This is the most recent study of its kind that we know of in the UK; similar studies have been conducted in the USA, Brazil, Australia, France, New Zealand and Greece. Previous UK studies have been conducted by a CPAP company, creating a conflict of interest (Moylan 2005) and a survey in which investigators classified BMI categories without taking measurements (Maycock 1995).
A main aim of the current work was to identify what percentage of HGV drivers in a sample study population have suspected OSA and to see how they differed to the rest of the study population. 9.46% were identified as having suspected OSA. The suspected OSA cases are much than the estimated 4% prevalence in the general male population (Young et al. 1997), although less than in a Swedish and Australian studies using overnight PSG in HGV drivers at 17% and 15.8% respectively (Carter et al. 2003, Howard et al. 2004).The main basis for suspicion of OSA in the current study was reports of witnessed apnoeas by bed partners; however, 20.27% of drivers did not have a bed partner so cases of suspected OSA maybe under reported. 2.70% of the total sample reported prior diagnosis of OSA, as they were all currently employed as
professional HGV drivers and did not show EDS it is assumed they were all successfully treated.
Those with suspected OSA were significantly more likely to be suffering from EDS than the remainder of the study population, the odds of having EDS being 14.78 times higher for this subgroup than the study population as a whole. Elevated EDS puts a person at greater risk of falling asleep at the wheel and suggests they should ideally be tested for OSA. Of those participants with suspected OSA, 35.7% were younger than 45 years old so will not yet require a medical examination to retain their licence. The remained were aged between 45 and 65 years so were subject to medical examinations every 5 years. It is possible that the current required medicals are not picking up all cases of OSA.
One of the key risk factors for OSA is obesity, 88.5% of the study population were found to be either over-weight or obese, this is comparable with Gurubhagavatula et al. (2004) a USA study which found a prevalence of 88% overweight or obese HGV drivers. Additionally, overweight men have been found likely to underestimate their weight (Kuchler et al. 2003) as a result it is probable that the BMI maybe artificially lower than it would have been if all participants consented to anthropometric measurements being taken.
Overall it has been found that there is a higher prevalence of risk factors and symptoms of OSA in a sample of HGV drives on UK roads, than in the general population. In comparison to the general public population statistics this sample of HGV drivers demonstrate a male dominated environment (Office for National Statistics 2007) with higher prevalence of obesity (NHS Information Centre 2006) and greater average neck circumference (Martin et al. 1997). EDS is a common symptom of OSA and although the average ESS for the HGV drivers surveyed was not at a critical level it is 2.1 higher than a sample of the general public (Johns et al 1997). Another common symptom of OSA is snoring and again this is more prevalent in HGV drivers than the general population (Ohayon et al. 1997), suggesting that OSA may be more prevalent
reports of witnessed apnoeas, which were reported almost twice as much as in a sample of the general population (Ohayon et al. 1997). The HGV driver population appears to be at greater risk of OSA than the general population.
From the survey completed none of the factors assessed were significantly associated with reports of drivers having falling asleep at the wheel. Smokers were significantly more likely to have an ESS ≥ 12 than non smokers, but no other factors were significantly associated with EDS. It is not possible to know if one causes the other as smoking may result in greater daytime sleepiness or it is possible that individuals may decide to smoke because they are sleepy and nicotine, as a stimulant, increases their alertness.
Participants in the current study had an average age of 47.3 y which is older than found in similar studies in other countries where average age in late 30s is more common (Stoohs et al. 1995, Philip et al. 2002, Gurubhagavatula et al. 2004, Canani et al. 2005, Tzamalouka et al. 2005, Gander et al. 2006, Hanowski et al. 2007). Having an older HGV driving population in the UK may increase the number of HGV drivers suffering from OSA as the condition is more prevalent in those aged over 40.
The majority of participants were driving for the maximum time period allowed under EU law before taking a break. These truck drivers appeared generally happy with the requirements of the job and the majority were not unwilling to drive these hours, 25.68% even said they would be happy to drive for longer before taking a break. The average driving week was reported as 43.07 hours which is less than the 56 hours per week allowed by law (EU law).
In comparing self reported sleep time on work nights and non work nights almost 60% reported a difference. However, approximately 40% of those losing sleep only have an hour or less difference in sleep time between work and non work nights, so this is likely to have minimal impact. More worryingly approximately 13% those reporting sleep loss on work nights recorded a difference of 4 to 6 hours; this is a large difference in sleep time and may result in impairment at work.
HGV drivers cover approximately 81 489 miles more per year than the average car driver (comparing millage reports in the current study and car driving mileage (Department for Transport 2009). Additionally they appear to be at greater risk of OSA (as suggested by prevalence of symptoms and risk factors in this sample) than the general public. It is therefore very important that HGV drivers are able to recognise sleepiness as a hazard to driving and be able to take effective counter measures. The majority of the HGV drivers in this sample reported having felt sleepy whilst driving and the majority recognised that driving whilst drowsy could affect their ability to drive safely. However, 12.8% felt driving whilst drowsy did not affect their ability to drive safely and this was despite 36.8% of these drivers reporting that they had fallen asleep at the wheel. It is possible that they have this response because they have fallen asleep while driving in the past and there have been no consequences.
18.9% of drivers admitted to having fallen asleep at the wheel in the past, this is a lower percentage than in some other studies which have found 22% (Canani et al. 2005), 23% (Tzamalouka et al. 2005), and 47.1% (McCartt et al. 2000). However, admitting to falling asleep at the wheel is admitting to dangerous driving and even though the questionnaire is anonymous some drivers may have been unwilling to admit if they had fallen asleep at the wheel.
This survey has shown that prevalence of undiagnosed OSA in a sample of UK HGV drivers is potentially higher than in the general population. It suggests that there are HGV drivers who are driving long distances for prolonged periods of time whilst having undiagnosed OSA. This will predispose them to EDS which may increase the chance of them having an accident. Offering screening and treatment is likely not to be enough, the industry as a whole needs to show acceptance towards treated OSA drivers or people will not be willing to come forward and be tested. In order for the industry to be accepting it is important to know that the treatment is effective and that driving performance is equivalent to healthy drivers both at the onset of treatment and in the long term.
2008). However, as we have found, drivers who are subject to medicals are still falling into the high risk group of suspected OSA. It is unclear if this is because GPs carrying out current medicals are not recognising the symptoms of OSA or that the frequency of medicals at five years is not sufficient.
Another problem is even if drivers are diagnosed with OSA it can be difficult to get them to accept and regularly use treatment. One USA study surveyed 456 HGV drivers and identified 53 as showing signs of OSA, these were all invited for PSG but only 20 turned up to be tested. All 20 had OSA but in a follow up only 1 patient reported using their treatment (Parks et al 2009). There is a problem with adherence to CPAP treatment for all OSA patients (Weaver et al. 2008) but the issue of unwillingness to seek help may be exacerbated by fear of losing their driving licence and job.
2.4.1 Limitations
The sample size of 148 is adequate for the purpose of this study, however there are 528, 000 licensed heavy goods vehicles in the UK, so to get a more detailed picture of the HGV drivers in the UK, a larger sample size would be required. In order to achieve this, more than one survey site would be needed. The current study was limited to one local survey site and data was collected over several weeks. It was noted that by the end of the data collection investigators were encountering customers of the café who had already completed the survey on a previous occasion. Encompassing more HGV stops would allow a larger sample size to be collected; unfortunately the current study did not have the resources to do this. Another way to reach a larger potential study population would be to conduct a postal survey. However, this would mean that anthropometric measurements would not be taken by the investigator and results would be reliant on accurate reports from participants.
The most feasible way to get contact details of large numbers of HGV drivers would be through large national employers. However, even if a questionnaire remained anonymous people may be unwilling to answer questions such as “Have you fallen asleep at the wheel?” honestly if they think that their employer may find out. A postal survey would allow participants to fill the questionnaire in at a time appropriate to them and would not impose on their meal time. Conducting research in a café may
also bias the type of person who fills in the survey as by nature of a truck stop anyone in it has “stopped” driving, those wishing to keep going will not be represented. Also any drivers who had brought their own meal may have been eating in their HGV and will not have been represented.
The questionnaire was designed to take 5 minutes to complete in the hope that a large number of people would complete it. More accurate identification of suspected OSA could have been obtained by using additional questionnaires specifically designed for diagnosis of OSA. However, because drivers were there to eat, the focus was on keeping the survey short. An area of questioning not included was the pattern of working hours; it is not possible to tell from this survey if drivers worked at night or during the day. This may have an effect as sleep-related crashes are more likely to occur in the early hours of the morning than at any other time (Horne et al. 1995). PSG recordings were not carried out so a conclusive diagnosis of how many drivers had OSA is not known. Due to time and cost this was not feasible to complete.
No questions were asked about drinks containing small amounts of caffeine such as tea and cola. In small quantities the amount of caffeine received in these drinks is not enough to promote alertness. It would have been useful to know if they had been consumed in quantities large enough that may have impacted alertness.
The ethnicity and country the driving licence was not recorded. UK drivers are subject to medical checks from the age of 45 but foreign drivers may not be. This meant it was not possible to distinguish if the OSA with suspected OSA had received a medical check or not.