04/11/2011
Accidents Waiting To Happen
Latest research shows that overworked and tired truck drivers, especially those who are overweight, have an increased risk of having a sleep-related road accident.
The research findings from the Brain Function Research Unit at the University of the Witwatersrand and a Canadian sleep disorders laboratory was compiled from questionnaire-based interviews with 102 long-haul truck drivers across South Africa. The problem appears global - evidence suggests that many long-haul drivers do not get sufficient sleep to maintain alertness. About 13% of Australian truck drivers obtain less than four hours of sleep per day, with one third working in excess of 72 hours per week. In South Africa, almost one-third reported sleeping less than 4 hours per day. It is widely accepted that both fatigue and sleep deprivation are major contributors to truck accidents. According to the report by Maldonado and her colleagues, published in the South African Journal of Science, police records for two major roads in South Africa show that falling asleep at the wheel contributed to a quarter or more road accidents involving heavy vehicles.
But why do drivers fall asleep?
According to the survey, three quarters of truck drivers reported being tired on the job due to long working hours, working approximately 93 hours a week, with half of them getting less than 5 hours of sleep per day. The South African Labour Relations Act (currently being revised by the National Department of Transport) restricts working to 71 hours per week, in this type of work, including overtime. These restrictions cannot be enforced and drivers are under pressure to supplement their income and to meet company expectations.
For those drivers who do manage to get some sleep in their truck, Maldonado and her team reported that their sleep was interrupted mostly by noise as well as light, outside activity and extremes of heat or cold. Almost eight out of 10 of the drivers surveyed complained of interrupted sleep; in this case poor sleep is associated with up to 62% of incidents where drivers nodded off at the wheel, increasing the risk of causing a road accident.
But there is more to it.
The research team showed that the problem is compounded by sleep disorders such as apnoea and snoring, which show an unusually high prevalence in long-haul truck drivers. These disorders have been shown to increase sleepiness and reduce attention. Drivers who admit to snoring or experience signs indicative of sleep apnoea, or other sleep complaints, show a two-fold increase in sleep-related road accidents compared with drivers without sleep disorders. Sleep apnoea is characterised by loud snoring and respiratory pauses. Sleep apnoeics tend to stop breathing while asleep, wake up gasping for breath and then start snoring again once they return to sleep. When sufferers stop breathing their brain is forced to wake them up to start breathing again. In cases of severe sleep apnoea, this can occur up to 600 times per night, meaning that they also are waking up that many times in a night.
Drivers who snore or show signs indicative of sleep apnoea are also more likely to be overweight. Obese drivers who snore or experience excessive daytime sleepiness fall asleep at the wheel more often and are twice as likely to have an accident compared to those who do not snore. There also appears to be a correlation between severe sleep apnoea and heart failure and the likelihood of getting strokes or hypertension.
The human body follows an internally generated sleep-wake cycle governed predominantly by the production of a hormone known as melatonin. Melatonin production during darkness stimulates sleep, while low levels of melatonin, usually in periods of light exposure, signals wakefulness. Almost all the drivers interviewed stated that they started driving between 1 am and 8 am, a period when melatonin levels are high and the stimulus for sleep is also high.
The highest incidence of sleep-related vehicle accidents occurs between midnight and 6 am, coinciding with the circadian dip in alertness. Regularising sleep-wake cycles can improve alertness and reduces sleepiness.
Enforcing the regulations
According to Maldonado and team, South African truck drivers are at risk of causing sleep-related accidents as much as other truck drivers in more affluent countries, except that truck drivers in South Africa also have to contend with unsafe social circumstances and poor conditions at truck stops. The study recommends shortening driving time and working hours, increasing time for sleep and relaxation, rescheduling driving trips towards regular work hours, improving sleep conditions for truck drivers, and also treating sleep disorders and obesity where they occur.
Driving while deprived of sleep poses a risk to all road users. Regulations should be enforced at the company level.
