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 Table of Contents  
Year : 2020  |  Volume : 9  |  Issue : 3  |  Page : 102-106

Coronary artery disease among young drivers (<40 years): Occupational hazard or air pollution driving it?

1 Department of Cardiology, Sri Jayadeva Institute of Cardiovascular Sciences and Research, Bengaluru, Karnataka, India
2 Department of Cardiology, Vijan Hospital, Nashik, Maharashtra, India

Date of Submission25-May-2020
Date of Acceptance21-Jul-2020
Date of Web Publication26-Sep-2020

Correspondence Address:
Dr. Laxmi H Shetty
Department of Cardiology, Sri Jayadeva Institute of Cardiovascular Sciences and Research, Bengaluru, Karnataka
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/JCPC.JCPC_35_20

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Aims: To study clinico-social, biochemical and angiographic profile of patients presenting with premature coronary artery disease (PCAD) who are drivers by profession. To highlight the impact of occupational hazard and air pollution in them. Subjects and Methods: Of 3450 patients registered in the PCAD registry till date, 755 (21.88%) were found to satisfy the inclusion criteria. The data was analyzed by statistical software R version 3.5.0. Further analysis of smokers versus nonsmokers was done. Results: The average age of the group was 33.10 years. Almost all 754 (99.8%) were males, of which 323 (42.78%) smoked. The group had 83 (10.95%) diabetics and 71 (9.4%) hypertensives. Around 99 (13.11%) had a family history of coronary artery disease (CAD). Majority of them, 440 (58.27%), were urban drivers with average driving of 10 h/day. In the group, 482 (63.8%) had abnormal body mass index (BMI) and 539 (71.41%) had abdominal obesity. Low HDL was seen in 508 (67%) patients. ST-elevation myocardial infarction was the most common presentation in 415 (54.96%). Obstructive atherosclerotic CAD was seen in 217 (34.22%). Further analysis of smokers versus nonsmokers showed that hypertension, diabetes, and abnormal BMI were less common among nonsmokers, indicating the probable role of air pollution in them. Conclusions: Occupational hazard due to the stress related to prolonged driving hours, obesity, smoking and the possible role of air pollution are the important cardiovascular (CV) risks which come to light in this group of patients. Furthermore, the majority of them presented with predominant thrombotic lesions, however, smokers, who also had other CV risk factors, presented more often with obstructive atherosclerotic CAD.

Keywords: Air pollution, driver, occupation and heart disease, premature coronary artery disease, prospective observational study

How to cite this article:
Patil RS, Shetty LH, Vijan V, Cheekatla LN, Thomas TJ, Singh H, Raghu T R, Manjunath C N. Coronary artery disease among young drivers (<40 years): Occupational hazard or air pollution driving it?. J Clin Prev Cardiol 2020;9:102-6

How to cite this URL:
Patil RS, Shetty LH, Vijan V, Cheekatla LN, Thomas TJ, Singh H, Raghu T R, Manjunath C N. Coronary artery disease among young drivers (<40 years): Occupational hazard or air pollution driving it?. J Clin Prev Cardiol [serial online] 2020 [cited 2022 Jan 18];9:102-6. Available from: https://www.jcpconline.org/text.asp?2020/9/3/102/296185

  Introduction Top

Premature coronary artery disease (PCAD) by definition occurs at a younger age (before the age of 55 years in men and 65 years in women).[1] In its severe form, PCAD occurs below the age of 40 years.[2]

Atherosclerosis is a chronic inflammatory condition that starts from young age itself.[3] Studies have shown that atherosclerotic plaques or their precursors could be seen even in children younger than 10 years.[4] During later life, the effects of a sedentary lifestyle, coupled with unhealthy nutrition, smoking, alcohol consumption, obesity, and family history of cardiovascular (CV) disease, accelerates atherosclerotic disease.[4] Recently, air pollution is also emerging as a major CV risk factor.[5],[6]

There are two important aspects to be considered among drivers. First, the occupational hazard associated with long and irregular driving hours and second the impact of air pollution over and above the conventional CV risks in them.

Occupational hazard

Drivers are commonly exposed to many unhealthy working conditions such as long hours, irregular shift work, sleep disturbances, stressful conditions, and harmful exposures to environmental pollution.[7],[8],[9],[10],[11] Furthermore, prolonged sitting and physical inactivity can lead to the development of hypertension, diabetes mellitus, and obesity.[12],[13],[14],[15] Drivers are classified as a high-risk group for work-related stress.[16] Many studies have recently confirmed certain relationships between occupational stress, hypertension, and heart diseases.[17],[18]

Air pollution

Recently, many epidemiological and clinical studies have increasingly shown that air pollution is associated with an increased CV disease risk.[6],[19] The most important link between air pollution and heart disease is the particulate matter (PM). The constituents of air pollution are PM PM 2.5 and PM 0.1 particles with aerodynamic diameters (Ads) <2.5 and <0.1 μm, respectively. These penetrate the alveolocapillary membrane of the lung and enter the bloodstream.[20],[21] There they can cause an increase in heart rate, blood pressure, fibrinogen, and blood coagulation factors. They also increase inflammatory mediators like C-reactive protein) and decrease the heart rate variability, which in turn causes myocardial ischemia, malignant ventricular arrhythmias, increased acute clot formation triggering acute coronary syndromes.[20],[21] Furthermore, long-term exposure to environmental pollutants increases the probability to develop atherosclerosis and ischemic heart disease.[10],[11],[22]

There are several studies highlighting the CV risk, occupational stress, and air pollution in drivers. However, there is a paucity of data on drivers presenting with PCAD. What drives it, is it only occupational stress? and or air pollution? needs to be answered. Identifying the high-risk factors among occupational drivers is very important for the early detection and prevention of CV diseases, more so PCAD. Hence, the study is an attempt to answer some of these questions and bring forward the risk factors favoring occupational stress and air pollution.

Settings and design

PCAD Registry is a Prospective ongoing descriptive observational study in Indian populations <40 years of age with Coronary Artery Disease (CAD). It was started on April 1, 2017.

  Subjects And Methods Top

The PCAD registry is a prospective multisite descriptive observational study examining a cohort of young Indian adults aged ≤40 years with CAD, from the point of index admission to a period of 5 years. This is registered under the Clinical Trials Registry of India (CTRI/2018/03/012544).

This registry included all patients with index admission for ischemic heart disease, as proven by:

  1. Documented episode of the acute coronary syndrome and
  2. Chronic stable angina with documented evidence of CAD. Patients with:

    1. with myocarditis, cardiomyopathies, and pulmonary embolism
    2. previously diagnosed cases of CAD or on medications such as antiplatelets and statins; and
    3. with chronic kidney disease, liver failure, and steroids were excluded from the study.

Once admitted into the hospital, patients who satisfied the entry criteria for the age group and occupation were selected. Demographic factors such as age, gender, address, socioeconomic factors such as income, marital history, religion were noted. Risk factor profiles such as the presence of smoking, diabetes, hypertension, physical activity, family history of CAD, and average hours of driving were all recorded. Clinical presentation to hospital, the primary method of management (thrombolysis in STEMI patients), course in hospital, and echo on admission were also documented. Total cholesterol and triglycerides (TGs) were estimated using commercially available kits (Accurex Biomedical Pvt. Ltd., Mumbai, Maharashtra, India). Measurement of direct Low-Density Lipoprotein-cholesterol (LDL-C) was done by enzymatic homogeneous colorimetric assay using Cobas Gen3. C502 analyzer.

Body mass was measured using a portable electronic scale to the nearest 0.1 kg. Height was measured to the nearest 0.1 cm using a portable wall-mounted stadiometer. Waist (just above the iliac crest) and hip (the widest part of the hips at the middle of the pelvis) circumferences were measured to the nearest 0.1 cm. Body mass index (BMI) was calculated as body weight (kg) divided by height squared (m). Coronary angiographic profile and mode of intervention (if any) were all documented.

Statistical methods

The qualitative data were summarized by count and percentage, while quantitative data were tabulated by descriptive statistics such as mean, median, standard deviation, interquartile range, minimum, and maximum. The data were analyzed using R statistical analysis and computing language version 3.5.1 (R core team, 2018), which is released under the GNU General Public License, version 2, published by the Free Software Foundation. The “P” value was derived by Chi-square calculator with Yates correction and value of <0.001 was considered statistically significant.

  Results Top

The PCAD registry has 3450 patients so far, of which 755 (21.88%) were drivers by profession and hence included in the analysis.

Demographic characteristics

The average age of the group was 33.10 years Of which 294 (38.94%) were aged 36–40 years, 275 (36.4%) were aged 31–35 years, 149 (19.7%) were aged 26–30 years and only 37 (4.9%) were below 25 years [Figure 1].
Figure 1: Age distribution of patients in the study

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Almost all 754 (99.8%) were males, of which 323 (42.78%) smoked. The group had 83 (10.95%) diabetics and 71 (9.4%) hypertensives. Around 99 (13.11%) had a family history of CAD. The majority of them 440 (58.27%) were urban drivers (Bangalore city) with average driving of 10 h/day. The group had 25 (3.31%) graduates, 90 (11.9%) were educated up to 12th STD, 288 (38.14%) up to 10 STD, and 34 (4.5%) of them did not receive any formal education. The group had 647 (85.69%) Hindus. Only 30 (3.97%) patients were vegetarians.

Risk factor characteristics

Physical parameters showed that 254 patients (33.66%) had normal BMI, whereas 228 patients (30.19%) had high BMI (181 overweight, 47 obese), 254 patients (33.75%) were overweight according to the revised BMI classification for South Asian Indians. Going by waist-hip ratio definition, 539 patients (71.41%) had abdominal obesity [Table 1]. Almost all reported a sedentary lifestyle. Mean total cholesterol of the entire study population was 166.956 ± 47.11, LDL was 117.75 ± 84.81 mg/dl, HDL was 32.376 ± 9.64, TG was 194.166 ± 87.11. Among lipid parameters, 49 (6.4%) had high total cholesterol, 508 (67%) had low HDL, 88 (11.65%) had high LDL cholesterol, and 222 patients (29.4%) had high triglycerides [Figure 2].
Table 1: Risk factor profile of patients

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Figure 2: Distribution of conventional lipid parameters in the study group. HDL: High Density Lipoprotein, LDL: Low Density Lipoprotein

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Clinical and angiographic characteristics

ST-elevation myocardial infarction (STEMI) was the most common presentation in 415 (54.96%) patients and unstable angina/Non-ST elevation myocardial infarction (MI) was seen in 102 patients (13.50%). Furthermore, 195 patients (25.82%) had a delayed STEMI presentation (Evolved MI), 19 patients (2.51%) had spontaneous resolution of MI, and 6 (0.8%) patients presented with chronic stable angina.

In the group, 634 of 755 (83.9%) patients underwent coronary angiogram. Of which 257 (40.54%) patients had recanalized coronaries, 217 (34.22%) had obstructive CAD, 93 (14.67%) had nonobstructive CAD, 43 (6.78%) had thrombotic lesions, and 24 patients (3.78%) had normal coronaries. Left ventricular (LV) ejection fraction showed normal systolic function (>55%) in 333 patients (44.10%), mild LV systolic dysfunction (45%–54%) in 200 (26.5%) patients, moderate LV dysfunction (30%–45%) in 130 (17.2%) patients, while it was severe LV dysfunction (<30%) in 92 (11.92%) patients.

Of 755 (66.88%) patients, 505 were continued on optimal medical therapy, 217 (28.71%) patients underwent revascularization (211 PTCA, 6 CABG). Twenty-eight (3.71%) patients received triple antithrombotic therapy for predominant thrombotic lesions and were advised to repeat angiogram on follow-up. Eight (1.05%) patients underwent intracoronary thrombolysis with tenecteplase/urokinase. Among the group, 12 patients went into cardiogenic shock due to severe pump failure and died.

Further analysis of smokers versus non-smokers showed that a history of diabetes hypertension, abnormal BMI, and the presence of atherosclerotic obstructive CAD was statistically significant (P < 0.001) in smokers [Table 2]. P < 0.001 was considered significant.
Table 2: Subgroup analysis of smokers versus nonsmokers

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  Discussion Top

There are two important aspects to be considered among drivers. One is the occupational hazard and second, the impact of air pollution over and above the conventional CV risks.

Evidence for occupational hazard

Drivers are commonly exposed to many unhealthy working conditions such as long working hours, irregular shift work times, sleep disturbances, and stressful conditions.[7],[8],[9],[10],[11] They are classified as a high-risk group for work-related stress.[16] Many studies have confirmed links between occupational stress, hypertension, and heart diseases.[17],[18] Most patients in our group reported occupational stress, with average driving hours of 10 h per day, which was more than the usual prescribed by International Labour organization in their Hours of Work and Rest Periods (Road Transport) Recommendation, 1979 and also the Motor transport workers act of 1961 of the Indian government.[23] Furthermore, prolonged sitting and physical inactivity can cause hypertension, diabetes mellitus, dyslipidemia, and obesity.[12],[13],[14],[15] An abnormal BMI was noted in 63.8% of patients and almost 71.4% satisfied the criteria for abdominal obesity. Almost all the patients reported a sedentary lifestyle. The predominant form of dyslipidemia observed was low HDL cholesterol in 67% and high triglycerides in 29.4%, which is more common in the population presenting with PCAD more so, Indians with the exception of LDL which was increased only in 11.6% in our group.[24],[25]

Evidence for air pollution

Drivers also face harmful exposure to environmental pollution.[10],[11] Several studies have shown that high concentrations of fine PM and traffic-related air pollution in metropolitan cities are associated with hypertension, diabetes, and acceleration of atherosclerosis, which predispose to CV diseases.[10],[26],[27],[28],[29]

We further classified the study group into smokers and nonsmokers. It is well known that smoking is a major CV risk factor for CAD in the young, more so in Indians, and was also seen in 42.7% of patients in our group.[30],[31] We hypothesized that this classification would neutralize the effect of smoking and help in the analysis of data pertaining only to air pollution in the nonsmoker group. The other conventional risk factors such as diabetes, hypertension, obesity, dyslipidemia and family history of CAD were compared between these two groups. The presence of hypertension, diabetes, and abnormal BMI was statistically significant (P < 0.001) among smokers, indicating that air pollution was probably the major underlying risk factor in nonsmokers. Family history of CAD and Low HDL levels were equally comparable in both groups, with air pollution acting as an additional driver over and above the conventional risk factors. Some authors noted that even short-term exposure to PM 2.5 may trigger acute coronary events such as STEMI but not non-STEMI.[32],[33],[34] Similar observations were noted in our group where presentation to hospital as STEMI or evolved MI (delayed presentation of STEMI) was seen in 80.7%, and was also statistically significant in the nonsmoker group. Only 13.5% presented with non-STEMI/UA. A small number of patients presented with chronic stable angina (0.8%).

In the group, 40.5% had recanalized coronaries (post thrombolysis), 6.7% had thrombotic lesions indicating an overall hypercoagulable state due to smoking and air pollution. However, atherosclerotic obstructive CAD was seen in 34.2% and was statistically significant in the smoker's group. This observation could be because the smokers subgroup had more conventional risk factors. Most patients (70.5%) had either normal or mild LV dysfunction at discharge. Similar to other studies on patients with premature CAD.[35],[36]

Limitations of the study

  1. Actual occupational stress assessment using stress questionnaire was not done; however, the same was inferred from average hours of driving/day
  2. Number of years of driving was not documented
  3. The actual air pollution risk could not be ascertained directly; however, indirect evidence was obtained after excluding smokers by doing a subgroup analysis.

  Conclusion Top

Asian Indians have the highest risk of PCAD. A cause of concern in developing countries like India is the incomplete detection, treatment, and control of CAD risk factors. Adequate measures have to be taken by policymakers to reduce air pollution and its ill effects. Screening for CV risk factors and proper education of drivers regarding their occupational risks is important. Furthermore, to ensure strict enforcement of labor laws so that the work stress can be significantly reduced, thereby decreasing CV risk.


We would like to thank Research Coordinator, Mrs. Rani B J, and Research Assistant Mr. Prateesh, for technical help.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

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