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What this paper adds
There are still few studies on the prevalence of psychoactive substance use by truck drivers.
The prevalence is higher when information is obtained by self-report in comparison to biological samples.
Individual characteristics were mainly associated with alcohol consumption while poor working conditions were mostly associated with amphetamine intake.
It is recommended that future studies use standardised measurements that allow them to be properly compared, including meta-analyses to estimate joint association measures.
Road transportation of goods drives the economic development in several countries,1 ,2 especially in those with large territories and insufficient or inadequate railroad transport. Truck drivers are the main agents in this transportation system3 and their activity has unique features regarding work organisation, such as goals and short deadlines to achieve them, and also strenuous working hours.4
These drivers are subjected to countless factors that influence their professional practice, among which the intake of psychoactive substances stands out,5 ,6 used for reducing sleepiness during the trips and increasing willingness for work and socialisation. However, the use of these substances may cause harmful effects to the individual and to society. Amphetamines, when used to aid in sleepiness reduction, may cause agitation, tachycardia, vertigo and hallucinations, besides altering the body's perceptions and reactions, thus raising the risk of traffic accidents.7–9
Despite the relevance of the subject, both socially and economically and also in the workers’ health, the currently available evidence on the use of psychoactive substances by truck drivers consists of localised studies in specific contexts of each place studied. Considering that the analysis of individual studies provides little knowledge for elaborating measures to address the problem, this systematic review aimed to summarise the scientific evidence on the prevalence of psychoactive substance use and the factors associated with this intake among truck drivers.
A systematic review was performed on the studies about the intake of psychoactive substances by truck drivers. Studies were selected if they were original and with quantitative results specifically on the use of psychoactive substances by truck drivers. No restrictions were made regarding language and year of publication. The recommendations of the Preferred Reporting Items of Systematic Reviews and Meta-Analyses10 were followed when applicable.
The studies were identified by consulting the databases PubMed, Scientific Electronic Library Online (SciELO), Latin American and Caribbean Health Sciences (LILACS) and Cochrane until the 30 April 2013. The PubMed search was carried out by combining the following keywords in the title or abstract: ‘truck’, “lorry’, ‘lorries’, ‘heavy vehicle’, ‘heavy transport’, ‘motorist’, ‘driver’, ‘conductor’, ‘worker’, ‘job’, ‘professional’, ‘drug’, ‘stimulant’, ‘substance’, ‘medicine’, ‘medication’, ‘psychoactive’, ‘amphetamine’, ‘cocaine’, ‘marijuana’, ‘crack’, ‘alcohol’ and ‘caffeine’ (the search strategy can be found in the online supplemental material). For the SciELO and LILACS database searches, the terms ‘truck’, ‘truck drivers’ or ‘load transport’ were used, while in the Cochrane database the studies selected included the terms ‘truck’, ‘lorry’, ‘lorries’, ‘heavy vehicle’ or ‘heavy transport’. The search strategy was based on language and syntax adequate to each database.
After the initial selection, studies whose titles clearly indicated they were not related to the subject were discarded. In a second step, the analysis of the abstracts made it possible to exclude other studies. During these steps, the review papers were kept. The remaining publications were obtained and analysed thoroughly. Moreover, their references were examined so that other papers could be located that had not been identified through the search strategy employed. After this process, the studies that fit the previously defined inclusion criteria were kept.
The whole article selection and review process was carried out independently by two researchers, who cross-checked their results in each of the steps and settled the discrepancies through consensus. A third researcher was consulted in case of disagreement. To analyse the selected studies, four tables were produced. The first table contains the general characteristics of each study; the second and third list the main descriptive results; and the fourth presents the studies that assessed factors associated with the intake of psychoactive substances.
The search resulted in 367 studies, excluding those duplicated and including the references of the articles consulted. After exclusions by the title or abstract, 65 studies were selected for complete reading. Out of these, 34 were included.5–8 11–40 The reasons for excluding 31 papers are specified in figure 1. The reading of these 34 papers identified 36 studies, since two papers presented results from two independent studies.15 ,25
Most studies were carried out in countries with large land areas, Brazil (n=13), the USA (n=10) and Australia (n=4) being those with the highest number of investigations. Most papers were published starting in the year 2000 (n=30) and involved samples below 500 subjects (n=21), 7 of which had less than 200. About 70% of the studies only researched male drivers.
Out of the 36 studies analysed, 6 also investigated drivers of other motor vehicles.16 ,22 ,34 ,35 ,37 However, the results distinguished between the types of drivers, allowing truck drivers to be evaluated separately.
The method of data collection varied and included surveys at truck stops (n=16), at events promoted for truckers (n=4), with members of trucker associations (n=3), analyses of biological samples from traffic accident victims (n=4), with employees of a shipping company (n=1), and other non-identified sources (n=8). Among the inclusion criteria for the sample, drivers who drove long routes (n=5) and vehicle characteristics (n=7) were the most common. Nineteen studies did not have inclusion criteria for truck drivers (see table 1S in online supplemental material).
Among the 36 investigations, 21 assessed the intake of substances only through truckers’ self-reporting, 13 only through biological samples and two through both.36 ,38 Out of the 15 studies with biological samples, four used forensic data.8 ,16 ,24 Snowden et al24 and Gates et al40 evaluated 71 606 and 10 190 results from biological samples, respectively. The main substances consumed or identified in the studies were alcohol (n=25), amphetamines (n=17), marijuana (n=16) and cocaine (n=13) (see table 1S in online supplemental material).
Tables 1 and 2 describe the main results found in the studies. Among the 23 studies with self-reported information, alcohol was the most frequently reported substance (n=18). Meanwhile, in the 15 studies with biological samples, analyses for identifying amphetamines, marijuana and cocaine were the most common.
The average frequency of self-reported alcohol consumption was 54.3%, ranging from a minimum of 9.9% (Pakistan)37 to a maximum of 91.0% (Brazil)5 (table 1). The identification of alcohol in biological samples was, on average, 3.6%, a minimum of 0.1% (Australia and Norway)22 ,35 and a maximum of 12.5% (USA)8 (table 2).
The average frequency of self-reported amphetamine intake was 29.5%, ranging from 0.9% (Italy)33 to 70.0% (Brazil)30 (table 1). Amphetamines in biological samples averaged 8.5%, from a minimum of 0.2% (Norway)35 to a maximum of 82.5% (Thailand).12
Marijuana and cocaine self-reported intake had average frequencies of 19.3% and 2.9%, respectively (table 1). In the biological samples, averages of 4.7% for marijuana and 1.8% for cocaine were found (table 2). Marijuana use ranged from 0.2%32 to 29.9%,37 while cocaine ranged from 0.1%6 to 8.3%.8 Besides these substances, others were occasionally analysed, such as opioids,6 ,8 ,15 ,16 ,32 ,33 phentermine,7 ,14 codeine,8 ,35 caffeine-based medication,18 pure coffee,27 ,34 energy drinks,27 antihistamines,15 benzodiazepines,6 ,16 among others. Six studies examined only the intake of psychoactive substances in general, without specifying them.11 ,14 ,25 ,27 ,30
Alcohol intake was associated with overweight and obesity in a Brazilian study,28 however in a Japanese study, it was associated with lower average body mass index .23 Alcohol intake was also associated with younger age,23 smoking,23 high blood pressure,23 catholic religion,21 fewer hours of rest,5 involvement in accidents5 and sleep-disordered breathing.23 In Norway, Gjerde et al35 identified that alcohol intake was more frequent among foreign drivers (table 3). The study by Sakurai et al23 was the only one to use adjustment variables (age, smoking and collection site) when analysing factors associated with alcohol intake.
The use of amphetamines was associated with driving during the night shift and with longer time in the profession.5 Another study,39 the only one identified in this review that used multiple regression analysis to identify factors associated with the use of amphetamines, found that younger age, higher income, longer trips, and alcohol consumption were positively associated with self-reported amphetamine intake (table 3), even after controlling for socio-demographic characteristics and religion.
A study carried out in Turkey found a positive correlation between the intake of medication containing caffeine and more hours driving during the day, years at the wheel and degree of stumbling.18 Williamson25 found that, in Australia, the use of stimulating medication was associated with less driver experience, work in medium and small sized companies, income below levels defined by union agreements, productivity-based earnings and fatigue (table 3).
It was also observed that drug intake (drug types were not specified in the studies) was associated with age less than 35 years,35 ,36 male sex,35 contraproductive behaviours (inadequate work, stealing merchandise, failure to report damage to goods transported),11 driving on interstate routes,14 and short or long sleep times (table 3).
Despite its importance to public health, the current review detected that there are still few studies on the prevalence of psychoactive substance use by truck drivers. Most of these studies were carried out in countries with large land areas, such as Brazil, the USA and Australia. This shows that there is greater interest in the subject in areas where road cargo is predominant, especially for long routes, due to a possible relation with the use of psychoactive substances.14
Most studies included a small number of respondents, which highlights the difficulty in identifying and approaching this population group because they usually do not have regular sites for resting, loading and unloading.41 Moreover, half of the studies defined inclusion criteria for selecting drivers. Therefore, the results are representative of specific subgroups and caution must be used in extrapolating the results to the whole trucker community.42 ,43 Nevertheless, they provide an important overview of the psychoactive substance use profile of these professionals.
The prevalence in the intake of psychoactive substances varied greatly, possibly influenced by the methodologies used to obtain data and the different populations studied. The working conditions of these professionals may also be significantly different, such as loading and unloading wait times, the lack of return cargo and the conservation conditions of roads and fleets,44–46 which may stimulate a greater or lower intake of psychoactive substances at work.
Biological analyses identify the presence of alcohol and other substances only if they have been used hours or a few days prior to sample collection.47 Therefore, although biological analyses are more specific, they tend to underestimate the intake prevalence. However, self-reported information can include the use of substances a few minutes prior to the investigation and covers the whole professional life. This methodology is therefore more sensitive but is subject to biases such as memory limitations and, especially, withholding information due to the legal implications of using these substances, thus also underestimating the prevalence. Therefore, the prevalence in studies using biological samples or self-reported information must be analysed separately since the methods used to measure the outcomes, in this case, are not comparable.
Alcohol intake is legal in the countries where the studies were conducted. However, legislation normally forbids alcohol intake prior to or while driving motor vehicles. The Worldwide Brewing Alliance reports that the maximum blood ethanol concentration for professional drivers in the countries where the studies were carried out is as follows: Italy 0.5 g/L, the USA 0.4 g/L, Japan 0.3 g/L, and Australia, Brazil, France and Norway 0.2 g/L.48 These limits, which are related to cultural and oversight issues, partly explain differences in alcohol intake and driving behaviours.
The prevalence of other important psychoactive substances (amphetamines, cocaine and marijuana) also varied. The study carried out by Mongkolsirichaikul et al1,2 in Thailand stands out for identifying an intake of amphetamines in urine samples (82.5%) well above the average compared with other studies using biological samples. According to these authors, the excessive work hours (around 20–22 h) and possible addiction may be the reasons for these high levels.
Self-reporting was a method less frequently used to measure the intake of substances such as amphetamines, marijuana and cocaine given the difficulty in obtaining such information through interviews, especially since these are illicit drugs. Development and validation of questionnaires for obtaining such information anonymously may help further studies that attempt to determine the intake of illicit psychoactive substances in a more reliable way, in addition to representing a simpler and less costly methodology.
Since surveys show a higher prevalence of the intake of psychoactive substances, they are probably more reliable for identifying factors associated with the intake of these substances. These factors included less resting time and working night shifts,5 possibly because the workers need to resort to strategies to keep awake, among which the intake of psychoactive substances stands out. Lower incomes and productivity-based earnings25 were also associated with the use of these substances, which could be explained by the possible motivation of the drivers to increase their income.27 ,30 ,31 In fact, a study conducted in Brazil found that truck drivers with higher incomes and engaged in longer trips were more prone to use amphetamines, probably to remain awake to face their unfavourable working conditions.39 The authors also highlight the higher vulnerability of these individuals to other diseases and the lack of policies that address improvements in their health and working conditions.39 The association between the use of amphetamines and the involvement in accidents5 confirms the risks of using these substances while driving a vehicle.
Unlike the stimulant substances such as amphetamines, alcohol intake was associated more with the drivers’ individual characteristics and health conditions, suggesting that alcohol intake is more common in a social or leisure context.29 ,49 Thus, the harmful effects of alcohol go beyond a greater risk of traffic accidents in truck drivers as it is also related to their health conditions.
The small number of analytic studies exposes a gap in the knowledge in identifying cargo drivers more vulnerable to the intake of psychoactive substances. Studies on representative samples of this population that identify factors associated with the intake of these substances are important, including the use of adjustment variables when needed. Moreover, it is recommendable that future studies use standardised measurements that allow them to be properly compared, including carrying out meta-analyses to estimate joint association measures.
Psychoactive substances have been proved to impair driving and cause a greater risk of traffic accidents.50–52 Therefore, gas stations, trucker stops and companies that employ these professionals must be more closely observed regarding the sale and consumption of these substances. There is some evidence that well planned and well executed multicomponent programmes, when implemented along with community action efforts, are effective in reducing alcohol-derived traffic accidents,53 although no studies were found that were performed specifically in truck drivers. Likewise, regulations for truck drivers, such as suitable working hours and income more compatible with the profession, in addition to better working conditions such as roads and vehicles in good repair, would contribute to a reduction in accidents and the implications these have for individual truck drivers and public health.3 ,54
In summary, the intake of psychoactive substances by truck drivers is a relatively frequent occurrence, although the prevalence varies according to the place and methodology employed. Furthermore, intake seems to be higher when working conditions are poor and can have a direct impact on the health of individual truck drivers and society as a whole due to the increase in traffic accidents. Although from a scientific standpoint the knowledge on the use of psychoactive substances by these professionals still needs to be broadened, the available evidence is more than enough to justify facing and addressing the problem. Well planned and well executed studies are crucial for assessing the effectiveness of strategies for reducing psychoactive substance use by truck drivers before or while driving, in addition to improving their working conditions.
The authors thank the National Council for Scientific and Technological Development (CNPq) for granting a research productivity bursary.
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