Enderlein, G.

Enderlein, G.

Address: Risk Assessment, Federal Institute for Occupational Safety and Health, Nöldnerstrasse 40/42, 10317 Berlin

Country: Germany

Phone: 49 30 515 481 30

Fax: 49 30 515 481 70

Education: MD, 1957, University of Leipzig; Dr rer nat, 1970

Areas of interest: Epidemiological methods; occupational epidemiology; biostatistics

Tuesday, 15 February 2011 20:54

Rehabilitation and Prevention Programmes

Most individuals with recognized CVD are able to work effectively and productively in most of the jobs found in the modern workplace. Just a few decades ago, individuals surviving an acute myocardial infarction were cosseted and pampered for weeks and months with close supervision and enforced inactivity. Laboratory confirmation of the diagnosis was enough to justify labelling the individual as “permanently and totally disabled”. New diagnostic technology that provides more accurate evaluation of cardiac status and the favourable experiences of those who could not or would not accept such a label, soon demonstrated that an early return to work and an optimal level of activity was not only possible but desirable (Edwards, McCallum and Taylor 1988; Theorell et al. 1991; Theorell 1993). Today, patients commence supervised physical activity as soon as the acute effects of the infarction subside, are often out of the hospital in a few days instead of the mandatory 6 to 8 weeks of yore, and are often back on the job within a few weeks. When desirable and feasible, surgical procedures such as angioplasty, by-pass operations and even cardiac transplantation can improve the coronary blood flow, while a regimen featuring diet, exercise and control of the risk factors for CHD can minimize (or even reverse) the progression of coronary atherosclerosis.

Once the acute, often life-threatening phases of the CVD have been overcome, passive movement followed by active exercise should be initiated early during the stay in the hospital or clinic. With heart attacks, this phase is completed when the individual can climb stairs without great difficulty. At the same time, the individual is schooled in a risk-prevention regimen that includes proper diet, cardiovascular conditioning exercises, adequate rest and relaxation, and stress management. During these phases of rehabilitation, support from family members, friends and co-workers can be particularly helpful (Brusis and Weber-Falkensammer 1986). The programme can be carried out in rehabilitation facilities or in ambulatory “heart groups” under the supervision of a trained physician (Halhubar and Traencker 1986). The focus on controlling lifestyle and behavioural risk factors and controlling stress has been shown to result in a measurable reduction in the risk of re-infarction and other cardiovascular problems.

Throughout the programme the attending physician should maintain contact with the employer (and particularly with the company doctor, if there is one) to discuss the prospects for recovery and the probable duration of the period of disability, and to explore the feasibility of any special arrangements that may be needed to permit an early return to the job. The worker’s knowledge that the job is waiting and that he or she is expected to be able to return to it is a potent motivating factor for the enhancement of recovery. Experience has amply demonstrated that the success of the rehabilitation effort diminishes as the absence from work lengthens.

In instances where desirable adjustments in the job and/or the workplace are not possible or feasible, retraining and appropriate job placement can obviate unnecessary invalidism. Specially protected workshops are often helpful in reintegrating into the workplace people who have been absent from the job for long periods while receiving treatment for the serious effects of stroke, congestive heart failure or disabling angina pectoris.

Following the return to work, continued surveillance by both the attending physician and the occupational physician is eminently desirable. Periodic medical evaluations, at intervals that are frequent initially but lengthen as recovery is assured, are helpful in assessing the worker’s cardiovascular status, adjusting medications and other elements in the maintenance regimen and monitoring the adherence to the lifestyle and behavioural recommendations. Satisfactory findings in these examinations may allow the gradual easing of any work limitations or restrictions until the worker is fully integrated into the workplace.

Workplace Health Promotion and Prevention Programmes

The prevention of occupational diseases and injuries is a prime responsibility of the organization’s occupational health and safety programme. This includes primary prevention (i.e., the identifica- tion and elimination or control of potential hazards and strains by changing the work environment or the job). It is supplemented by secondary prevention measures which protect the workers from the effects of existing hazards and strains that cannot be elim- inated (i.e., personal protective equipment and periodic medical surveillance examinations). Workplace health promotion and pre- vention (HPP) programmes go beyond these goals. They place their emphasis on health-conscious behaviour as it relates to life- style, behavioural risk factors, eliminating or coping with stress and so on. They are of great significance, particularly in pre- venting CVD. The goals of HPP, as formulated by the WHO Committee on Environmental and Health Monitoring in Occupational Health, extend beyond the mere absence of disease and injury to include well-being and functional capacity (WHO 1973).

The design and operation of HPP programmes are discussed in more detail elsewhere in the chapter. In most countries, they have a particular focus on the prevention of CVDs. For example, in Germany, the “Have a heart for your heart” programme supplements the heart health circles organized by the health insurance companies (Murza and Laaser 1990, 1992), while the “Take Heart” movement in Britain and Australia has similar goals (Glasgow et al. 1995).

That such programmes are effective was verified in the 1980s by the WHO Collaborative Trial in Prevention of Heart Disease, which was carried out in 40 pairs of factories in four European countries and involved approximately 61,000 men aged 40 to 59. The preventive measures largely comprised health education activities, carried out primarily by the organization’s employee health service, focused on cholesterol-lowering diets, giving up cigarette smoking, weight control, increased physical activity and controlling hypertension. A randomized screening of 10% of the eligible workers in the factories designated as controls demonstrated that during the 4 to 7 years of the study, overall risk of CVDs could be reduced by 11.1% (19.4% among those initially at high risk). In the study factories, mortality from CHDs fell by 7.4%, while overall mortality fell by 2.7%. The best results were achieved in Belgium, where the intervention was carried out continuously during the entire study period, while the poorest results were seen in Britain, where the prevention activities were sharply curtailed prior to the last follow-up examination. This disparity emphasizes the relationship of success to the duration of the health education effort; it takes time to inculcate the desired lifestyle changes. The intensity of the educational effort was also a factor: in Italy, where six full-time health educators were involved, a 28% reduction in overall risk-factor profile was achieved, whereas in Britain, where only two full-time educators served three times the number of workers, a risk factor reduction of only 4% was achieved.

While the time required to detect reductions in CHD mortality and morbidity is a formidable limiting factor in epidemiological studies aimed at evaluating the results of company health programmes (Mannebach 1989), reductions in risk factors have been demonstrated (Janssen 1991; Gomel et al. 1993; Glasgow et al. 1995). Temporary decreases in the number of lost workdays and a decline in hospitalization rates have been reported (Harris 1994). There seems to be general agreement that HPP activities in the community and particularly in the workplace have significantly contributed to the reduction in cardiovascular mortality in the United States and other western industrialized countries.

Conclusion

CVDs loom large in the workplace, not so much because the cardiovascular system is particularly vulnerable to environmental and job hazards, but because they are so common in the popu- lation of working age. The workplace offers a singularly advant- ageous arena for the detection of unrecognized, asymptomatic CVDs, for the circumvention of workplace factors that might accelerate or aggravate them and for the identification of factors that increase the risk of CVDs and the mounting of programmes to eliminate or control them. When CVDs do occur, prompt attention to control of job-related circumstances that may prolong or increase their severity can minimize the extent and duration of disability, while early, professionally supervised rehabilitation efforts will facilitate the restoration of working capacity and reduce the risk of recurrences.

Physical, Chemcial and Biological Hazards

The intact cardiovascular system is remarkably resistant to the harmful effects of physical, chemical and biological hazards encountered on the job or in the workplace. With a very few exceptions, such hazards are rarely a direct cause of CVDs. On the other hand, once the integrity of the cardiovascular system is compromised—and this may be entirely silent and unrecognized—exposure to these hazards may contribute to the ongoing development of a disease process or precipitate symptoms reflecting functional impairment. This dictates early identification of workers with incipient CVD and modification of their jobs and/or the work environment to reduce the risk of harmful effects. The following segments will include brief discussions of some of the more commonly encountered occupational hazards that may affect the cardiovascular system. Each of the hazards presented below is discussed more fully elsewhere in the Encyclopaedia.

 

 

Back

Risk factors are genetic, physiological, behavioural and socioeconomic characteristics of individuals that place them in a cohort of the population that is more likely to develop a particular health problem or disease than the rest of the population. Usually applied to multifactorial diseases for which there is no single precise cause, they have been particularly useful in identifying candidates for primary preventive measures and in assessing the effectiveness of the prevention programme in controlling the risk factors being targeted. They owe their development to large-scale prospective population studies, such as the Framingham study of coronary artery disease and stroke conducted in Framingham, Massachusetts, in the United States, other epidemiological studies, intervention studies and experimental research.

It should be emphasized that risk factors are merely expressions of probability—that is, they are not absolute nor are they diagnostic. Having one or more risk factors for a particular disease does not necessarily mean that an individual will develop the disease, nor does it mean that an individual without any risk factors will escape the disease. Risk factors are individual characteristics which affect that person’s chances of developing a particular disease or group of diseases within a defined future time period. Categories of risk factors include:

  • somatic factors, such as high blood pressure, lipid metabolism disorders, overweight and diabetes mellitus
  • behavioural factors, such as smoking, poor nutrition, lack of physical movement, type-A personality, high alcohol consumption and drug abuse
  • strains, including exposures in the occupational, social and private spheres.

 

Naturally, genetic and dispositional factors also play a role in high blood pressure, diabetes mellitus and lipid metabolism disorders. Many of the risk factors promote the development of arteriosclerosis, which is a significant precondition for the onset of coronary heart disease.

Some risk factors may put the individual at risk for the development of more than one disease; for example, cigarette smoking is associated with coronary artery disease, stroke and lung cancer. At the same time, an individual may have multiple risk factors for a particular disease; these may be additive but, more often, the combinations of risk factors may be multiplicative. Somatic and lifestyle factors have been identified as the main risk factors for coronary heart disease and stroke.

Hypertension

Hypertension (increased blood pressure), a disease in its own right, is one of the major risk factors for coronary heart disease (CHD) and stroke. As defined by the WHO, blood pressure is normal when the diastolic is below 90 mm Hg and the systolic is below 140 mm Hg. In threshold or borderline hypertension, the diastolic ranges from 90 to 94 mm Hg and the systolic from 140 to 159 mm Hg. Individuals with diastolic pressures equal to or greater than 95 mm Hg and systolic pressures equal to or greater than 160 mm Hg are designated as being hypertensive. Studies have shown, however, that such sharp criteria are not entirely correct. Some individuals have a “labile” blood pressure—the pressure fluctuates between normal and hypertensive levels depending on the circumstances of the moment. Further, without regard to the specific categories, there is a linear progression of relative risk as the pressure rises above the normal level.

In the United States, for example, the incidence rate of CHD and stroke among men aged 55 to 61 was 1.61% per year for those whose blood pressure was normal compared to 4.6% per year for those with hypertension (National Heart, Lung and Blood Institute 1981).

Diastolic pressures over 94 mm Hg were found in 2 to 36% of the population aged 35 to 64 years, according to the WHO-MONICA study. In many countries of Central, Northern and Eastern Europe (e.g., Russia, the Czech Republic, Finland, Scotland, Romania, France and parts of Germany, as well as Malta), hypertension was found in over 30% of the population aged 35 to 54, while in countries including Spain, Denmark, Belgium, Luxembourg, Canada and the United States, the corresponding figure was less than 20% (WHO-MONICA 1988). The rates tend to increase with age, and there are racial differences. (In the United States, at least, hypertension is more frequent among African-Americans than in the White population.)

Risks for developing hypertension

The important risk factors for developing hypertension are excess body weight, high salt intake, a series of other nutritional factors, high alcohol consumption, physical inactivity, and psychosocial factors, including stress (Levi 1983). Furthermore, there is a certain genetic component whose relative significance is not yet fully understood (WHO 1985). Frequent familial high blood pressure should be considered a danger and special attention paid to controlling lifestyle factors.

There is evidence that psychosocial and psychophysical factors, in conjunction with the job, can have an influence on developing hypertension, especially for short-term blood pressure increases. Increases have been found in the concentration of certain hormones (adrenalin and noradrenalin) as well as cortisol (Levi 1972), which, alone and in combination with high salt consumption, can lead to increased blood pressure. Work stress also appears to be related to hypertension. A dose-effect relationship with intensity of air traffic was shown (Levi 1972; WHO 1985) in comparing groups of air traffic controllers with different high psychic strain.

Treatment of hypertension

Hypertension can and should be treated, even in the absence of any symptoms. Lifestyle changes such as weight control, reduction of sodium intake and regular physical exercise, coupled when necessary with anti-hypertensive medications, regularly evoke re- ductions in blood pressure, often to normal levels. Unfortunately, many individuals found to be hypertensive are not receiving adequate treatment. According to the WHO-MONICA study (1988), less than 20% of hypertensive women in Russia, Malta, eastern Germany, Scotland, Finland and Italy were receiving adequate treatment during the mid-1980s, while the comparable figure for men in Ireland, Germany, China, Russia, Malta, Finland, Poland, France and Italy was under 15%.

Prevention of hypertension

The essence of preventing hypertension is identifying individuals with blood pressure elevation through periodic screening or medical examination programmes, repeated checks to verify the extent and duration of the elevation, and the institution of an appropriate treatment regimen that will be maintained indefinitely. Those with a family history of hypertension should have their pressures checked more frequently and should be guided to elimination or control of any risk factors they may present. Control of alcohol abuse, physical training and physical fitness, normal weight maintenance and efforts to reduce psychological stress are all important elements of prevention programmes. Improvement in workplace conditions, such as reducing noise and excess heat, are other preventive measures.

The workplace is a uniquely advantageous arena for programmes aimed at the detection, monitoring and control of hypertension in the workforce. Convenience and low or no cost make them attractive to the participants and the positive effects of peer pressure from co-workers tend to enhance their compliance and the success of the programme.

Hyperlipidemia

Many long-term international studies have demonstrated a convincing relationship between abnormalities in lipid metabolism and an increased risk of CHD and stroke. This is particularly true for elevated total cholesterol and LDL (low density lipoproteins) and/or low levels of HDL (high density lipoproteins). Recent research provides further evidence linking the excess risk with different lipoprotein fractions (WHO 1994a).

The frequency of elevated total cholesterol levels >>6.5 mmol/l) was shown to vary considerably in population groups by the worldwide WHO-MONICA studies in the mid-1980s (WHO- MONICA 1988). The rate of hypercholesterolemia for popu- lations of working age (35 to 64 years of age) ranged from 1.3 to 46.5% for men and 1.7 to 48.7% for women. Although the ranges were generally similar, the mean cholesterol levels for the study groups in different countries varied significantly: in Finland, Scot- land, East Germany, the Benelux countries and Malta, a mean of over 6 mmol/l was found, while the means were lower in east Asian countries like China (4.1 mmol/l) and Japan (5.0 mmol/l). In both regions, the means were below 6.5 mmol/l (250 mg/dl), the level designated as the threshold of normal; however, as noted above for blood pressure, there is a progressive increase of risk as the level rises, rather than a sharp demarcation between normal and abnormal. Indeed, some authorities have pegged a total chol- esterol level of 180 mg/dl as the optimal level that should not be exceeded.

It should be noted that gender is a factor, with women averaging lower levels of HDL. This may be one reason why women of working age have a lower mortality rate from CHD.

Except for the relatively few individuals with hereditary hyper- cholesterolemia, cholesterol levels generally reflect the dietary intake of foods rich in cholesterol and saturated fats. Diets based on fruit, plant products and fish, with reduced total fat intake and substitution of poly-unsaturated fats, are generally associated with low cholesterol levels. Although their role is not yet entirely clear, intake of anti-oxidants (vitamin E, carotene, selenium and so on) is also thought to influence cholesterol levels.

Factors associated with higher levels of HDL cholesterol, the “protective” form of lipoprotein, include race (Black), gender (female), normal weight, physical exercise and moderate alcohol intake.

Socio-economic level also appears to play a role, at least in industrialized countries, as in West Germany, where higher cholesterol levels were found in population groups of both men and women with lower education levels (under ten years of schooling) compared to those completing 12 years of education (Heinemann 1993).

Cigarette Smoking

Cigarette smoking is among the most important risk factors for CVD. The risk from cigarette smoking is directly related to the number of cigarettes one smokes, the length of time one has been smoking, the age at which one began to smoke, the amount one inhales and the tar, nicotine and carbon monoxide content of the inspired smoke. Figure 1 illustrates the striking increase in CHD mortality among cigarette smokers compared to non-smokers. This increased risk is demonstrated among both men and women and in all socio-economic classes.

The relative risk of cigarette smoking declines after tobacco use is discontinued. This is progressive; after about ten years of non-smoking, the risk is down almost to the level of those who never smoked.

Recent evidence has demonstrated that those inhaling “second-hand smoke” (i.e., passive inhalation of smoke from cigarettes smoked by others) are also at significant risk (Wells 1994; Glantz and Parmley 1995).

Rates of cigarette smoking vary among countries, as demonstrated by the international WHO-MONICA study (1988). The highest rates for men aged 35 to 64 were found in Russia, Poland, Scotland, Hungary, Italy, Malta, Japan and China. More women smokers were found in Scotland, Denmark, Ireland, the United States, Hungary and Poland (the recent Polish data are limited to large cities).

Social status and occupational level are factors in the level of smoking among workers. Figure 1, for example, demonstrates that the proportions of smokers among men in East Germany increased in the lower social classes. The reverse is found in countries with relatively low numbers of smokers, where there is more smoking among those at higher social levels. In East Germany, smoking is also more frequent among shift-workers when compared with those on a “normal” work schedule.

Figure 1. Relative mortality risk from cardiovascular diseases for smokers (including ex-smokers) and social classes compared to non-smoking, normal weight, skilled workers (male) based on occupational medical care examinations in East Germany, mortality 1985-89, N= 2.7 million person years.

CAR010F1

Unbalanced Nutrition, Salt Consumption

In most industrialized countries traditional low-fat nutrition has been replaced by high-calorie, high-fat, low carbohydrate, too sweet or too salty eating habits. This contributes to the development of overweight, high blood pressure, and high cholesterol level as elements of high cardiovascular risk. The heavy consumption of animal fats, with their high proportion of saturated fatty acids, leads to an increase in LDL cholesterol and increased risk. Fats derived from vegetables are much lower in these substances (WHO 1994a). Eating habits are also strongly associated with both socio-economic level and occupation.

Overweight

Overweight (excess fat or obesity rather than increased muscle mass) is a cardiovascular risk factor of lesser direct significance. There is evidence that the male pattern of excess fat distribution (abdominal obesity) is associated with a greater risk of cardiovascular and metabolic problems than the female (pelvic) type of fat distribution.

Overweight is associated with hypertension, hypercholesterolemia and diabetes mellitus, and, to a much greater extent in women than men, tends to increase with age (Heuchert and Enderlein 1994) (Figure 2). It is also a risk factor for musculoskeletal problems and osteoarthritis, and makes physical exercise more difficult. The frequency of significant overweight varies considerably among countries. Random population surveys conducted by the WHO-MONICA project found it in more than 20% of females aged 35 to 64 in the Czech Republic, East Germany, Finland, France, Hungary, Poland, Russia, Spain and Yugoslavia, and in both sexes in Lithuania, Malta and Romania. In China, Japan, New Zealand and Sweden, fewer than 10% of both men and women in this age group were significantly overweight.

Common causes of overweight include familial factors (these may in part be genetic but more often reflect common dietary habits), overeating, high-fat and high-carbohydrate diets and lack of physical exercise. Overweight tends to be more common among the lower socio-economic strata, particularly among women, where, among other factors, financial constraints limit the availability of a more balanced diet. Population studies in Germany demonstrated that the proportion of significant overweight among those with lower education levels is 3 to 5 times greater than that among people with more education, and that some occupations, notably food preparation, agriculture and to some extent shift work, have a high percentage of overweight people (Figure 3) (Heinemann 1993).

Figure 2. Prevalence of hypertension by age, sex and six levels of relative body weight according tot he body-mass index (BMI) in occupational medical care examinations in East Germany (normal BMI values are underlined).

CAR010F2

Figure 3. Relative risk from overweight by length of education(years of schooling) in Germay (population 25-64 years).

 CAR010F3

Physical Inactivity

The close association of hypertension, overweight and diabetes mellitus with lack of exercise at work and/or off the job has made physical inactivity a significant risk factor for CHD and stroke (Briazgounov 1988; WHO 1994a). A number of studies have demonstrated that, holding all other risk factors constant, there was a lower mortality rate among persons engaging regularly in high-intensity exercises than among those with a sedentary lifestyle.

The amount of exercise is readily measured by noting its duration and either the amount of physical work accomplished or the extent of the exercise-induced increase in heart rate and the time required for that rate to return to its resting level. The latter is also useful as an indicator of the level of cardiovascular fitness: with regular physical training, there will be less of an increase in heart rate and a more rapid return to the resting rate for a given intensity of exercise.

Workplace physical fitness programmes have been shown to be effective in enhancing cardiovascular fitness. Participants in these tend also to give up cigarette smoking and to pay greater attention to proper diets, thus significantly reducing their risk of CHD and stroke.

Alcohol

High alcohol consumption, especially the drinking of high-proof spirits, has been associated with a greater risk of hypertension, stroke and myocardiopathy, while moderate alcohol use, particularly of wine, has been found to reduce the risk of CHD (WHO 1994a). This has been associated with the lower CHD mortality among the upper social strata in industrialized countries, who generally prefer wine to “hard” liquors. It should also be noted that while their alcohol intake may be similar to that of wine drinkers, beer drinkers tend to accumulate excess weight, which, as noted above, may increase their risk.

Socio-economic Factors

A strong correlation between socio-economic status and the risk of CVD has been demonstrated by analyses of the death register mortality studies in Britain, Scandinavia, Western Europe, the United States and Japan. For example, in eastern Germany, the cardiovascular death rate is considerably lower for the upper social classes than for the lower classes (see Figure 1) (Marmot and Theorell 1991). In England and Wales, where general mortality rates are declining, the relative gap between the upper and lower classes is widening.

Socio-economic status is typically defined by such indicators as occupation, occupational qualifications and position, level of education and, in some instances, income level. These are readily translated into standard of living, nutritional patterns, free-time activities, family size and access to medical care. As noted above, behavioural risk factors (such as smoking and diet) and the somatic risk factors (such as overweight, hypertension and hyperlipidemia) vary considerably among social classes and occupational groups (Mielck 1994; Helmert, Shea and Maschewsky Schneider 1995).

Occupational Psychosocial Factors and Stress

Occupational stress

Psychosocial factors at the workplace primarily refer to the combined effect of working environment, work content, work demands and technological-organizational conditions, and also to personal factors like capability, psychological sensitivity, and finally also to health indicators (Karasek and Theorell 1990; Siegrist 1995).

The role of acute stress on people who already suffer from cardiovascular disease is uncontested. Stress leads to episodes of angina pectoris, rhythm disorders and heart failure; it can also precipitate a stroke and/or a heart attack. In this context stress is generally understood to mean acute physical stress. But evidence has been mounting that acute psychosocial stress can also have these effects. Studies from the 1950s showed that people who work two jobs at a time, or who work overtime for long periods, have a relatively higher risk of heart attack, even at a young age. Other studies showed that in the same job, the person with the greater work and time pressure and frequent problems on the job is at significantly greater risk (Mielck 1994).

In the last 15 years, job stress research suggests a causal relationship between work stress and the incidence of cardiovascular disease. This is true for cardiovascular mortality as well as frequency of coronary disease and hypertension (Schnall, Landsbergis and Baker 1994). Karasek’s job strain model defined two factors that could lead to an increased incidence of cardiovascular disease:

  • extent of job demands
  • extent of decision-making latitude.

 

Later Johnson added as a third factor the extent of social support (Kristensen 1995) which is discussed more fully elsewhere in this Encyclopaedia. The chapter Psychosocial and Organizational Factors includes discussions on individual factors, such as Type A personality, as well as social support and other mechan- isms for overcoming the effects of stress.

The effects of factors, whether individual or situational, that lead to increased risk of cardiovascular disease can be reduced by “coping mechanisms”, that is, by recognizing the problem and overcoming it by attempting to make the best of the situation.

Until now, measures aimed at the individual have predominated in the prevention of the negative health effects of work stress. Increasingly, improvements in organizing the work and expanding employee decision-making latitude have been used (e.g., action research and collective bargaining; in Germany, occupational quality and health circles) to achieve an improvement in productivity as well as to humanize the work by decreasing the stress load (Landsbergis et al. 1993).

Night and Shift Work

Numerous publications in the international literature cover the health risks posed by night and shift work. It is generally accepted that shift work is one risk factor which, together with other relev- ant (including indirect) work-related demands and expectation factors, leads to adverse effects.

In the last decade research on shift work has increasingly dealt with the long-term effects of night and shift work on the frequency of cardiovascular disease, especially ischaemic heart disease and myocardial infarction, as well as cardiovascular risk factors. The results of epidemiological studies, especially from Scandinavia, permit a higher risk of ischemic heart disease and myocardial infarction to be presumed for shift workers (Alfredsson, Karasek and Theorell 1982; Alfredsson, Spetz and Theorell 1985; Knutsson et al. 1986; Tüchsen 1993). In Denmark it was even estimated that 7% of cardiovascular disease in men as well as women can be traced to shift work (Olsen and Kristensen 1991).

The hypothesis that night and shift workers have a higher risk (estimated relative risk approximately 1.4) for cardiovascular disease is supported by other studies that consider cardiovascular risk factors like hypertension or fatty acid levels for shift workers as compared to day workers. Various studies have shown that night and shift work may induce increased blood pressure and hypertension as well as increased triglyceride and/or serum cholesterol (as well as normal range fluctuations for HDL-cholesterol in increased total cholesterol). These changes, together with other risk factors (like heavy cigarette smoking and overweight among shift workers), can cause increased morbidity and mortality due to atherosclerotic disease (DeBacker et al. 1984; DeBacker et al. 1987; Härenstam et al. 1987; Knutsson 1989; Lavie et al. 1989; Lennernäs, Åkerstedt and Hambraeus 1994; Orth-Gomer 1983; Romon et al. 1992).

In all, the question of possible causal links between shift work and atherosclerosis cannot be definitively answered at present, as the pathomechanism is not sufficiently clear. Possible mechanisms discussed in the literature include changes in nutrition and smoking habits, poor sleep quality, increases in lipid level, chronic stress from social and psychological demands and disrupted circadian rhythms. Knutsson (1989) has proposed an interesting pathogenesis for the long-term effects of shift work on chronic morbidity.

The effects of various associated attributes on risk estimation have hardly been studied, since in the occupational field other stress-inducing working conditions (noise, chemical hazardous materials, psychosocial stress, monotony and so on) are connected with shift work. From the observation that unhealthy nutritional and smoking habits are often connected with shift work, it is often concluded that an increased risk of cardiovascular disease among shift workers is more the indirect result of unhealthy behaviour (smoking, poor nutrition and so on) than directly the result of night or shift work (Rutenfranz, Knauth and Angersbach 1981). Furthermore, the obvious hypothesis of whether shift work promotes this conduct or whether the difference comes primarily from the choice of workplace and occupation must be tested. But regardless of the unanswered questions, special attention must be paid in cardiovascular prevention programmes to night and shift workers as a risk group.

Summary

In summary, risk factors represent a broad variety of genetic, somatic, physiological, behavioural and psychosocial characteristics which can be assessed individually for individuals and for groups of individuals. In the aggregate, they reflect the probability that CVD, or more precisely in the context of this article, CHD or stroke will develop. In addition to elucidating the causes and pathogenesis of multifactorial diseases, their chief importance is that they delineate individuals who should be targets for risk factor elimination or control, an exercise admirably suited to the workplace, while repeated risk assessments over time demonstrate the success of that preventive effort.

 

Back

In the following article, the term cardiovascular diseases (CVDs) refers to organic and functional disorders of the heart and circu- latory system, including the resultant damage to other organ systems, which are classified under numbers 390 to 459 in the 9th revision of the International Classification of Diseases (ICD) (World Health Organization (WHO) 1975). Based essentially on international statistics assembled by the WHO and data collected in Germany, the article discusses the prevalence of CVDs, new disease rates, and frequency of deaths, morbidity and disability.

Definition and Prevalence in the Working-Age Population

Coronary artery disease (ICD 410-414) resulting in ischaemia of the myocardium is probably the most significant CVD in the working population, particularly in industrialized countries. This condition results from a constriction in the vascular system that supplies the heart muscle, a problem caused primarily by arteriosclerosis. It affects 0.9 to 1.5% of working-age men and 0.5 to 1.0% of women.

Inflammatory diseases (ICD 420-423) may involve the endo- cardium, the heart valves, the pericardium and/or the heart muscle (myocardium) itself. They are less common in industrialized countries, where their frequency is well below 0.01% of the adult population, but are seen more frequently in developing countries, perhaps reflecting the greater prevalence of nutritional disorders and infectious diseases.

Heart rhythm disorders (ICD 427) are relatively rare, although much media attention has been given to recent instances of disability and sudden death among prominent professional athletes. Although they can have a significant impact on the ability to work, they are often asymptomatic and transitory.

The myocardiopathies (ICD 424) are conditions which involve enlargement or thickening of the heart musculation, effectively narrowing the vessels and weakening the heart. They have attracted more attention in recent years, largely because of improved methods of diagnosis, although their pathogenesis is often obscure. They have been attributed to infections, metabolic diseases, immunologic disorders, inflammatory diseases involving the capillaries and, of particular importance in this volume, to toxic exposures in the workplace. They are divided into three types:

    • dilative—the most common form (5 to 15 cases per 100,000 people), which is associated with the functional weakening of the heart
    • hypertrophic—thickening and enlargement of the myocardium resulting in relative insufficiency of the coronary arteries
    • restrictive—a rare type in which myocardial contractions are limited.

         

        Hypertension (ICD 401-405) (increased systolic and/or diastolic blood pressure) is the most common circulatory disease, being found among 15 to 20% of working people in industrialized countries. It is discussed in greater detail below.

        Atherosclerotic changes in the major blood vessels (ICD 440), often associated with hypertension, cause disease in the organs they serve. Foremost among these is cerebrovascular disease (ICD 430-438), which may result in a stroke due to infarction and/or haemorrhage. This occurs in 0.3 to 1.0% of working people, most commonly among those aged 40 and older.

        Atherosclerotic diseases, including coronary artery disease, stroke and hypertension, by far the most common cardiovascular diseases in the working population, are multifactorial in origin and have their onset early in life. They are of importance in the workplace because:

          • so large a proportion of the workforce has an asymptomatic or unrecognized form of cardiovascular disease
          • the development of that disease may be aggravated or acute symptomatic events precipitated by working conditions and job demands
          • the acute onset of a symptomatic phase of the cardiovascular disease is often attributed to the job and/or the workplace environment
          • most individuals with an established cardiovascular disease are capable of working productively, albeit, sometimes, only after effective rehabilitation and job retraining
          • the workplace is a uniquely propitious arena for primary and secondary preventive programmes.

                   

                  Functional circulatory disorders in the extremities (ICD 443) include Raynaud’s disease, short-term pallor of the fingers, and are relatively rare. Some occupational conditions, such as frostbite, long-term exposure to vinyl chloride and hand-arm exposure to vibration can induce these disorders.

                  Varicosities in the leg veins (ICD 454), often improperly dismissed as a cosmetic problem, are frequent among women, especially during pregnancy. While a hereditary tendency to weakness of the vein walls may be a factor, they are usually associated with long periods of standing in one position without movement, during which the static pressure within the veins is increased. The result- ant discomfort and leg oedema often dictate change or modifi- cation of the job.

                  Annual incidence rates

                  Among the CVDs, hypertension has the highest annual new case rate among working people aged 35 to 64. New cases develop in approximately 1% of that population every year. Next in frequency are coronary heart disease (8 to 92 new cases of acute heart attack per 10,000 men per year, and 3 to 16 new cases per 10,000 women per year) and stroke (12 to 30 cases per 10,000 men per year, and 6 to 30 cases per 10,000 women per year). As demonstrated by global data collected by the WHO-Monica project (WHO-MONICA 1994; WHO-MONICA 1988), the lowest new incidence rates for heart attack were found among men in China and women in Spain, while the highest rates were found among both men and women in Scotland. The significance of these data is that in the population of working age, 40 to 60% of heart attack victims and 30 to 40% of stroke victims do not survive their initial episodes.

                  Mortality

                  Within the primary working ages of 15 to 64, only 8 to 18% of deaths from CVDs occur prior to age 45. Most occur after age 45, with the annual rate increasing with age. The rates, which have been changing, vary considerably from country to country (WHO 1994b).

                  Table 1 shows the death rates for men and for women aged 45 to 54 and 55 to 64 for some countries. Note that the death rates for men are consistently higher than those for women of corresponding ages. Table 2 compares the death rates for various CVDs among people aged 55 to 64 in five countries.

                  Table 1. Mortality from cardiovascular diseases in 1991 and 1990 in the age groups 45-54 and 55-64 for selected countries.

                  Country

                  Men

                  Women

                  45-54 Years

                  55-64 Years

                  45-54 Years

                  55-64 Years

                  Rate

                  %

                  Rate

                  %

                  Rate

                  %

                  Rate

                  %

                  Russia**

                  528

                  36

                  1,290

                  44

                  162

                  33

                  559

                  49

                  Poland**

                  480

                  38

                  1,193

                  45

                  134

                  31

                  430

                  42

                  Argentina*

                  317

                  40

                  847

                  44

                  131

                  33

                  339

                  39

                  Britain**

                  198

                  42

                  665

                  47

                  59

                  20

                  267

                  32

                  USA*

                  212

                  35

                  623

                  40

                  83

                  24

                  273

                  31

                  Germany**

                  181

                  29

                  597

                  38

                  55

                  18

                  213

                  30

                  Italy*

                  123

                  27

                  404

                  30

                  41

                  18

                  148

                  25

                  Mexico**

                  128

                  17

                  346

                  23

                  82

                  19

                  230

                  24

                  France**

                  102

                  17

                  311

                  22

                  30

                  12

                  94

                  18

                  Japan**

                  111

                  27

                  281

                  26

                  48

                  22

                  119

                  26

                  *1990. **1991. Rate=Deaths per 100,000 inhabitants. % is from all causes of death in the age group.

                   

                  Table 2. Mortality rates from special cardiovascular diagnosis groups in the years 1991 and 1990 in the age group 55-64 for selected countries

                  Diagnosis group
                  (ICD 9th Rev.)

                  Russia (1991)

                  USA (1990)

                  Germany (1991)

                  France (1991)

                  Japan (1991)

                   

                  M

                  F

                  M

                  F

                  M

                  F

                  M

                  F

                  M

                  F

                  393–398

                  16.8

                  21.9

                  3.3

                  4.6

                  3.6

                  4.4

                  2.2

                  2.3

                  1.2

                  1.9

                  401–405

                  22.2

                  18.5

                  23.0

                  14.6

                  16.9

                  9.7

                  9.4

                  4.4

                  4.0

                  1.6

                  410

                  160.2

                  48.9

                  216.4

                  79.9

                  245.2

                  61.3

                  100.7

                  20.5

                  45.9

                  13.7

                  411–414

                  586.3

                  189.9

                  159.0

                  59.5

                  99.2

                  31.8

                  35.8

                  6.8

                  15.2

                  4.2

                  415–429

                  60.9

                  24.0

                  140.4

                  64.7

                  112.8

                  49.2

                  73.2

                  27.0

                  98.7

                  40.9

                  430–438

                  385.0

                  228.5

                  54.4

                  42.2

                  84.1

                  43.8

                  59.1

                  26.7

                  107.3

                  53.6

                  440

                  441–448


                  {50.0}


                  {19.2}

                  4.4

                  18.4

                  2.1

                  6.7

                  11.8

                  15.5

                  3.8

                  4.2

                  1.5

                  23.4

                  0.3

                  3.8

                  0.3

                  3.8

                  0.1

                  2.6

                  Total 390–459

                  1,290

                  559

                  623

                  273

                  597

                  213

                  311

                  94

                  281

                  119

                  Deaths per 100,000 inhabitants; M=male; F=female.

                  Work Disability and Early Retirement

                  Diagnosis-related statistics on time lost from work represent an important perspective on the impact of morbidity on the working population, even though the diagnostic designations are usually less precise than in cases of early retirement because of disability. The case rates, usually expressed in cases per 10,000 employees, provide an index of the frequency of the disease categories, while the average number of days lost per case indicates the relative seriousness of particular diseases. Thus, according to statistics on 10 million workers in western Germany compiled by the Allgemeinen Ortskrankenkasse, CVDs accounted for 7.7% of the total disability in 1991-92, although the number of cases for that period was only 4.6% of the total (Table 3). In some countries, where early retirement is provided when work ability is reduced due to illness, the pattern of disability mirrors the rates for different categories of CVD.

                  Table 3. Rate of cardiovascular disease among early pensioners* due to reduced ability to work (N = 576,079) and diagnosis-related work disability in the western part of Germany, 1990-92

                  Diagnosis group
                  (ICD 9th Rev.)

                  Main cause of illness

                  Access to early retirement; number  per 100,000 early retirees

                  Average annual work disability 1990–92

                   

                  Cases per 100,000 employed

                  Duration (days) per case

                   

                  Men

                  Women

                  Men

                  Women

                  Men

                  Women

                  390–392

                  Acute rheumatic fever

                  16

                  24

                  49

                  60

                  28.1

                  32.8

                  393–398

                  Chronic rheumatic heart disease

                  604

                  605

                  24

                  20

                  67.5

                  64.5

                  401–405

                  Hypertension, high blood pressure diseases

                  4,158

                  4,709

                  982

                  1,166

                  24.5

                  21.6

                  410–414

                  Ischaemic heart diseases

                  9,635

                  2,981

                  1,176

                  529

                  51.2

                  35.4

                  410, 412

                  Acute and existing myocardial infarction

                  2,293

                  621

                  276

                  73

                  85.8

                  68.4

                  414

                  Coronary heart disease

                  6,932

                  2,183

                  337

                  135

                  50.8

                  37.4

                  415–417

                  Pulmonary circulatory diseases

                  248

                  124

                  23

                  26

                  58.5

                  44.8

                  420–429

                  Other non-rheumatic heart diseases

                  3,434

                  1,947

                  645

                  544

                  36.3

                  25.7

                  420–423

                  Inflammatory heart diseases

                  141

                  118

                  20

                  12

                  49.4

                  48.5

                  424

                  Heart valve disorders

                  108

                  119

                  22

                  18

                  45.6

                  38.5

                  425

                  Myocardiopathy

                  1,257

                  402

                  38

                  14

                  66.8

                  49.2

                  426

                  Stimulus performance disorder

                  86

                  55

                  12

                  7

                  39.6

                  45.0

                  427

                  Cardiac rhythm disorder

                  734

                  470

                  291

                  274

                  29.3

                  21.8

                  428

                  Cardiac insufficiency

                  981

                  722

                  82

                  61

                  62.4

                  42.5

                  430–438

                  Cerebrovascular diseases

                  4,415

                  2,592

                  172

                  120

                  75.6

                  58.9

                  440–448

                  Diseases of the arteries, arterioles and capillaries

                  3,785

                  1,540

                  238

                  90

                  59.9

                  44.5

                  440

                  Arteriosclerosis

                  2,453

                  1,090

                  27

                  10

                  71.7

                  47.6

                  443

                  Raynaud’s disease and other vascular diseases

                  107

                  53

                  63

                  25

                  50.6

                  33.5

                  444

                  Arterial embolism and thrombosis

                  219

                  72

                  113

                  34

                  63.3

                  49.5

                  451–456

                  Diseases of the veins

                  464

                  679

                  1,020

                  1,427

                  22.9

                  20.3

                  457

                  Noninfectious diseases of the lymph nodes

                  16

                  122

                  142

                  132

                  10.4

                  14.2

                  458

                  Hypotension

                  29

                  62

                  616

                  1,501

                  9.4

                  9.5

                  459

                  Other circulatory diseases

                  37

                  41

                  1,056

                  2,094

                  11.5

                  10.2

                  390–459

                  Total cardiovascular diseases

                  26,843

                  15,426

                  6,143

                  7,761

                  29.6

                  18.9

                  *Early pensioned: Statutory pensions insurance for former Federal Republic of Germany, work disability AOK-West.

                   

                  Back

                  " DISCLAIMER: The ILO does not take responsibility for content presented on this web portal that is presented in any language other than English, which is the language used for the initial production and peer-review of original content. Certain statistics have not been updated since the production of the 4th edition of the Encyclopaedia (1998)."

                  Contents