According to a report published in 2018, about 151,417 deaths occurred in road traffic accidents [1]. Difficult driving conditions arising because of time constraint, long shifts, distant travels, and bad weather which increases the risky driving by heavy vehicle drivers leading to road accidents [2,3]. PHVDs are more prone to lifestyle disorders like diabetes and obesity [4]. Neurologic impairment like cognitive impairment, inability to balance, motor control and vision impairment adds to the morbidity and mortality in drivers [2,3]. Majority of the drivers with peripheral neuropathy involved in accident attribute their peripheral neuropathy as the cause of accident [5]. Repetitive or sustained flexion of the wrist or contraction of the muscles whose tendons pass through the carpal tunnel, especially when doing forceful work has been found to cause inflammation of tendons which can alter the space or pressure within the carpal tunnel, thus compressing the median nerve [6,7]. There is increased risk of Carpal Tunnel Syndrome (CTS) among drivers on long journeys and truck drivers [8,9]. Vibration transmitted from steering wheel and pedals called Hand Transmitted Vibration (HTV) and FTV [10] may lead to finger blanching [11], CTS [7] and white feet syndrome [9] in drivers.
Since professional drivers are responsible for driving commercial vehicles, they are viable for economic growth and completing the chain of production to the consumption. For a developing country and fast growing economy like India, the research on occupational hazard of driving on the nerve conduction in professional drivers is scanty. Singh D et al., in their study on median neuropathy among various professionals found 47% subjects with peripheral neuropathy. However, among them they found tailors to be maximally affected and drivers were moderately affected [12]. Afsar S et al., in their study on Turkish taxi drivers found peripheral neuropathy amongst 82.5% drivers [13].
The purpose of this study was to find early the neurological component of occupational health hazard of driving like peripheral neuropathies which is noticed at a late stage when considerable amount of nerve damage has occurred. This research is expected to contribute for improved and early preventive measures, better work schedules and improvements in ergonomics of truck designing.
Materials and Methods
The present study was a cross-sectional study in which 180 subjects (90 subjects were PHVDs and 90 were non-drivers) were included and study was completed over a span of two years from November 2014 to December 2016. The study was approved by the College Human Institutional Ethical Committee (JNMCH dop: 11/14). The NCS, to estimate the motor and sensory NCV, was performed in the Neurophysiology Laboratory in the Department of Physiology, JN Medical College. For differentiating between cases and controls, subjects were grouped as controls (non-drivers) if they don’t hold a valid motor driving license. They were largely medical college office staff not holding valid light/heavy motor vehicle license for more than five years.
Participants who were continuously in the profession of driving heavy vehicles like trucks at least for the last five years were considered to be PHVDs [14-17]. PHVDs with intercity/interstate booking for more than 20 days every month for last six months in booking register were included in the study. They were chosen by simple randomised sampling from the transport offices located in the city.
A total of 210 professional drivers were interviewed telephonically or face-to-face and asked to participate in the study. A total of 180 drivers were ready to participate in the study and 30 drivers refused to participate citing busy schedule, apprehension or not interested in study. Selection of the eligible participant was done after taking history.
Inclusion Criteria
Control
Willingness (informed consent).
Age ≥30 years.
Normal and healthy adults male.
Do not hold valid light/heavy motor vehicle license.
Case
Age ≥30 years.
Willingness (informed consent).
Adult males in profession of truck driving at least for last consecutive five years.
Driving trucks intercity/interstate.
Truck driving for more than 20 days every month at least for last six months.
Exclusion Criteria
Diabetes mellitus.
Renal failure.
Neuropathies associated with toxic agents e.g., metal or drugs.
Neuropathies associated with malnutrition, alcoholic hepatitis or medication.
Skin lesion or swelling that would interfere with nerve conduction study.
Previous trauma to the study site.
Hormone replacement therapy.
Other serious illness (for example, cardiac failure or HIV infection), a family history of peripheral neuropathy.
Subjects having any sign or symptom of sensory or motor peripheral neuropathy based on interview and clinical examination.
After screening of 180 drivers on the basis of predefined inclusion and exclusion criteria 130 drivers were shortlisted in the PHVD category. All the shortlisted participants were asked to undergo neurological clinical examination and nerve conduction study in the neurophysiology lab. Twenty eight drivers were further excluded as they were found unsuitable after clinical examination or they opted out due to apprehensions about the test, not any more interested in the study, or non-availability of dates, 12 drivers did not turn up on their scheduled date. Due to the busy schedule of the drivers and no financial support only nerve conduction study was done. A total of 180 subjects (90 cases and 90 controls) participated in the study. They were explained about the purpose and procedure of the study and written informed consent in compliance with requirements of the Helsinki Declaration taken. No monetary benefits were offered and the participation was purely voluntary.
Nerve Conduction Study
Participants (drivers and non-drivers) were explained about nerve conduction study and it’s the non-invasive procedure to conduct the test. The equipment used for nerve conduction study was Medicaid System’s EMG/NCV equipment with neuroperfect software.
Nerve conduction studies were performed on both the right and left side of every participant. Supramaximal stimulation was applied to obtain reliable and reproducible evoked responses in both motor and sensory nerve conduction studies. Sensory and motor latencies amplitudes and conduction velocities of the median, ulnar and common peroneal nerve were recorded [18,19].
Statistical Analysis
For data analysis and interpretation Statistical Package for the Social Sciences (SPSS) version 20 was used and values were expressed in mean and standard deviation. Student’s unpaired t-test was used to assess the significance of difference in NCS findings between the mean values of median, ulnar, common peroneal nerve. The p-value <0.001 was considered as significant.
Results
The mean age of the non-drivers was 42.4±7.5 and their BMI was 25.3±3.8. Mean age of heavy vehicle drivers was 40.2±8.30 and their BMI was 26.2±2.9 (p-value >0.05) [Table/Fig-1]. Since all the drivers were male participants we included only male non-drivers for comparison. All the participants were right hand dominant.
Demographic distribution of cases and controls.
| S. No. | Age | Non-drivers | Professional heavy vehicle drivers |
|---|
| 1 | Mean age±SD | 42.4±7.5 | 40.20±8.30 |
| 2 | 31-40 year | 48 | 53 |
| 3 | 41-50 years | 37 | 34 |
| 4 | >50 years | 5 | 3 |
| 5 | BMI (kg/mg2) | 25.3±3.8 | 26.2±2.9 |
Nerve conduction parameters of median nerve in drivers and non-drivers: In drivers there was a significant slowing in the SNCV of median nerve of both right and left side as compared to the healthy controls (non-drivers). Mean peak sensory latency was significantly prolonged in drivers in comparison to non-drivers for median nerve in right and left hand [Table/Fig-2].
Nerve conduction parameters of median nerve.
| S. No. | Nerve conduction study | Right/Left hand | Median nerve conduction parameters | p-value |
|---|
| Non-drivers (n=90) | Professional heavy motor vehicle drivers (n=90) |
|---|
| 1 | Mean Peak Sensory Latency | Right hand | 2.89±0.56 | 3.71±0.72 | <0.0001 |
| Left hand | 2.76±0.70 | 3.4±0.81 | <0.0001 |
| 2 | Mean Motor Latency | Right hand | 3.45±0.51 | 3.59±0.67 | 0.1165 |
| Left hand | 3.42±0.69 | 3.59±0.77 | 0.1206 |
| 3 | Mean MNCV(Motor Nerve Conduction Velocity) | Right hand | 53.14±4.36 | 52.55±5.04 | 0.4021 |
| Left hand | 51.13±3.80 | 52.17±3.90 | 0.0717 |
| 4 | Mean SNCV(Sensory Nerve Conduction Velocity) | Right hand | 53.66±3.60 | 51.40±3.30 | 0.0001 |
| Left hand | 53.87±3.61 | 52.51±3.78 | 0.0145 |
| 5 | Mean SNAP(Sensory Nerve Action Potential in microvolt) | Right leg | 39.12±11.7 | 38.22±12.2 | 0.6141 |
| Left leg | 40.73±12.4 | 40.34±10.8 | 0.8222 |
| 6 | CMAP(Compound Muscle Action Potential) | Right leg | 5.67±0.98 | 5.42±1.18 | 0.1238 |
| Left leg | 5.54±0.80 | 5.40±1.42 | 0.4162 |
Student’s unpaired t-test was used
Nerve conduction parameters of ulnar nerve in drivers and non-drivers: Peak sensory latencies shows significant difference in right and left hand amongst drivers but no significant difference in non-drivers [Table/Fig-3].
Nerve conduction parameters of ulnar nerve.
| S. No. | Nerve conduction study | Right/Left hand | Ulnar nerve conduction parameters | p-value |
|---|
| Non drivers (n=90) | Professional heavy vehicle drivers (n=90) |
|---|
| 1 | Mean Peak Sensory Latency | Right hand | 2.76±0.42 | 2.98±0.52 | 0.0021 |
| Left hand | 2.80±0.65 | 2.97±0.42 | 0.0386 |
| 2 | Mean Motor Latency | Right hand | 3.06±0.44 | 2.95±0.52 | 0.1273 |
| Left hand | 3.23±0.60 | 3.13±0.65 | 0.2850 |
| 3 | Mean MNCV(Motor Nerve Conduction Velocity) | Right hand | 54.67±3.50 | 53.92±3.30 | 0.1409 |
| Left hand | 54.77±3.42 | 53.9±2.89 | 0.0669 |
| 4 | Mean SNCV(Sensory Nerve Conduction Velocity) | Right hand | 54.34±4.80 | 53.78±3.80 | 0.3867 |
| Left hand | 55.72±4.60 | 54.48±3.90 | 0.0527 |
| 5 | Mean SNAP(Sensory Nerve Action Potential) in microvolt | Right leg | 35.4±10.6 | 34.2±11.2 | 0.4613 |
| Left leg | 34.2±9.8 | 33.8±10.7 | 0.7940 |
| 6 | CMAP(Compound Muscle Action Potential) | Right leg | 6.5±1.3 | 6.2±1.6 | 0.1692 |
| Left leg | 6.8±1.5 | 6.6±1.48 | 0.3691 |
Student’s unpaired t-test was used
Nerve conduction parameters of common peroneal nerve in drivers and non-drivers: Sensory latency was significantly prolonged in drivers in comparison to non-drivers for sural nerve in right and left limb [Table/Fig-4].
Nerve conduction parameters of common peroneal nerve.
| S. No. | Nerve conduction study | Right/Left lower limb | Common peroneal nerve conduction parameters | p-value |
|---|
| Non-drivers (n=90) | Professional heavy vehicle drivers (n=90) |
|---|
| 1 | Mean Peak Sensory Latency | Right leg | 2.78±0.54 | 3.05±0.55 | 0.0011 |
| Left leg | 2.69±0.40 | 2.92±0.45 | 0.0004 |
| 2 | Mean Motor Latency | Right leg | 4.55±0.71 | 4.77±0.81 | 0.0557 |
| Left leg | 4.50±0.69 | 4.67±0.86 | 0.1453 |
| 3 | Mean MNCV(Motor Nerve Conduction Velocity) | Right leg | 50.20±4.49 | 49.45±5.03 | 0.2927 |
| Left leg | 49.92±5.11 | 49.47±5.15 | 0.5570 |
| 4 | Mean SNCV(Sensory Nerve Conduction Velocity) | Right leg | 48.95±4.39 | 48.06±2.48 | 0.0958 |
| Left leg | 48.47±3.56 | 47.71±2.98 | 0.1222 |
| 5 | Mean SNAP(Sensory Nerve Action Potential) in microvolt | Right leg | 4.48±0.80 | 4.71±1.30 | 0.1546 |
| Left leg | 4.27±1.33 | 4.65±1.27 | 0.0515 |
| 6 | CMAP (Compound Muscle Action Potential) | Right leg | 4.94±1.83 | 4.89±1.80 | 0.8536 |
| Left leg | 4.88±1.67 | 4.78±1.74 | 0.6945 |
Student’s unpaired t-test was used
Comparison of median nerve conduction parameters in right and left hand: In median nerve there was significant difference in peak sensory latencies of right and left hand in drivers but the peak sensory latencies does not show significant difference in right and left hand of non-drivers [Table/Fig-5].
Comparison of nerve conduction parameters in right and left median nerve.
| S. No. | Nerve conduction parameters | Right hand | Left hand | p-value |
|---|
| 1 | Mean peak Sensory Latency in Non-drivers (n=90) | 2.89±0.56 | 2.76±0.70 | 0.1706 |
| Mean peak Sensory Latency in professional Heavy Vehicle Drivers (n=90) | 3.71±0.72 | 3.4±0.81 | 0.0073 |
| 2 | Mean Motor Latency in Non-drivers (n=90) | 3.45±0.51 | 3.42±0.69 | 0.9721 |
| Mean Motor Latency in professional Heavy Vehicle Drivers (n=90) | 3.59±0.67 | 3.59±0.77 | 0.8679 |
| 3 | Mean MNCV(Motor Nerve Conduction Velocity) in Non-drivers (n=90) | 53.14±4.36 | 51.13±3.80 | 0.7286 |
| Mean MNCV(Motor Nerve Conduction Velocity) in professional Heavy Vehicle Drivers (n=90) | 52.55±5.04 | 52.17±3.90 | 0.9525 |
| 4 | Mean SNCV(Sensory Nerve Conduction Velocity) in Non-drivers (n=90) | 53.66±3.60 | 53.87±3.61 | 0.9645 |
| Mean SNCV(Sensory Nerve Conduction Velocity) in professional Heavy Vehicle Drivers (n=90) | 51.40±3.30 | 52.51±3.78 | 0.8252 |
| 5 | Mean SNAP(Sensory Nerve Action Potential) in microvolt in Non-drivers (n=90) | 39.12±11.70 | 40.73±12.40 | 0.3715 |
| Mean SNAP(Sensory Nerve Action Potential) in microvolt in professional Heavy Vehicle Drivers (n=90) | 38.22±12.20 | 40.34±10.8 | 0.2187 |
| 6 | CMAP (Compound Muscle Action Potential) in Non-drivers (n=90) | 5.67±0.98 | 5.54±0.80 | 0.3309 |
| CMAP (Compound Muscle Action Potential) in professional Heavy Vehicle Drivers (n=90) | 5.42±1.18 | 5.40±1.42 | 0.9183 |
Student’s unpaired t-test was used
Comparison of ulnar nerve conduction parameters in right and left hand: In ulnar nerve there was no significant difference in the nerve conduction study parameters of right and left hand in drivers and non-drivers [Table/Fig-6].
Comparison of nerve conduction parameters in right and left ulnar nerve.
| S. No. | Nerve conduction parameters | Right hand | Left hand | p-value |
|---|
| 1 | Mean peak Sensory Latency in Non-drivers (n=90) | 2.76±0.42 | 2.80±0.65 | 0.9588 |
| Mean peak Sensory Latency in professional Heavy Vehicle Drivers (n=90) | 2.98±0.52 | 2.97±0.42 | 0.9881 |
| 2 | Mean Motor Latency in Non-drivers (n=90) | 3.06±0.44 | 3.23±0.60 | 0.8195 |
| Mean Motor Latency in professional Heavy Vehicle Drivers (n=90) | 2.95±0.52 | 3.13±0.65 | 0.8290 |
| 3 | Mean MNCV(Motor Nerve Conduction Velocity) in Non-drivers (n=90) | 54.67±3.50 | 54.77±3.42 | 0.8465 |
| Mean MNCV(Motor Nerve Conduction Velocity) in professional Heavy Vehicle Drivers (n=90) | 53.92±3.30 | 53.90±2.89 | 0.9655 |
| 4 | Mean SNCV(Sensory Nerve Conduction Velocity) in Non-drivers (n=90) | 54.34±4.80 | 55.72±4.60 | 0.0505 |
| Mean SNCV(Sensory Nerve Conduction Velocity) in professional Heavy Vehicle Drivers (n=90) | 53.78±3.80 | 54.48±3.90 | 0.2242 |
| 5 | Mean SNAP(Sensory Nerve Action Potential) in microvolt Non-drivers (n=90) | 35.4±10.60 | 34.2±9.8 | 0.4313 |
| Mean SNAP(Sensory Nerve Action Potential) in microvolt in professional Heavy Vehicle Drivers (n=90) | 34.20±11.20 | 33.80±10.70 | 0.8068 |
| 6 | CMAP (Compound Muscle Action Potential) in Non-drivers (n=90) | 6.5±1.30 | 6.8±1.50 | 0.1534 |
| CMAP (Compound Muscle Action Potential) in professional Heavy Vehicle Drivers (n=90) | 6.20±1.6 | 6.6±1.48 | 0.0834 |
Student’s unpaired t-test was used
Comparison of common peroneal nerve conduction study in right and left leg: In common peroneal nerve there was no significant difference in the nerve conduction study parameters of right and left common peroneal nerve in drivers and non-drivers [Table/Fig-7].
Comparison of nerve conduction parameters in right and left common peroneal nerve.
| S. No. | Nerve conduction parameters | Right leg | Left leg | p-value |
|---|
| 1 | Mean peak Sensory Latency in Non-drivers (n=90) | 2.78±0.54 | 2.69±0.40 | 0.8936 |
| Mean peak Sensory Latency in professional Heavy Vehicle Drivers (n=90) | 3.05±0.55 | 2.92±0.45 | 0.8551 |
| 2 | Mean Motor Latency in Non-drivers (n=90) | 4.55±0.71 | 4.50±0.69 | 0.6324 |
| Mean Motor Latency in professional Heavy Vehicle Drivers (n=90) | 4.77±0.81 | 4.67±0.86 | 0.4230 |
| 3 | Mean MNCV(Motor Nerve Conduction Velocity) in Non-drivers (n=90) | 50.20±4.49 | 49.92±5.11 | 0.9672 |
| Mean MNCV(Motor Nerve Conduction Velocity) in professional Heavy Vehicle Drivers (n=90) | 49.45±5.03 | 49.47±5.15 | 0.9978 |
| 4 | Mean SNCV(Sensory Nerve Conduction Velocity) in Non-drivers (n=90) | 48.95±4.39 | 48.47±3.56 | 0.4215 |
| Mean SNCV(Sensory Nerve Conduction Velocity) in professional Heavy Vehicle Drivers (n=90) | 48.06±2.48 | 47.71±2.98 | 0.3929 |
| 5 | Mean SNAP(Sensory Nerve Action Potential) in microvolt in Non-drivers (n=90) | 4.48±0.80 | 4.27±1.33 | 0.2009 |
| Mean SNAP(Sensory Nerve Action Potential) in microvolt in professional Heavy Vehicle Drivers (n=90) | 4.71±1.30 | 4.65±1.27 | 0.7545 |
| 6 | CMAP (Compound Muscle Action Potential) in Non-drivers (n=90) | 4.94±1.83 | 4.88±1.67 | 0.8185 |
| CMAP (Compound Muscle Action Potential) in professional Heavy Vehicle Drivers (n=90) | 4.89±1.80 | 4.78±1.74 | 0.6773 |
Student’s unpaired t-test was used
Discussion
Nerve conduction studies are considered to be the most sensitive, reliable, and non-invasive method to test the condition of nerves. Exposure to vibration, mechanical pressure, repeated movements at the wrist may have been associated with an increased risk of developing CTS [20,21]. The individual variation in risk factors, varying workplace exposure and duration of forceful exertion has a greater risk of CTS than anthropometry [2]. On exposure to vibration, structural signs seen are demyelination of the nerve fiber (indicating that the schwann cells are soon affected by the vibration exposure), and these abnormal changes are more pronounced than the loss of axons [22]. Signs of proliferation of non-neuronal cells such as schwann cells after vibration exposure have been detected [23]. Due to repeated nerve compression and traction the peripheral nerves while passing through anatomical compartment become too tight leading to disorders of the intraneural microcirculation, lesions in the myelin sheath and the axon [24]. There is also the accumulation of inflammatory proteins, cytokines which are released leading to a vicious circle [25].
Forearm of the truck drivers while driving, rest over steering wheel which may further increase the pressure on nerves leading to peripheral neuropathy. Changes in median nerve in the CTS are likely to be even more severe and further trauma may be added to the nerve from repetitive motions and strenuous manual work as the nerve lies closer to the vibrating source [26-28].
In the present study nerve conduction study on PHVDs and non-drivers was conducted and it was found that long-haul professional drivers, driving heavy vehicles showed conduction slowing and increased latency in the median nerve of both right (steering wheel using) hand and left (gear changing) hand in comparison to non-drivers. There was significant slowing of SNCV of median nerve in both hands, sensory latency was also significantly prolonged in PHVD in comparison to non-drivers for median nerve in right and left hand. Present study findings were similar to the findings of Singh D et al., who in their nerve conduction study on various professionals found significant number of drivers with CTS [13].
Amatya M and Khanal B in their study on taxi drivers concluded median and ulnar involvement in taxi drivers who were regularly driving for last six months [9]. In present study, on ulnar nerve only sensory latency was found to be significantly prolonged which could be due to the different driving posture of taxi drivers, as taxi drivers frequently rest their right hand over the window while driving [11].
In the present study it was found that 44% of drivers and 18% of non-drivers were having asymptomatic median nerve neuropathy in comparison to Turkish drivers who found no significant difference in median nerve conduction parameters, as Turkish drivers while left side driving used to rest their left hand on window. In Indian truck drivers right side driving could be the cause that they drive by dominant (right) hand and so they don’t rest their right hand over window [12].
There was no significant slowing of motor nerve conduction studies, it may be due to the reason that sensory conduction loss occurs earlier and subjects who have developed clinical peripheral neuropathies while driving over many years were excluded based on exclusion criteria, so in present study subjects were asymptomatic for peripheral neuropathies [28]. MNCV and SNCV of ulnar nerve does not show significant difference in the nerve conduction studies. Sensory nerve conduction study of sural nerve showed significant slowing of the sensory latency in both legs. Jensen A et al., in their study amongst various type of vehicle drivers found higher incidence of CTS amongst long haul truck drivers. They concluded type of vehicle and different working conditions cause different health effects [8].
Sensory peripheral neuropathies may lead to impaired judgement of applying proper pressure over pedals for braking and accelerating. Early detection of peripheral neuropathies could prevent this impending danger and would make driving safer [22]. Though there are few studies available in this field to date, it is clear that long duration pressure with repeated movements at wrist while changing gears may lead to increased pressure on the median nerve at the carpal tunnel and sural nerve whereas ulnar nerve is less prone. Though the quality of evidence in the available literature is relatively low, it still contains numerous valuable observations and suggestions for all professionals working in this field. There is a need for further research, even in the form of preliminary or pilot studies, to assess the scope of this study in other countries. Researchers should also attempt to assess the impact of NCV on female drivers, and between age group of 18-29 years, those in remote or rural areas. In addition, because of the limited sample size, these findings may not represent the entire population. Therefore, a larger sample size might be needed so that information regarding effective therapeutic strategies can be widely disseminated among those working in this field. It is proposed that a long term cohort study should be conducted to determine progression and development of peripheral neuropathy in heavy motor vehicle drivers.
Limitation(s)
Cross-sectional design was the limitation of present study, as it cannot provide strong evidence for causality. Thus, further research should use a longitudinal design. Due to the financial constraints, busy schedule of drivers and lack of resources we are unable to do quantitative sensory testing of heavy vehicle drivers.
Conclusion(s)
Ulnar nerve and common peroneal nerve in truck drivers is relatively less affected by pressure induced peripheral neuropathy, vibration transmitted injury and injury due to repetitive movements at hands. In the Indian context, the present study is a unique, well-designed quantitative, observational study to target the occupational hazards of heavy motor vehicle driving on peripheral nerves; it will serve as guide for neurophysiologist and other healthcare workers, which can help in improving neurological health in drivers.
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