Metabolic syndrome and the 10-year cardiovascular disease risk in urban public transport drivers in the context of occupational risks and workloads

. The specific risks and workloads of urban public transport drivers create a net for the development of several health issues. It is worth mentioning the impact of the work regime on this type of workers’ metabolic and cardiovascular health. This paper represents a sequence from an ample study that has followed the effects of this professional activity on worker’s health and work capacity and has established prevention / reduction of identified risk factors measures. The health state analysis was realized through a prevalence study on three cohorts (bus, tram, trolleybus drivers). The prevalence of metabolic syndrome was the highest in the group of the bus drivers, 16.7%. The 10-year fatal cardiovascular disease risk in both the increased risk category and very increased risk category was the highest in the trolleybus drivers’ cohort, 29%, respectively 6%. Major contributing pathology, such as hypertension and type II diabetes, starts in the 36-45 years of age group regardless of gender in all three cohorts signalizing an early wear and is already important in the 46-55 years of age group.


Introduction
The exposure to specific risks factors and workloads in the proffesional driving activity of the urban public transport drivers has several types of effects on health such as the musculoskeletal disorders (MSD's), obesity, metabolic syndrome, hypertension, type II diabetes mellitus, cardiovascular, gastro-intestinal and respiratory disorders, hearing and vision problems [1][2][3].
This paper presents a sequence from a large ergonomic study which aims to highlight the risk and workload factors for public transport drivers and their main effects on health, the evaluation of workload, work related stress, and the establishment of prevention / reduction measures of identified risk factors.The related to occupational risks and workloads health status of 201 bus drivers, 127 tram drivers and 64 trolleybus drivers selected on age, gender, seniority and seniority at work criteria was analyzed through a cross-sectional, prevalence study.Regarding the age of participants, the most consistent category was 41-50 years old in all three studied groups.Regarding the seniority, for the majority of participants it was between 20 and 30 years [4].The health status of electric transport women drivers, a minority in this professional activity and 83 persons in the entire urban public transport society, was adressed in this paper.
Considering the impact of cardiovascular morbidity and mortality on workers as individuals but also on traffic safety, this paper shows the estimates for the 10-year fatal cardiovascular risk in three types of public urban drivers: bus, tram and trolleybus drivers and compares the high and very high risk categories between the three lots.The European SCORE with country adjustment for Romania was used for cardiovascular risk estimation.The prevalence of hypertension, type II diabetes and metabolic syndrome as major contributors to cardiovascular disorder, were analized in the three studied lots.

Background
Metabolic syndrome, a cluster of conditions that occur together 2 and increase the risk of cardiovascular disease and type II diabetes, is quite common in this type of workers.This fact is due to the important sedentarism generated by the sedentary work position, the nutritional imbalance as a result of the atypical schedules, the failure to take a meal break to make up for delays, etc. Metabolic syndrome is associated with both the development of hypertension and an increased risk of adverse cardiovascular outcomes [5].
Cardiovascular heart disease is the most common cause of death worldwide as a reflection of rapid epidemiologic transition particularly in low and medium income countries [6][7].Deaths from cardiovascular disease account for as much as 43.7% of all deaths in Europe and Central Asia [7].On the other hand, the last epidemiologic shift is towards obesity and physical inactivity, with type II diabetes, hypertension and lipids anormalities on the rise.Ischemic heart disease (IHD) is the most common, serious, chronic, life-threatening disorder in United States.Genetic factors, energy-rich diet, smoking and a sedentary lifestyle are associated with it.Obesity, insulin resistence, and type II diabetes mellitus are increasing and are powerful risk factors for IHD [6].Elevated blood pressure 3 [6] is an early indicator of epidemiologic transition.Worldwide, 55% of stroke-related deaths and 55% of IHD-related deaths are attributable to sub-optimal systolic blood pressure control [7].Regarding the situation in Romania, the first cause of mortality is cardiovascular disease.Ischemic disease incidence was higher in urban areas and a lot bigger for women in the year 2020.Ischemic heart disease mortality represented in 2020 around 22% of all deaths.Cerebro-vascular diseases incidence was a lot bigger for women in 2020.Cerebro-vascular diseases mortality represented in 2020 around 16% of all deaths [8].
Ischemic heart disease has been related with professional driving in many studies [9][10][11][12].An increased risk for miocardial infarction as well as other cardiac ischemic pathologies are encountered in professional drivers (eg, in the bus drivers this risk increases at 10 years of seniority at work).Regarding stroke, it seems that the ischemic type rather than the hemoragic one is increased in public transport drivers [13].
Another pathology encountered in the professional drivers is sleep apnea syndrome that is an exacerbating factor for hypertension, it is associated with an increased risk of coronary arteries disease, atrial fibrillation, stroke and needs to be promptly treated [14].
Potential mechanisms by which occupational stress may lead to coronary arteries disease include dysregulation of the hypothalamic-pituitary-adrenal axis and hypercortisolism, dysregulation of autonomic nervous system and increased epinephrine, long term activation of the sympatic nervous system and cardiovascular reactivity, dysregulation of coagulation with a prothrombotic state and fibrinolysis dysfunction (increased fibrinogen is an important predictor in miocardial infarction), production of pro-inflammatory cytokines and upregulation of inflammatory cells, and the last, but not least, maladaptive behaviors such as smoking, compulsive eating, physycal inactivity, alcohol consumption and low compliance with treatment.Finally, all these mechanisms converge towards endothelial dysfunction and atherosclerosis [15,14].
Shift work dysrupts circadian rhythm having consequences on carbohydrate and lipid metabolism, inflammation and autonomic nervous system.Atherosclerosis, dyslipidemia and 2 The criteria for the metabolic syndrome were in accordance with NCEP ATP III -3 or more of the 5 items -: -Abdominal obesity (waist circumference ˃102 cm in men and ˃88 cm in women) -Elevated triglycerides ≥150 mg/dl -Reduced HDL cholesterol ˂40 mg/dl in men and ˂50 mg/dl in women -Elevated blood pressure ≥130/85 mmHg -Fasting glucose ≥100 mg/dl 3 Systolic blood pressure ˃120 mmHg, diastolic blood pressure ˂80 mmHg * corresponding author: diacris8@gmail.cominsulin resistence can occur.A predisposition to metabolic syndrom is next.After 5 years of shift work, an increase in coronary arteries disease morbidity and in cardiovascular and coronary arteries disease mortality has been found and the increase continues to grow by 7% at every supplementary 5 years [16].
A medical situation of the urban public transport society about the bus and electric drivers from the last five years prior to the present study has shown that in both men and women, hypertension and type II diabetes prevalence had an increasing trend, the values being generally higher for the electric transport drivers.

Methodology
The methodology of the whole study was complex, ergonomic [4] and mainly followed: -Technical-organizational and psychophysiological analysis of the activity for the studied groups and the conditions for carrying out the activity, -Evaluation of physical and neuropsychic work related effort, of the workloads and work related stress, -Analysis of the physical and mental health.The health state analysis was realized through a prevalence study on three cohorts (bus, tram, trolleybus drivers).The medical data was collected in order to determine the prevalence of metabolic syndrome, hypertension and type II diabetes and the SCORE charts [14] were used for the estimation of the 10-year fatal cardiovascular disease risk.The health state analysis was integrated in the specific work regime of this proffesional activity, -Establishment of prevention / reduction measures of risk factors and workloads.Choosing the package of techniques and tools (programs / scales / their individual elements) was made according to the stages of the study (e.g.TLX index for effort in carrying out the work task -TLX NASA)

Results and discussion
The global risk level evaluation shows that the investigated personnel is subject to an accumulation of occupational risk and workload factors.The major risk is represented by the road risk potentiated by specifics of urban traffic, the heavy traffic, weather conditions, the time at traffic lights, poor discipline in traffic, some passengers behaviour, poor infrastructure etc.Other risks are the physical, environmental, psychosocial and the ergonomic conditions of activity.A specific work regime consisting of physical demands like prolonged sitting posture, ergonomic deficiencies of the driving post, exposure to traffic noise and air pollution, thermal discomfort, even thermal stress in the driver's cabin (especially for tram and trolleybus), working on shifts, sometimes too long working hours, repetitive activity with increased level of vigilance, with permanent retrieval of information, with significant mental effort, the content of activity and its specific workloads (sensory-mental, cognitiv and emotional effort), the increased resposability in relation to traffic and passengers safety, busier traffic, time pressure, work-family life imbalance, lack of autonomy, sometimes conflicting and contradictory requirements, decreased social support from the superiors, contribute to the metabolic and cardiovascular status of these workers [4].The already establised occupational stress can contribute to unhealty behaviors like smoking, uncontrolled eating, alcohol consumtion and poor compliance to treatments and is a cardiovascular risk modifier that multiplies the risks at treshold by a number between 1.2 and 2 [17].In fact, we can define the work regime as the sum of the specific risk factors and workloads that create a structure which acts as a matrix for the development or progression of several health problems, in this case, the metabolic and cardiovascular ones.
From the evaluation of work related effort based on the subjective evaluation indicators (TLX-NASA) a high perceived level of total work related effort (TE) was obtained in all three studied groups.A high level of mental demands (MD), followed in descending order by temporal demands (TD) and physical demands (PD) were main contributors to the total * corresponding author: diacris8@gmail.comwork related effort in all three groups.The professional performance (PP) was in accordance with professional requirements, without contributing to additional effort.The frustration (Fr), as a state of tension felt during the work task performance, registered a medium level [4].
The following medical results were obtained in the studied groups: In the case of the trolleybus drivers' lot, the distribution of hypertension and type II diabetes was as follows:

Metabolic syndrome
No. of people 6 % 11.538% The distribution of 10-year fatal cardiovascular disease risk in the trolleybus drivers group (people over 40 years old) was as such:

High risk Very high risk
No. of people 34 15 3 % 65% 29% 6% While the majority of trolleybus drivers were in the low and moderate risk category, the most of them falled in the moderate risk zone.The percentages of the high risk category, respectively very high risk category were significant. 4t should be noticed the multiplying action of the cardiovascular risk modifiers on the absolute cardiovascular risk determined by SCORE at threshold values.Such risk modifiers are the familial history of premature cardiovascular disorder (at the 55 years of age in men, respectively 65 in women), psihosocial risk factors generators of stress (e.g.occupational chronic stress can multiply by 1.5 the absolute risk of coronary arteries disease in men), obesity and metabolic syndrome, lack of physical activity, autoimmune disorders (e.g.rheumatoid arthritis, ankylosing spondylitis can multiply the absolute risk by 1.5), sleep apneea syndrome (it can multiply the risk by 1.7).[14] Regarding the tram drivers'group, the following distribution of hypertension and type II diabetes was obtained: https://doi.org/10.1051/matecconf/202438900063SESAM 2023 * corresponding author: diacris8@gmail.comThe hypertension and type II diabetes begin to show up in the 36-45 group age of tram drivers which can suggest early wear.The hypertension percentage of the tram drivers in this age group is significantly higher than the one of trolleybus drivers in the same age group (19.4% versus 7.7%), while the type II diabetes percentage is a little higher in the case of tram drivers.The percentages increase with age in the tram group, having significant values.In the 46-55 age group, the percentage of hypertension is higher for tram than for trolleybus drivers (42.6% versus 37.5%), while the type II diabetes is a bit higher for trolleybus than for tram drivers (18.75% versus 18%).At over 56 years of age, the percentages of both hypertension and type II diabetes are the highest presumably due to both age and professsional wear.In the all age group, the percentages of hypertension are similar in trolleybus and tram drivers (32.8% versus 32.3% ), whereas the type II diabetes is higher for the trolleybus than tram drivers (20.3% versus 14.2%).
In the tram drivers group over 40 years old, the following percentage of metabolic syndrome was obtained: The same percentage of the metabolic syndrome was obtained in both the trolleybus and tram drivers groups, around 12%.
Regarding the distribution of the 10-year fatal cardiovascular disease risk in the tram drivers lot the following results were obtained:

High risk Very high risk
No. of people 81 20 2 % 79% 19% 2% In the tram drivers group, it should be noticed too that the majority of people falled in the moderate cardiovascular risk zone.The percentages of high and very high 10-year mortality through cardiovascular diseases risk are lower than in the group of trolleybus drivers (19% versus 29%, respectively 2% versus 6%), but still significant; this can be explained in part by the higher type II diabetes percentage in trolleybus drivers.
Women situation, tram and trolleybus drivers only and a minority in this type of professional activity, is as follows: * corresponding author: diacris8@gmail.comIn the case of electric transport women driver, hypertension and type II diabetes start in the 36-45 age group, which can signal early wear.In the 46-55 age group the percentages of hypertension and type II diabetes are already important and the ischemic heart disease shows up.The percentages of pathology are the highest at an age over 56 years old showing age and professional wear as the possible culprits.In the all-age group, the percentages of hypertension are 29%, of type II diabetes are 14% and of ischemic heart disease are 5%.
The last cohort in this study, the bus drivers' lot, had the following results: In the bus drivers group, it can be again noticed that the pathology starts in the 36-45 age group which can suggest an early wear.The percentage of hypertension in this age group is similar with the corresponding one in trolleybus drivers' (7.5% versus 7.7%), while is the highest in tram drivers (19.4%).The percentage of the type II diabetes in this age group is much lower than that in tram (8.3%) or trolleybus drivers (7.7%).The pathology percentages increase with age and have significant vallues.In the 46-55 age group, the hypertension percentage became the biggest in bus drivers group (50.5% versus 42.6% in tram, respectively 37.5% in trolleybus), whereas the type II diabetes percentage remain higher in trolleybus (18.7%) and tram (18%), than in bus drivers (15.2%).At over 56 years of age, the bus drivers group shows the highest percentages of pathology due to both age and professional wear.In the all age group, the hypertension percentage is the highest in the bus group (39.3%) than in the other two groups (32.8 for trolleybus and 32.2% for tram), while the biggest percentage of type II diabetes remained in the trolleybus group (20.3% versus 15.4% in bus and 14.2% in tram).
The percentage of metabolic syndrome in the bus drivers over 40 years old, was as such:

Metabolic syndrome
No. of people 29 % 16.763%In case of the bus drivers, the metabolic syndrome percentage is the highest, around 17% versus trolleybus and tram drivers where metabolic syndrome is around 12%.
Regarding the 10-year fatal cardiovascular disease risk in the bus drivers lot, the following results were obtained: A comparison between the three profesional drivers groups in what concerns the 10-year fatal cardiovascular disease risk shows the followings results in tabular and grafic forms:  The contributing pathology to the high and very high-risk group in a decreasing order of frequency was type II diabetes, coronary arteries disorder, peripheral arteries disorder, stroke and chronic kidneys disease; other contributors were dyslipidemia, smoking and of course, age.
Both occupational stress and working in shifts seem to be predictors of metabolic syndrome.Moreover, it has been shown that occupational stress in its job strain model, which can be applicable to the present study, is an independent predictor of metabolic syndrome [15][16].
Considering the facts that psychosocial stress is associated in a dose-response pattern with the development and progression of cardiovascular disease independent of conventional risk factors and gender [17], and shifts work is associated in a dose-response pattern with the risk of cardiovascular events [16] it is possible that the high and very high cardiovascular risk in the three studied groups to be even more importantly represented.
The increased prevalence of hypertension and type II diabetes in both men and women public transport drivers should be related to the increase in their risk of developing a cardiovascular disease.Big longitudinal studies such as Framingham 5 have shown the association between hypertension, coronary heart disease, stroke and congestive heart failure.Hypertension-linked primary morbidity is especially related to systolic blood pressure, even with isolated border systolic blood pressure or high-normal blood pressure.Treatment of hypertension decreases the cardiovascular risk [14].
The present study has shown that the first most frequent association was between the total cholesterol value and elevated blood pressure (systolic blood pressure ˃120 mm Hg) [5][6].Occupational stress in its job strain model, which can be applicable to the present study, was 5 Long-term, ongoing cardiovascular cohort study, now on its third generation of participants The distribution of the 10-year fatal cardiovascular risk in the following four risk categories in the three studied lots * corresponding author: diacris8@gmail.comlinked with increase in serum cholesterol levels at 5-year follow-up and in a dose-response pattern with increases in blood pressure that maintained also after work [15].According to Framingham study, the risk to develop a cardiovascular disease as well as the morbidity and mortality after the development of disease, is higher in women with type II diabetes than in men with diabetes.Even if there is no diabetes, the presence of an increased glycaemia or A1c hemoglobin 6 function as a more powerful cardiovascular risk modifier in women than in men [14].This aspect should be considered, regarding the fact that electric transport women drivers have showed a significant percentage of diabetes.

Fig. 1 .
Fig. 1.The graph of the 10-year fatal cardiovascular risk distribution in the three professional drivers lots

Table 1 .
The distribution of HTN and type II diabetes in the trolleybus drivers group In the trolleybus group, it can be noticed that the pathology starts to show up from the 36-45 age group which can suggest an early wear.The percentages of hypertension and diabetes increase with age, with the biggest values at ages over 56; the obtained percentages can come from age and professional wear, but also from the small number of people involved.The percentage of metabolic syndrome in trolleybus drivers' lot (people over 40 years old) was:

Table 2 .
The percentage of metabolic syndrome in the trolleybus drivers group

Table 3 .
The distribution of 10-year fatal cardiovascular risk in the trolleybus drivers group

Table 4 .
The distribution of hypertension and type II diabetes in the tram drivers group

Table 5 .
The percentage of metabolic syndrome in the tram drivers group

Table 6 .
The distribution of the 10-year fatal cardiovascular disease risk in the tram drivers group

Table 7 .
Hypertension, type II diabetes and ischemic heart disease in electric transport women driver (tram and trolleybus):

Table 8 .
The distribution of the hypertension and type II diabetes in bus drivers group

Table 9 .
The percentage of metabolic syndrome in the bus drivers group

Table 10 .
The distribution of 10-year fatal cardiovascular disease risk in the bus drivers group It should be noted than in the category of low and moderate risk in the bus drivers, the majority belongs to the moderate risk.The percentage of the high and very high risk remains the biggest for the trolleybus drivers (29%, respectively 6% versus 25%, respectively 3% in the bus and 19%, respectively 2% in the tram drivers).

Table 11 .
The distribution of 10-year fatal cardiovascular disease risk in the three professional drivers