longitudinal Census file, which included censuses since 1970 (every 5 years). The cohort consisted of men who were in the same occupation in 1975 and 1980, and who were between 25 and 64 years old in 1980. Farm work, mining and military occupations were excluded. Cardiovascular mortality of this cohort was followed up 1981-1994 (5.4 million person-years). Information on marital status, education and income was updated in 1985 and 1990. Working conditions were evaluated at occupational level (job exposure matrix). Poisson regression analyses were conducted to estimate the impact of independent variables on mortality. Inequalities were assessed in relation to occupational class and occupational category. RESULTS: According to the models, elimination of unfavourable working conditions would have reduced the number of all cardiovascular deaths by 8%, myocardial infarctions by 10%, and cerebrovascular deaths by 18%. The most influential job exposures appeared to be high workload, low control, noise, and shift work. Income had a strong effect on mortality. CONCLUSIONS: Working conditions explained a relatively small portion of socioeconomic inequalities in mortality. Inequalities associated with occupational category and class were more attributable to varying levels of education and income
Åkerstedt T, Alfredsson L, Theorell T. Arbetstid och sjukdom - en studie med aggregerade data. Stockholm: National Institute for Psychosocial Factors and Health 1987:1-23.

Stressforskningsrapporter Nr 190; ISSN 0280-2783

Virkkunen H, Härmä M, Kauppinen T, Tenkanen L. Shift work, occupational noise and physical workload with ensuing development of blood pressure and their joint effect on the risk of coronary heart disease. Scand J Work Environ Health 2008. Online First 17. January.
Andre oversigtsartikler
Frost P, Kolstad HA, Bonde JP. Shift work and the risk of ischaemic heart disease - a systematic review. Scandinavian Journal of Work, Environment and Health 2009;Published online 22 April 2009.

Opdateret 2. marts 2008 og 24. maj 2009.