July 2000

( Please note for each question there is first a short answer, followed by a fairly detailed explanation.)

1. Neurocardiac mechanisms of heart disease risk among professional drivers

a) Definition of Professional Drivers and what do they all have in common?
We define professional drivers as those workers whose main job is to operate a motor vehicle in traffic conditions. This includes chauffeurs, bus, truck, tram, trolley, taxi and ambulance drivers.

While each of these groups has its own distinguishing characteristics and problems, they share common features that are critically important stressors. Namely, all professional drivers perform what we call "threat-avoidant vigilant activity" where they must maintain a high level of attention, in order to follow a large number of information sources simultaneously to which they must rapidly respond, whereby a momentary lapse or wrong decision can have serious, potentially fatal consequences. The burden is heaviest upon their visual systems, but also they must be keep their hearing and somatosensory systems on alert. This work is performed while seated in a relatively fixed position in a confined space.

b) What are some neurocardiac mechanisms?
These mechanisms describe how the brain affects the activity of the cardiovascular system. We now use the term "econeurocardiology" to represent the complex processes by which social factors, such as work stressors, are perceived and processed by the central nervous system, resulting in pathophysiologic changes that increase risk of cardiovascular disease.

Fight or flight and vigilance responses

What we have described above is the starting point for understanding the load carried by the brain and transmitted to the cardiovascular system in response to the traffic environment. Let's first look at the natural environment, where a threat is perceived by the brain and, via the autonomic nervous system and neuroendocrine mechanisms, activates the heart and blood vessels. We call this the "flight or fight" response. Let's take a typical example: a gazelle sees or hears that a wolf is close by, its brain perceives that danger is lurking and sends signals to make the heart pump fast and hard and to direct blood flow towards skeletal muscles. The cardiovascular system has been prepared so that the gazelle can run away as fast as possible. Once the gazelle arrived to a safer environment, the cardiovascular system "calms down": the heart slows down and pumps less with each beat, blood pressure returns to normal.

The signals received by the driver often tell him or her that danger is lurking and indicate the need to take proper action to avoid an accident. In fact, the main job of a driver is to continuously keep very alert against danger and to do whatever is necessary (adjusting speed, vehicle position, etc.) to arrive safely at the destination. This basic "fight or flight" reaction is activated, but under entirely different circumstances. There is very little physical activity involved, and the threat and need for alertness is continuous as long as the driver is sitting behind the wheel. The cardiovascular system doesn't ever really calm down. This general pattern has been called by Dr. Robert Eliot, one of the world's experts on stress and the heart, as a state of "suspended visceral-vascular readiness" (1979). If this type of stress reaction is repeated over a long time, persistently high blood pressure, or hypertension often results. Dr. Stewart Wolf is another leading expert in stress and the heart. He has investigated the response to very high stress levels in which there is a need to monitor the environment with great alertness while trying to conserve energy, i.e. with minimal physical activity. This can be called the "vigilance response". This places a particularly heavy burden on the cardiovascular system (Wolf 2000).

Laboratory Studies among Professional drivers: Truck drivers show marked vigilance responses
We conducted a series of studies in which the threat avoidant aspects of driving are presented in the laboratory environment, while we monitored the brain's electrical activity (electroencephalogram-EEG) together with cardiovascular responses (blood pressure, finger pulse and electrocardiogram). We did this in various ways: one was by exposure to headlight glare similar to that faced from an on-coming vehicle during night driving. Another was a choice-reaction time task in which the participants were told to imagine that mistakes in their performance could lead to a traffic accident.

We first tested young, apparently healthy professional drivers compared to workers who had no driving experience whatsoever. The drivers had significantly greater elevations in diastolic blood pressure in response to the glare, and showed signs of arousal of the central nervous system (EEG) in both of these laboratory studies (Belkic 1992 a & b). Several truck drivers participated in these studies, and had the most dramatic diastolic blood pressure responses to glare (rising to mean levels of 97.0 mm Hg from baseline of 82.7 mm Hg). The truck drivers also showed a slowing of their heart rate in response to glare, together with an increased blood pressure and diminished blood flow measured in the finger (blood vessel constriction). This type of cardiovascular reaction pattern is typical the above-mentioned vigilance response. All of the truck drivers drove long-routes at night, often on undivided and poorly lit roads, where an on-coming headlight would likely be a greater threat than in urban conditions.

Hypertension among professional drivers
Professional drivers are at very high risk of developing hypertension. The published epidemiologic data consistently show that there is a significant relation between being a professional driver and having elevated blood pressure (Backman 1983, Belkic 1990, Belkic 1992, Ragland 1987, Ragland 1997, Yokoyama). The studies by Backman (1983) and by Yokoyama et al. (1985) have looked specifically at truck drivers.

The above-cited studies are all based upon blood pressure (BP) measurements in the clinic setting. We have recently shown that among working populations, there is a substantial number of people (probably more than one in seven) who have normal BP in the clinic, but high BP during work (Belkic 2000). This is called "occult workplace hypertension", and carries a risk for atherosclerosis and increase in the mass of the left heart ventricle, just like that among people who have persistently elevated BP (Liu 1999). We strongly suspect that there are many professional drivers who have occult workplace hypertension, given their high risk for developing hypertension, and given the BP responses in headlight glare in the laboratory among young professional drivers with normal casual clinic BP.

Unfortunately, there has been relatively little examination of professional drivers' BP during actual work. Sato and colleagues (1999) recorded blood pressure and ECG of 8 male long-route truck drivers. They reported that BP was higher during driving and loading-unloading than during rest or on a non-work day, and that mean ambulatory systolic BP was over 140 mm Hg in 6 of these 8 drivers. We performed a study of 30 male urban mass transit operators with at least 5 years on the job, and with normal clinic BP. We found that particularly while driving the afternoon rush hour as the second half of a split-shift, the drivers' mean diastolic BP was high: 89.4 mm Hg, and that compared to matched clerical workers, their work time BP was significantly greater (effect size = + 7 / + 5 mm Hg). Several of the drivers had persistently elevated BP during the entire 24-hour recording period (Ugljesic 1992). Taken together, these findings demonstrate the importance of examining BP systematically among professional drivers during their actual work.

We have described just a few "econeurocardiac" mechanisms as these relate to the traffic work environment. We've focused upon blood pressure for several reasons. First, hypertension is one of the most important risk factors for stroke and heart attack. High blood pressure can occur without any symptoms whatsoever, it is treatable, and as discussed, is closely related to stress mechanisms that specifically pertain to professional drivers. We provide a more detailed discussion of these and other mechanisms in our recent book: The Workplace and Cardiovascular Disease (eds. Schnall, Belkic, Landsbergis and Baker), 2000; 15(1), published by Hanley and Belfus.

Other neurocardiac mechanisms
Studies looking at other neurocardiac mechanisms are more sparse, especially among truck drivers. Apparies and colleagues (1998) compared heart rate responses among 24 truck drivers while operating three different vehicle types: a single trailer, a triple trailer A-dolly , and triple trailer C-dolly on an 8-10 hour standard route. The fastest heart rates were recorded while driving the most demanding A-dolly. Heart rate increased, and heart rate variability decreased with increased time on the road, a finding which the authors attribute to fatigue. Vivoli and colleagues (1993) examined stress hormones (adrenaline, noradrenaline and cortisol) in three long-route truck drivers during work, and found that adrenaline excretion was especially high during difficult weather and traffic conditions. A study by Hartvig and Midttun (1983) showed elevated cholesterol levels among 52 truck and bus drivers compared to industrial workers, whereas another study among 392 bus and truck drivers showed no significant difference in cholesterol compared to population referents (Hedberg 1993). We recorded 24-hour continuous electrocardiogram (Holter monitoring) among twenty professional drivers, seven of whom were truck drivers, and found significantly more heart arrhythmias when a driving shift was recorded compared to rest days. Lack of sleep, coffee and smoking were significantly associated with these arrhythmias (Belkic 1991). Much more study is needed of these and other neurocardiac mechanisms of heart disease risk among professional drivers.

2. What contributes to cardiac risk among professional drivers?

We believe that the prolonged exposure to the heavy burden of this work represents the key determinant of cardiac risk among professional drivers. There are, in addition, exacerbating factors that heighten the risk even further: some of these are modifiable work stressors such as excessive time pressure and long work hours. Certain behavior patterns, such as repressive coping (denial) and Type A behavior, as well as other activities also appear to contribute, such as smoking, eating heavy meals especially with a high fat content, use of stimulants. However, these other risk factors for heart disease have been shown to be closely related to the stressful working conditions faced by professional drivers.

Explanation (see also answers to questions 4, 6 & 7):
a) Studies comparing professional drivers with hypertension to those with normal BP

In order to try to answer the question as to what contributes to risk of hypertension among professional drivers, we compared a group of twenty-four professional drivers with hypertension to 34 with normal BP (Belkic 1996, Emdad 1997). Using an advanced statistical technique called "multiple logistic regression" we looked for the set of factors which best distinguished these two groups, after controlling for age. First, we found that during the laboratory study, the drivers with hypertension showed a heightened brain wave reaction when they performed the traffic accident avoidance task. This indicates that their attention levels were very high in these situations. On the other hand, the drivers with hypertension most vehemently denied any kind of fear whatsoever when driving. This seems to indicate that denying the difficulty associated with driving puts an extra burden upon the driver's physiology, and could possibly contribute to risk of hypertension. The drivers with hypertension also were significantly more overweight compared to those with normal BP. Obesity is a well-known risk factor for hypertension, and is closely coupled with professional driving. We found a significant association between obesity and number of work hours behind the wheel among professional drivers (Emdad 1998). The final factor which significantly and independently distinguished the drivers with hypertension from those with normal BP, was time pressure on the job. The harmful effect of time pressure upon professional drivers has been shown in several other studies. In city bus drivers time pressure was associated with elevations in the stress hormones, adrenaline and noradrenaline (Evans 1994, Gardell 1983).

Prolonged exposure to professional driving increases risk of hypertension. A study of San Francisco urban transport operators shows that after taking into account age and other important risk factors such as obesity, number of years on that job was significantly and independently associated with risk of hypertension (Ragland 1997).

b) Studies comparing professional drivers with hypertension to those with heart disease
What then are the factors that contribute to the development of full-blown heart disease among professional drivers? We addressed that question by comparing professional drivers with hypertension to thirteen drivers who had suffered a heart attack or other major manifestation of coronary heart disease. They were all under the age of 53. One significant difference was in the number of who had smoked cigarettes; all thirteen drivers with heart disease had done so. They also had a significantly stronger family history of heart disease, and more pronounced Type A behavior. When performing the traffic accident avoidance task, they showed the largest diastolic blood pressure reaction. During exposure to headlight glare, the drivers with heart disease showed the greatest central arousal (EEG) and the longest lasting constriction of finger blood vessels (Belkic 1996, Emdad 1997).

One of the most striking differences, however, and one which acted independently of all the other factors, was long work hours. On the average, the drivers with heart disease worked between 42 and 48 hours per week, and averaged 8.5 hours/day behind the wheel, compared to 6.3 hours among the drivers with hypertension but without manifest coronary heart disease. There is evidence that long work hours are associated with increased risk of heart disease (Buell 1960, Falger 1992, Jenkins 1982). The results of our study suggest that working long hours are particularly harmful for professional drivers. Prolonged exposure to this highly stressful work environment could sensitize the nervous system, leading to dangerous consequences for the cardiovascular system.

3. What do the results of exercise testing of apparently healthy drivers reveal?

Relatively poor levels of physical fitness and elevations in diastolic blood pressure, which could indicate increased risk of hypertension and coronary heart disease.

We performed bicycle exercise testing in 42 young, healthy, male professional drivers and thirty matched building worker referents (Ugljesic 1996). The drivers showed lower physical fitness levels than controls (significantly lower maximum exercise level with higher energy expenditure). Since the two groups were similar with respect to leisure time physical activity, we attribute their poorer physical fitness to being more sedentary on the job. La Dou (1988) also notes that the prolonged periods of sitting in a fixed position may contribute to poor physical fitness among truck drivers.

Compared to the building workers, the professional drivers had significantly higher diastolic blood pressure at the end of exercise (97 +/- 14 versus 79 +/- 19 mm Hg), together with a significantly greater number of diastolic hypertensive reactions (diastolic BP>115mmHg). This type of reaction to exercise suggests an increased risk of hypertension (Kremser 1986). Low physical fitness and diastolic hypertensive reactions to exercise may also be indicators of coronary heart disease risk (Sandvik 1993, Akhras 1991).

4. How does the stress level of drivers compare to other occupations?

The total burden of occupational stress faced by professional drivers is about twice as high as other occupations, such as building trade workers and subway guard attendants. Comparisons show slightly higher total burden among city bus drivers compared to truck drivers. There is, however, a specific set of stressors faced by truck drivers.

a) Quantitative comparisons between professional drivers and other occupations

We focus here upon the objective factors in the work environment. Using the Occupational Stress Index (OSI) (Belkic 1994) a total of 58 stressors have been identified that are important in relation to cardiovascular risk. These include many features inherent to professional driving, namely, threat avoidant vigilant activity, high demands upon the visual system, need for rapid decision-making and action, working in a fixed position in a confined space, exposure to noise, vibration, glare etc. We compared a group of 258 professional drivers of various profiles, to 227 building trade workers and found that the mean total OSI score was over twice as high in the drivers (67.2 +/- 4.3 versus 33.0 +/- 7.9) (Belkic 1995). We also compared a group of mainly urban transport operators with subway guard attendant and found that the total OSI was over twice as high in the former (Belkic 1996, Emdad 1997). Thus, using the Occupational Stress Index, we find that driving epitomizes a stressful occupation bearing the majority of features associated with cardiac risk.

In addition to the inherent stressors in the driver's job, there are many other factors that could be modified to lower the stress burden. These include time pressure, long and irregular work hours, especially driving at night, lack of rest breaks, poor mechanical condition of the vehicle and breakdowns, inadequate heating, air conditioning, cabin isolation, and shock absorption. More latitude in deciding about work schedules and other organizational aspects of the work, as well as improved social interactions and maximum social support are particularly critical.

b) Quantitative Comparisons between truck drivers and city bus drivers: How do they differ?
As we have said, professional drivers as a group are exposed to very high levels of occupational stressors and all have much in common. However, each driver profile also faces a specific set of stressors. We used the OSI to compare 69 truck drivers and 130 city bus drivers. The mean total OSI scores were very high for both groups (65.2 +/- 3.6 and 68.7 +/- 3.8, respectively)(Belkic 1995). One important difference is that city bus drivers face predominantly overload, while truck drivers are exposed to a mixture of underload and overload. This combination is not a healthy one for the nervous system or for the cardiovascular system, as pointed out by stress experts Drs. Marianne Frankenhaeuser, Gunn Johansson (1981) and Lennart Levi (1981). When driving on long routes, truck drivers have a relatively low flow of new information (monotony) and frequently drive alone which is another source of underload as well as social isolation. At the same time, they still must keep their sensory systems (especially visual) on full alert at all times ready to make rapid decisions and actions. This need for sustained vigilant monitoring combined with monotonous road conditions is recognized to be a very important contributor to fatigue during long-distance truck driving (Williamson 1996). An additional source of underload contributing to fatigue is delays and long waiting times, which we found to be frequent occurrences among the truck drivers.

Another important difference is that the truck drivers worked significantly longer hours and were mainly paid by the number of routes driven (two important sources of overload), while the city bus drivers had fewer rest breaks. In his exhaustive chapter on the health of truck drivers, Dr. Joseph La Dou (1988) cites long stretches of time away from home as a major work stressor, which creates disruptions in family life. Furthermore, many truck drivers drive at night. According to a number of studies, night shift work contributes to risk of cardiovascular disease (Boggild 1999, Steenland 2000).

Truck drivers also performed more heavy lifting. The strain of this kind of exertion among tanker and other truck drivers has been demonstrated in studies by Dr. Gudrun Hedberg and colleagues (1985, 1986), and is also described by Dr. LaDou (1988). The truck drivers also drove under more hazardous road conditions (including carried explosive cargo, and undivided poorly lit roads during night driving, as mentioned above), although they reported fewer accidents and vehicle breakdowns than did the city bus drivers. Exposure to hazardous chemicals, especially from diesel exhaust, needs to be taken into consideration: e.g. polyaromatic hydrocarbons, carbon monoxide, and lead. The levels are related to the quality of cabin isolation, mechanical condition/emission levels from the vehicle, use of leaded gases, routes taken, etc. Depending on the nature of the cargo and whether loading and unloading is performed, other exposures may occur. A study by Vainiotalo and Ruonkangas (1999) examined exposure to toluene, benzene, hexane, inter alia, among tank truck drivers during loading and unloading. Finally, the size and configuration of the truck can be important stressors, affecting maneuverability, physical effort of driving and the driver's ability to see other vehicles and participants in the traffic environment.

c) When and where the research was carried out
The research described herein is mainly from Europe and the U.S., and was carried out primarily during the 1980's and 1990's. There are also studies among professional drivers from Canada, Latin America, and Asia. Studies on the health risks among professional drivers (mostly among urban transport operators) began in the 1950's and 1960's. These showed increased risk of ischemic heart disease among urban transport operators in the U.K. and Norway (Morris 1959, Berg 1962).

5. What are the health concerns that drivers should be aware of?

a) Hypertension, cardiovascular disease and stroke
b) Musculoskeletal disorders
c) High smoking prevalence and risk of lung cancer
d) Obesity
f) Fatigue, sleep deprivation, use of stimulants and psychological distress

Before discussing the specific health risks faced by truck drivers, an important concept about occupational health must be kept in mind. This is the "healthy worker effect" (McMichael 1976), leading to an underestimation of disease rates when comparing workers to the general population. This is the case since workers in general, and especially those such as professional drivers who must pass medical certification examinations to begin work and at periodic intervals, turn out to be healthier than the general population which includes sick as well as healthy people. The "healthy worker effect" is especially strong in underestimating cardiovascular disease rates among professional drivers. Important questions include the following: has total work exposure been considered, have retired and disabled workers been included, and what is the referent group with whom comparison is being made.

a) Cardiovascular disease and stroke (see question 1b regarding hypertension)
In 1998 we published a review of the literature concerning heart disease risk among professional drivers (Belkic 1998), compiling earlier reviews of Winkleby et al. [1988], Belkic, et al [1994], and van Amelsvoort [1995]. We found that most of the studies (thirty-four out of forty) showed professional drivers to have an increased risk of hypertension and cardiovascular disease compared to referents from the working or general population. We concluded that such a consistent and large body of data concerning cardiac risk does not appear to exist for any other specific occupational group. It was striking that heart disease often occurred prematurely, such that professional drivers are over-represented among series of young patients who had suffered a heart attack. In a paper by Villarem et al. [1982] of thirty-eight consecutive heart attack patients under the age of 30, 20% were long-route truck drivers. Riecanský et al. [1988] reported that 40% of their series of heart attack patients younger than age forty were professional drivers.

The evidence overall is strongest for urban mass transit operators. A study by Dr. Annika Rosengren and colleagues [1991] shows the increased risk of coronary heart disease to be independent of standard cardiac risk factor status. After a mean of 11.8 years of prospective study, these authors reported an odds-ratio (OR) of 3.3 (95% CI =2.0-5.5) for coronary heart disease in 103 middle-aged male mass transit drivers in Gothenberg with respect to 6596 men from other occupational groups. With accounting for the major standard cardiac risk factors (age, serum cholesterol, blood pressure, smoking, body mass index, diabetes, positive parental history of CHD and physical activity) as well as socio-demographic factors, the risk decreased only slightly (OR=3.0, 95% CI=1.8-5.2).

As to truck drivers, there are fewer studies, and these are not as consistent as for urban transit operators. An analysis of disease rates among U.S. workers shows that truck drivers have among the highest rates of heart attack (Leigh 1998). A study by Dr. Per Gustavsson and colleagues (1996) showed that after considering age, smoking and obesity that long distance-urban (but not the other three) categories of male truck drivers had a significantly increased risk of heart attack, compared to other working men in Sweden. There are also two studies (Luepker 1978 and Balarajan 1988) in which comparisons were made with the general population, in which lower rates of circulatory disease death were found among truck drivers. Dr. van Amelsvoort reporting from the "International Workshop on the Epidemiology of Coronary Heart Disease among European Truck Drivers", points out that in these two studies a strong healthy worker effect was likely. In the latter study only a one time job description was assessed (in 1939) while medical follow-up was made from 1950 to 1984. In the former only unionized truck drivers were included.

Besides the large body of investigations concerning heart disease risk among professional drivers, a fairly recent study of all employed persons aged 20-59 in Denmark reveals that professional drivers are also at an increased risk of stroke. Age-specific hospitalization rates (SHR) showed an SHR=114 (95% CI=108.2 - 120.4) for men and SHR = 130 (95%CI=100 - 168) for women. Some, but not all of the truck driver categories, were at elevated risk (Tuchsen 1997).

b) Musculoskeletal disorders
There is a large body of literature showing high prevalence of musculoskeletal disorders among professional drivers (Backman 1983, Hedberg 1988, Krause 1997a & b). Low back pain is the most common, and has been closely related to exposure to vibration (Magnusson 1996). Among urban transit operators, back and neck pain are significantly related to ergonomic problems such as poor seat adjustment, steering and braking problems, (Krause 1997a), as well as long, uninterrupted hours behind the wheel, and psychosocial problems such as high psychological demands and low supervisor support (Krause 1997b).

As to truck drivers, La Dou (1988) notes that in order to handle a heavy truck and control the large steering wheel, they must sit in a rigid, upright position that, if held for long periods of time, leads to stiffening of the neck, back and muscles of the extremities. Brendstrup and colleagues (1987) report a correlation between length of employment as a fork-lift truck driver and low back pain within the preceding year.

c) High smoking prevalence and risk of lung cancer
Cigarette smoking is very common among truck drivers. Nelson and colleagues (1994) used data from the National Health Interview Surveys to assess smoking prevalence in over 200 occupations in the U.S. In 1987-1990, drivers of heavy trucks were among the twenty occupations with the highest smoking prevalence; a total of 45.8% of drivers of heavy trucks were current cigarette smokers. In contrast, the prevalence of cigarette smoking among adult men in the U.S. is 28% and 25% among adult women (Minna 1997). About 20% of deaths from coronary heart disease and 30% of all cancer deaths are attributed to cigarette smoking (Holbrook 1998). The risk of developing lung cancer is increased about 13-fold by active smoking, and there are likely co-carcinogenic effects of occupational exposures (Ibid). There are several reports in the literature of increased lung cancer rates among various groups of truck drivers (Finkelstein 1995, Hansen 1993, Jakobsson 1997, Rafnsson 1991, Steenland 1990). It is possible that exposure to diesel fumes and motor exhaust, most likely together with cigarette smoking, may contribute to this increased risk.

d) Obesity
Several studies have reported that professional drivers are more obese than workers in other occupations. Hedberg and colleagues (1993) reported a significantly greater mean body mass index (26.3) among a group of bus and truck drivers, compared to 25.9 among working people of other occupations.

e) Peptic ulcer disease
There is one published study on peptic ulcer disease among professional drivers (Netterstrom 1990). Compared to the general population, urban bus drivers in Denmark were found to have twice the incidence of hospitalization for duodenal ulcer disease over 6.75 years of follow-up. Feeling of monotony was a significant predictor of peptic ulcer disease hospitalization among the drivers.

f) Fatigue, sleep deprivation, use of stimulants and psychological distress
Chronic fatigue and sleep deprivation are major problems for truck drivers on long routes. One extremely unhealthy way to keep driving despite exhaustion is to artificially maintain alertness by the use of stimulants--including excessive coffee, amphetamines or other substances. Dr. Joseph La Dou (1988) states that the use of stimulants is widespread among truck drivers, because of the need to stay awake for prolonged periods. This underscores the urgent need to reduce the long work hours that oblige truck drivers to work far beyond the realistic norms of human capacity.

A relation between the stressful working conditions and psychological distress is also found among truck drivers (La Dou 1988, Orris 1997). Dr. Peter Orris and colleagues found that a group of 317 package truck drivers throughout the U.S. showed scores on the SCL 90-R for psychological distress far above the average (91st percentile).

6. What do I consider to be the most important aspects of a driver's health? What are the most effective ways for drivers to remain or become healthy?

a) Avoid prolonged exposure to driving: take regular rest breaks, avoid overtime work, make sure to regularly have days off, take vacations, use that time, whenever possible to be away from traffic and motor vehicles.

b) Strive to maintain a stable family life and social support network of friends and acquaintances.

c) Share your work experiences, including problems, with understanding and supportive colleagues, friends and family. Don't bottle up your frustrations inside. Admit that this is a tough job, and feel proud of performing it well. When faced with overwhelming difficulties, especially accidents, consult competent professionals with whom you feel comfortable.

d) Seek ways to make your work environment and that of your colleagues as favorable as possible (comfortable cabin conditions, vehicle maintenance-minimum emissions, humane work schedules, realistic time-tables, friendly and supportive inter-personal relationships, etc.). (The Job Stress Network: Risk Factors), (The Job Stress Network: Prevention)

e) If you are a non-smoker, remain so. If you are currently a smoker, make smoking cessation your key priority, and don't hesitate to get help in doing so, if needed. (AMA smoking cessation information)

f) In consultation with your primary care clinician, maintain a regular physical activity regimen focusing on dynamic exercise. We consider swimming to be an ideal activity for professional drivers. We recommend that exercise-stress testing be used widely to assess physical fitness level and risk of heart disease among professional drivers. Walk as much as possible, including during rest breaks. (Diet and Exercise: Healthy Balance for a Healthy Heart, Preventing Heart Disease-Cardiac Health Web Homepage)

g) Have regular medical check-ups, especially check BP regularly, if at all possible during work. Regularly check ECG, blood cholesterol (total and LDL fraction), triglyceride and glucose levels, and have a chest x-ray taken periodically.

h) Strive to get adequate sleep. Avoid use of stimulants, including excessive coffee intake. Avoid late night driving, if at all possible. (If nightwork is unavoidable, seek out ways to diminish its negative effects. (See Coping Strategies for Shift Work and Monk 1992)

i) Try to eat a healthy, well-balanced diet, with as regular a meal schedule as possible. Be sure to eat breakfast. Avoid heavy meals before going to sleep. Try to keep fat intake below 25% of your total food intake. Keep high fiber, low-fat, low simple carbohydrate snacks handy. Keep alcohol consumption to a minimum, it is very high in calories, as well as being a risk factor for hypertension. Weigh yourself regularly. For more details on a "heart healthy" diet see: (Diet and Exercise: Healthy Balance for a Healthy Heart, Preventing Heart Disease-Cardiac Health Web Homepage)

j) Avoid using a mobile telephone while driving. This creates an extra burden on attention, and may increase the risk of accidents (Alm 1995).

k) Have interests and activities other than driving. Enjoy nature, music, sports, creative work at home, etc. Rest your eyes whenever possible from activity requiring active attention. Cultivate your ability to relax (See Preventing Heart Disease-Cardiac Health Web Homepage)


Smoking Cessation--Importance and Challenges for Professional drivers

Quitting smoking is a critically important step, which an individual can take to protect his or her overall health. The recovery process begins almost immediately. One year after stopping smoking, the risk of heart attack falls markedly. The risk of tobacco-related cancer also drops. Total mortality among former smokers decreases almost to that of never-smokers 15 years after quitting (Holbrook 1998).

Smoking is closely inter-connected with the professional driver's work environment. In our study of an attempt to help professional drivers quit smoking, those drivers who succeeded in cutting down or quitting smoking almost always had also made some type of improvement in their working life (change in work schedule, route, etc.)(Emdad 1998).

Professional drivers who are heavy smokers face a special challenge, and should receive maximum support and understanding from supervisors, colleagues, family and friends in their efforts to kick the habit. Many drivers will need help from their health providers, and some may want to enroll in a smoking cessation program. They should not hesitate to seek this help (AMA smoking cessation information). Some measures that improve the long-term quit rate of worksite smoking cessation programs include shared company and employee time (Fisher 1990).

We have found that smoking intensity was significantly, and independently predicted by the total score on the Occupational Stress Index (Belkic 1996). This indicates that professional drivers who are the heaviest smokers face the greatest load from potentially modifiable job stressors (e.g. time pressure, special hazards, long work hours, night work or other difficult schedule etc.). Thus, smoking cessation efforts, especially among professional drivers who are heavy smokers, should be fortified by finding ways to improve their working conditions to lower the total stress burden.

In summary, smoking is a major health problem for truck drivers. Overcoming it will require motivation and efforts by drivers themselves, together with supportive actions from the workplace, as well as from the driver's larger social network.

Obesity and Long hours behind the Wheel
Earlier, we alluded to the association between long work hours and obesity, and the relation between the latter and hypertension. In our study of 69 professional drivers, the number of work hours behind the wheel represented a significant, independent predictor of the body mass index. We explained this as follows: "Long driving hours mean more sedentary time. Psychosocial work stressors such as monotony have been associated with excess body weight. It may be that prolonged exposure to traffic-related stressors also triggers overeating. Drivers tend to eat a heavy meal once arriving home after a long workday. Thereafter, due to exhaustion, they often remain sedentary and then fall asleep. Breaking this pattern by changing the work schedule, together with dietary instruction, has resulted in notable weight reduction in individual cases" (p. 236, Emdad 1998). (See Diet and Exercise: Healthy Balance for a Healthy Heart, Preventing Heart Disease-Cardiac Health Web Homepage)

7. Final comments with some practical suggestions and more general measures that are needed

Truck drivers perform a very difficult and responsible job. They are at risk for a number of adverse health outcomes. Systematic efforts aimed at improving their work environment together with aggressive health promotion are needed. We believe that such a preventive approach would be cost-effective: As it now stands, truck drivers are one of the occupational groups with the highest total costs for job-related injuries and illnesses (Leigh 1997).

Some of the measures to create healthier working conditions include improved cabin conditions and ergonometric design (proper isolation, heating and air-conditioning systems, appropriate seat, steering wheel, pedals, dashboard), vehicle maintenance especially to minimize emissions, vibration and noise, realistic time-tables, rational work schedules, with adequate time for rest and recovery. Avoidance of long work hours is of utmost importance. Improvement in road conditions and separate lanes or routes for heavy trucks whenever possible, are also needed. The other participants in traffic should be more aware of the special aspects of truck driving, especially with regard to stopping distance and blind spots.

There are many on-going studies to find the most effective strategies for stress-prevention measures among bus drivers (Kompier 2000). Similar types of studies would be appropriate for truck drivers.

A broad public health approach is needed for truck drivers. A key measure would be the assessment of blood pressure during driving among the largest possible number of truck drivers. Health centers with an expertise in the special problems of professional drivers would be the optimal setting for systematic early detection and prevention of cardiovascular, musculoskeletal and other health problems with a high prevalence among truck drivers, patient confidentiality carefully guarded, and ways to maintain work fitness actively sought. These centers should offer employee assistance programs (EAP), as well as smoking cessation and other health promotional activities.

The truck-stop environment could also be made healthier, by, for example, having restaurants that serve "heart healthy" meals, and by offering exercise facilities. We encourage the readers of RTM to suggest their ideas of what might be done to improve their health and well-being as truck drivers.


Bibliographic References

Akhras F, Jackson G. Raised exercise diastolic blood pressure as indicator of ischaemic left ventricular function. Lancet. 1991; 337:899-900.

Alm H, Nilsson L. The effects of a mobile telephone task on driver behaviour in a car following situation. Accid Anal Prev 1995; 27: 707-715.

Apparies RJ, Rinolo TC, Porges SW. A psychophysiological investigation of the effects of driving longer-combination vehicles. Ergonomics 1998; 41: 581-592.

Backman AL. Health survey of professional drivers. Scand J Work Environ Health. 1983; 9: 30-35.

Balarajan R, McDowall ME. Professional drivers in London: A mortality study. Br J Indust Med 1988; 45: 483-486.

Belkic K, Emdad R, Theorell T. Occupational profile and cardiac risk: possible mechanisms and implications for professional drivers. International Journal of Occupational Medicine and Environmental Health. 1998; 11: 37-57.

Belkic K, Emdad R, Theorell T, Cizinsky S, Wennberg A, Hagman M, Johansson L, Savic C, Olsson K. Neurocardiac mechanisms of heart disease risk among professional drivers. Stockholm: Swedish Fund for Working Life, 1996.

Belkic, K; Ercegovac, D; Savic, C; Panic, B; Djordjevic, M; Savic S. EEG arousal and cardiovascular reactivity in professional drivers. The glare pressor test. Eur Heart J. 1992(a); 13: 304-309.

Belkic K, Gluhak M, Ugljesic M, Mickovic Lj, Sladic R. Prevalence of high blood pressure and electrocardiographic abnormalities among Belgrade mass transit drivers. Revija Rada 1990; 20: 50-60.

Belkic K, Jelic V, Djordjevic M, Mickovic Lj, Ugljesic M. Rhythm disturbances in apparently healthy professional drivers. Kardiologija 1991; 12: 167-170.

Belkic, K; Pavlovic, S; Djordjevic, M; Ugljesic, M; Mickovic, Lj. Determinants of cardiac risk in professional drivers. Kardiologija 1992(c); 13: 145-149.

Belkic, K; Savic, C; Djordjevic, M; Ugljesic, M; Mickovic, Lj. Event-related potentials in professional city drivers: heightened sensitivity to cognitively relevant visual signals. Physiol Behav. 1992(b); 52: 423-427.

Belkic K, Savic C, Theorell T, Cizinsky S. Work Stressors and Cardiovascular Risk: Assessment for Clinical Practice. Part I. Stockholm (Sweden): Stress Research Reports. National Institute for Psychosocial Factors and Health. Section for Stress Research, Karolinska Institute, WHO Psychosocial Center; 1995. Report No.: 256.

Belkic, K; Savic, C; Theorell, T; Rakic, Lj; Ercegovac, D; Djordjevic, M. Mechanisms of cardiac risk among professional drivers. Scand J Work Environ Health 20:73-86; 1994.

Belkic K, Schnall PL, Landsbergis PA, Schwartz JE, Gerber LM, Baker D, Pickering TG. Hypertension at the workplace--An occult disease? The need for work-site surveillance. Submitted 2000.

Berg KJ, Melkild A. Coronary disease in a group of Norwegian tram drivers. Acta Med Scand 1962; 171: 671-677.

Boggild H, Knutsson A. Shift work, risk factors and cardiovascular disease. Scand J Work Environ Health 1999; 25: 85-99.

Buell P, Breslow L. Mortality from coronary heart disease in California men who worked long hours. J Chron Dis 1960; 22: 615-626.

Eliot, R.S. (1979). Stress and the Major Cardiovascular Disorders. Mt Kisco: Futura Publishing Co.

Emdad R, Belkic K, Theorell T, Cizinsky S. What prevents professional drivers from following physicians' cardiologic advice? Psychoth Psychosom In Press.

Emdad R, Belkic K, Theorell T, Cizinsky S, Savic C, Olsson K. Work environment, neurophysiologic and psychophysiologic models among professional drivers with and without cardiovascular disease: Seeking an integrative neurocardiologic approach. Stress Med 1997; 13: 7-21.

Evans GW. Working on the hot seat: urban bus operators. Accid Anal Prev 1994; 22: 181-193.

Falger PRJ, Schouten EGW. Exhaustion, psychologic stress in the work environment and acute myocardial infarction in adult men. J Psychosom Res 1992; 36: 777-786.

Finkelstein MM. Occupational associations with lung cancer in two Ontario cities. American Journal of Industrial Medicine 1995; 27: 127-136.

Fisher KJ, Glasgow RE, Terborg JR. Worksite smoking cessation: a meta-analysis of long-term quit rates from controlled studies. J Occup Med 1990; 32: 429-439.

Frankenhaeuser M, Johansson G. On the psychophysiologic consequences of understimulation and overstimulation. In Levi L. Society, Stress and Disease. Vol. 4 Working life. New York: Oxford University Press, 1981.

Gardell B, Aronsson G, Barklof K. The working environment for local public transport personnel. Stockholm: The Swedish Work Environment Fund, 1983.

Gustavsson P, Alfredsson L, Brunnberg I, Hammar N, Jakobsson R, Reuterwall C, Östlin P. Myocardial infarction among male bus, taxi, and lorry drivers in middle Sweden. Occupational and Environmental Medicine 1996; 53: 235-240.

Hansen ES. A follow-up study on mortality of truck drivers. Am J Indust Med 1993; 23: 811-821.

Hartvig P, Midttun O. Coronary heart disease risk factors in bus and truck drivers. Int Arch Occup Environ Health 1983; 52: 353-360.

Hedberg GE. Physical strain in Swedish lorry drivers engaged in the distribution of goods. J Human Ergol 1985; 14: 33-40.

Hedberg GE. The period prevalence of musculoskeletal complaints among Swedish professional drivers. Scand J Soc Med. 1988 ; 16: 5-13

Hedberg GE, Jacobsson KA, Janlert U, Langendoen S. Risk indicators of ischemic heart disease among male professional drivers in Sweden. Scand J Work Environ Health 1993; 19: 326-333.

Hedberg GE, Niemi KJ. Physical and muscular strain in Swedish tanker truck drivers. Ergonomics 1986; 29: 817-826.

Holbrook JH. Nicotine addiction. In: Fauci AS, Braunwald E, Isselbacher KJ, Wilson JD, Martin JB, Kasper DL, Hauser DL, Longo D. (eds.) Harrison's Principles of Internal Medicine. 14th Edition. New York: McGraw-Hill, Inc. 1998, pp. 2516-2519.

Holme I, Helgeland A, Hjermann I, Leren P, Lund-Larsen PG. Coronary risk factors in various occupational groups: The Oslo Study. Br J Prev Soc Med 1977; 3l: 96-100.

Jakobsson R, Gustavsson P, Lundberg I. Increased risk of lung cancer among male professional drivers in urban but not rural areas of Sweden. Occupaitonal and Environmental Medicine 1997; 54: 189-193.

Jenkins CD. Psychosocial risk factors for coronary heart disease. Acta Med Scand 1982; 660 (Suppl.): 123-136.

Kompier MAJ, Aust B, van den Berg A-M, Siegrist J. Stress prevention in bus drivers: Evaluation of 13 natural experiments. Journal of Occupational Health Psychology 2000; 5. 11-31.

Krause N, Ragland DR, Greiner BA, Fisher JM, Holman BL, Selvin S. Physical workload and ergonomic factors associated with prevalence of back and neck pain in urban transit operators. Spine. 1997(a); 22: 2117-2127.

Krause N, Ragland DR, Greiner BA, Syme SL, Fisher JM. Psychosocial job factors associated with back and neck pain in public transit operators. Scand J Work Environ Health 1997(b); 23: 179-186.

Kremser CB, Rajfer SI. The normal cardiovascular response to exercise. In AR Leff (ed.) Cardiopulmonary exercise testing. Grune & Stratton, Orlando, 1986, pp. 107-121.

LaDou J. The health of truck drivers. In: C Zenz (ed.). Occupational Medicine: Principles and practical applications. Year Book Medical Publishers, Chicago, 1988, 2nd Edition, pp. 958-970.

Leigh JP, Miller TR. Ranking occupations based upon the costs of job-related injuries and diseases. Journal of Occupational and environmental Medicine. 1997; 39: 1170-1182.

Leigh JP, Miller TR. Occupational illnesses within two national data sets. International Journal of Occupational & Environmental Health. 1998; 4: 99-113.

Levi L. Preventing Work Stress. Reading: Addison-Wesley Publishing Co., 1981.

Liu J, Roman M, Pini R, et al. Cardiac and arterial target organ damage in adults with elevated ambulatory and normal office blood pressure. Ann Intern Med 1999; 131: 564-572.

Luepker RV, Smith ML. Mortality in unionized truck drivers. J Occup Med 1978; 20: 677-682.

Magnusson ML, Pope MH, Wilder DG, Areskoug B. Are occupational drivers at an increased risk for developing musculoskeletal disorders? Spine 1996; 21: 710-717.

McMichael AJ. Standardized mortality ratios and the "healthy worker effect". Scratching the surface. J Occup Med 1976; 18: 165-168.

Minna JD. Neoplasms of the lung. In: In: Fauci AS, Braunwald E, Isselbacher KJ, Wilson JD, Martin JB, Kasper DL, Hauser DL, Longo D. (eds.) Harrison's Principles of Internal Medicine. 14th Edition. New York: McGraw-Hill, Inc. 1998, pp. 552-562.

Monk TH, Folkard S. Making shiftwork tolerable. Taylor & Francis, London 1992.

Morris JN. Occupation and coronary heart disease. Arch Intern Med 1959; 104: 77/903-81/907.

Nelson DE, Emont SL, Brackbill RM, Cameron LL, Peddicord J, Fiore MC. Cigarette smoking prevalence by occupation in the United States. A comparison between 1978 to 1980 and 1987 to 1990. Journal of Occupational Medicine 1994; 516-525.

Netterstrøm, B., Juel, K. Peptic ulcer among urban bus drivers in Denmark. Scand J Soc Med 1990; 18:97-102.

Orris P, Hartman DE, Strauss P, Anderson RJ, Collins J, Knopp C, Xu Y, Melius J. Stress among package truck drivers. American Journal of Industrial Medicine 1997; 31: 202-210.

Rafnsson V, Gunnarsdóttir H. Mortality among professional drivers. Scand J Work Environ Health 1991; 17:312-317.

Ragland DR, Greiner BA, Holman BL, Fisher JM. Hypertension and years of driving in transit vehicle operators. Scand J Soc Med 1997; 25: 271-279.

Ragland D, Winkelby MA, Schwalbe J, Holman BL, Morse L, Syme SL, et al. Prevalence of hypertension in bus drivers. Int J Epidemiol 1987; 16:208-14.

Riecansky J, Milichercik J, Kasper J, Zelenay J, Havlinova K. Myocardial infarction at young age. Czech Med 1988; 11: 123-130.

Rosengren A, Anderson K, Wilhelmsen L. Risk of coronary heart disease in middle-aged male bus and tram drivers compared to men in other occupations: A prospective study. Int J Epidemiol 1991; 20: 82-87.

Rusconi C, Arosio G, Orlando G, Petroboni V, Riva S, Gola E, et al. Coronary risk factors and ischemic cardiopathy in bus drivers and conductors. Minerva Cardioang 1975; 23: 718-727.

Sandvik L, Erikssen J, Thaulow E, Erikssen G, Mundal R, Rodahl K. Physical fitness as a predictor of mortality among healthy, middle-aged Norwegian men. N Engl J Med 1993; 328: 533-537.

Sato S, Taoda K, Wakaba K, Kitahara T, Nishiyama K. Effect of long distance truck driving in Hokkaido on the cardiovascular system. Sangyo Eiseigaku Zasshi. 1999; 41: 206-216.

Schnall PL, Belkic K, Landsbergis PA, Baker D. (eds.) The Workplace and Cardiovascular Disease. Occupational Medicine: State of the Art Reviews. 2000; 15.

Steenland K. Shift work, long hours and cardiovascular disease: A review. In: Schnall PL, Belkic K, Landsbergis PA, Baker D. (eds.) The Workplace and Cardiovascular Disease. Occupational Medicine: State of the Art Reviews. 2000; 15: 7-17.

Steenland NK, Silverman DT, Hornung RW. Case-control study of lung cancer and truck driving in the Teamsters Union. American Journal of Public Health. 1990; 80: 670-674.

Tüchsen F. Stroke morbidity in professional drivers in Denmark 1981-1990. Int J Epidemiology. 1997; 26: 989-994.

Ugljesic M, Belkic K, Boskovic S, Avramovic D, Mickovic Lj. Increased arterial blood pressure during work and risk profile among high-stress occupations: Journalists and city mass transit drivers. Kardiologija. 1992; 13: 150-154.

Ugljesic M, Belkic K, Boskovic D, Boskovic S, Ilic M. Exercise testing of young, apparently healthy professional drivers. Scand J Work Environ Health 1996; 22: 211-215.

Vainiotalo S, Ruonkangas A. Tank truck driver exposure to vapors from oxygenated or reformulated gasolines during loading and unloading. American Industrial Hygiene Association Journal. 1999; 60: 518-525.

van Amelsvoort LGPM. Coronary heart disease among truckdrivers. Report of the International Workshop on the Epidemiology of Coronary Heart Disease among European Truck Drivers. Bilthoven, European Commision, 1995.

Villarem D, Thieuleux FP, LaBlanche JM, Tilmant PY, Bertrand M. Myocardial infarction in subjects less than 30 years of age. Ann Cardiol Angeiol 1982; 31: 263-268.

Vivoli G, Bergomi M, Rovesti S, Carrozzi G, Vezzosi A. Biochemical and haemodynamic indicators of stress in truck drivers. Ergonomics 1993; 36: 1089-1097.

Williamson AM, Feyer A-M, Friswell R. The impact of work practices on fatigue in long distance truck drivers. Accid Anal Prev 1996; 28: 709-719.

Winkleby, MA; Ragland, DR; Fisher, JM; Syme SL. Excess Risk of Sickness and Disease in Bus Drivers: A Review and Synthesis of Epidemiological Studies Int J Epidemiol 1988; 17: 255-262.

Wolf S. The environment-brain-heart connection: Econeurocardiology In: Schnall PL, Belkic K, Landsbergis PA, Baker D. (eds.) The Workplace and Cardiovascular Disease. Occupational Medicine: State of the Art Reviews. 2000; 15: 107-109.

Yokoyama E, Teru S, Mijake T, Mashita M, Tsuchihasi M, Ariga T, et al. Health care of truck drivers with reference to blood pressure control. Nihon Univ J Med 1985; 27: 225-238.

For more information regarding this site, e-mail us at: