Alcohol (ethanol) is a widespread euphoriant and acts as a central nervous system depressant. It is absorbed from the gastrointestinal tract and the rate of absorption depends on the amount consumed, the concentration of ethanol in the drink, the interaction with medicinal drugs, the presence of food in the stomach and the duration of the digestion process. Following absorption, approximately 95% of ethanol is metabolized in the liver and excreted in urine, and 5% is excreted, without undergoing metabolism, through the lungs, urine or sweat. The effects of ethanol's action on the central nervous system include cognitive, judgment and memory impairment, relaxation, sensory dysfunction (e.g., balance, speech, vision, reaction time and hearing) and motor impairment. In addition, alcohol consumption at high concentrations (binge drinking) may cause vomiting, amnesia or even death (1).

Alcohol is positively associated with increased morbidity and mortality in a number of diseases and violent injuries among which road traffic accidents (RTAs) are present at a high ranking status (2). Canada, the United States of America (USA) and New Zealand are, in turn, the 3 top countries globally with the highest percentage of RTA-related fatalities associated with alcohol consumption (3). In the European Union, alcohol is one out of the 3 main risk factors accountable for 40% of poor health and premature deaths. Globally, RTA-related injuries are the leading cause of mortality among teenagers and young adults (aged between 15 and 29 years) (3), which highlights driving under the influence of alcohol as a major risk factor for the demographic and socioeconomic status of any country. In 2012, the age-standardized death rates (ASDR) of alcohol-related RTAs in Greece was estimated to 31.5/100000 individuals (4).

Previous studies, such as those conducted in Finland (5), Mexico (6) and South Africa (7), have verified that driving under the influence of alcohol impairs attention and cognitive capacities. According to Sauber-Schatz et al (8), in the USA and 19 other high-income countries, driving under the influence of alcohol is often associated with the absence of the use of seatbelts, something that increases the risk of injuries. In Thailand, Tongklao et al (9) demonstrated that alcohol consumption was associated with the absence of the use of driving helmets, while in the United Kingdom, Clarke et al (10) associated alcohol-impaired driving with driving at high speeds. Furthermore, fatal alcohol-related RTAs among vulnerable road users (pedestrians or cyclists) is a significant issue in a number of countries, such as in Canada (11), Scotland (12) and SriLanka (13).

Driving under the influence of drugs is also considered a serious issue affecting public health. Li et al (14) and Romano et al (15) in the USA, Simonsen et al (16) in Denmark, Imad et al (17) in Jordan, Gadegbeku et al (18) and Martin et al (19) in France, Veldstra et al (20) in The Netherlands and Brubacher et al (21) in the United Kingdom also indicated that the combination of alcohol consumption and the use of psychoactive substances was associated with an increased risk of a fatal RTA.

In Greece, previous studies have highlighted the role of alcohol consumption and the use of psychoactive substances in RTA-related fatalities. During the period between 1995–1997, 41% of the drivers involved in traffic accidents were found to be positive for alcohol consumption (22). During the period between 1998–2004, male drivers aged between 20 and 40 years were found more likely to be involved in alcohol-related RTAs (23). In Athens, the capital of Greece, almost a third of RTA-related fatalities have been found to be associated with the use of alcohol, psychoactive drugs or both (24). In addition, in a 3-year study (2006–2008) (25) in the region of Central Macedonia, it was observed that alcohol was detected in 28% of the drivers involved in a fatal collision.

The objective of this study was to present the current situation concerning the involvement of alcohol and other psychoactive substances in fatal RTAs over a 7-year period (2011–2017) in Greece. For this purpose, the results of the toxicological investigations from the database of the Department of Forensic Medicine and Toxicology of the National and Kapodistrian University of Athens were retrieved and evaluated according to the blood alcohol concentration (BAC), the presence of psychoactive substances, the victim (car driver, motorcyclist, pedestrian, or passenger), the sex and age of the victims of the RTAs, and the date the accident occurred (day, month and year).

The Department of Forensic Medicine and Toxicology of the National and Kapodistrian University of Athens is authorized to perform the toxicological investigation of traffic accidents that occur in the major part of the country. A total of 5,716 autopsies were conducted between January, 2011 and December, 2017. Of these, 1,841 (32.2%) were RTA-related fatalities. The victims included car drivers, motorcyclists, passengers and pedestrians. The results were classified according to sex, age and the type of victims, as well as the day, the month and year, on which the accident occurred.

Toxicological investigation was performed according to the Greek legislation (Ministerial Decision No. 2500/15/135, Greek Government Gazette B 2077 of September 19, 2011). The results of the toxicological analyses were classified according to the BAC and the category of the psychoactive substance detected. Alcohol analysis was performed in whole blood samples using a headspace-gas chromatography-flame ionization detector (HS-GC-FID) method (26). Psychoactive substances were detected in blood and urine samples using a screening immunochemical method (VIVA-E, Siemens). Their presence in the blood was confirmed by validated in house gas chromatography/mass spectrometry (GC/MS) methods. BACs were classified according to the limits dictated by the Greek Road Traffic Code where the maximum permitted level of alcohol in blood is 50 mg/dl.

The highest percentage of fatal RTA-related victims was observed in 2016 (n=360, 19.5%), followed by 2014 (n=298, 16.2%), 2015 (n=294, 16%) and 2017 (n=290, 15.8%) (Fig. 1). A total of 79.2% (n=1,458) of the RTA-related victims were male and 20.8% (n=383) were female, respectively. In 1,371 cases (74.5%), the victims were car drivers and motorcyclists. The majority of the victims were car drivers (43.2%, n=795), and predominantly individuals aged between 21 and 30 years (20.3%, n=373) (Table I). Accordingly, young individuals (aged 21–30 years) were over-represented among the fatally-injured motorcyclists (142 out of 576 cases, 24.7%) and passengers (44 out of 162 cases, 27.2%), as presented in Table I. On the other hand, the majority of fatally-injured pedestrians (175 out of 308 cases, 56.8%) were over 71 years of age (Table I).

Alcohol was detected in 40.7% (n=749) of the RTA-related victims (Fig. 1). Of these, 464 (61.9%) had consumed alcohol alone, while the rest had consumed alcohol in combination with at least one psychoactive drug (data not shown). In total, 87.3% (n=654) of the RTA-related victims who were alcohol-positive were male and 12.7% (n=95) female victims, respectively. A total of 373 of the RTA-related fatalities who were alcohol-positive (20.3%) were car drivers and the majority of the victims of alcohol-related RTAs were male car drivers and motorcyclists (n=557, 74.4%) (Fig. 2). Additionally, 55.7% (n=417) of the victims of alcohol-related RTAs were found with a BAC >110 mg/dl and were mostly male (Table II).

Young drivers (21–30 years of age) driving under the influence of alcohol were more often involved in fatal RTAs than drivers of other ages (Fig. 3). The percentage of RTA-related fatalities associated with alcohol consumption was higher in the 21–30-year age group compared to the other age groups (Table III).

Alcohol was detected in 44% (603 out of 1,371 cases who were car drivers and motorcyclists) of drivers involved in RTAs. In addition, 42.3% of the fatally injured pedestrians in alcohol-related RTAs were aged over 71 years (Fig. 3).

As regards the seasonality of fatal RTAs, these occurred more often during the summer months (June to August), while 38% occurred over the weekend (data not shown). Psychoactive substances were detected in 348 cases (18.9%) [cannabis in 46.6% (n=162) of these, benzodiazepines in 25.9% (n=90), opiates in 16.4% (n=57) and cocaine in 11.1% (n=39)]. Of these, 91.4% (n=318) were males and 8.6% (n=30) were females, as shown in Table IV. The age groups of 21–30 years and 31–40 years presented a higher percentage of cannabis use [16.7% (n=58), 11.5% (n=40), respectively] than other substances and the age group of 41–50 years had a higher percentage of benzodiazepines use (8.9%, n=31) (Table IV).

Benzodiazepines, cocaine and opioids were detected more frequently in car drivers, while cannabis was detected more often in motorcyclists (Fig. 4). In total, 59 (3.2%), 39 (2.2%), 12 (0.6%) and 2 (0.1%) of the victims had used cannabis, benzodiazepines, opioids and cocaine alone, respectively (data not shown). The percentage of victims under the influence of alcohol in combination with other psychoactive substances was estimated at 4.5% (n=83) (data not shown). In total, 54 (2.9%), 14 (0.7%), 11 (0.5%) and 3 (0.2%) of the victims had used alcohol in combination with cannabis, benzodiazepines, cocaine and metabolites of heroin, respectively (data not shown).

In this study, alcohol was detected in 40.7% of the RTA-related victims and 44% of the drivers were found to be positive for alcohol use. According to previous studies conducted in Greece (22,23), during the period between 1995–1997 and 1998–2004, drivers involved in alcohol-related RTAs were 37 and 41%, respectively. In addition, the majority of BAC-positive fatalities were car drivers and motorcyclists, in accordance to the findings of Hamnett et al (12) in Scotland and those of Costa et al (27) in Portugal. Papadopoulos et al (24) reported that the majority of BAC-positive RTA-related fatalities were motorcyclists in Athens, Greece. This finding is expected, as many individuals in Athens prefer to use motorcycles for transport in order to avoid traffic congestion.

The present study revealed that the most active and productive age group (21–30 years old) were the most common victims of RTA-related fatalities associated with alcohol consumption. Accordingly, Papadodima et al (23), in a 7-year study (1998–2004) conducted in Greece, reported that the majority of drivers involved in fatal alcohol related traffic accident were young drivers.

In this study, fatal alcohol-related RTAs more often occurred during weekends and the summer period than during weekdays. These results are in accordance with those presented in the study by Ampanozi et al (25) in the region of Central Macedonia, Greece, and with those of Anowar et al (28) in Canada. Weekends were characterized by a higher prevalence of driving under the influence of alcohol, driving under the use of drugs and driver fatigue-related RTAs, as presented in the studies by Foster et al (29) in Switzerland and Furr-Holden et al (30) in the USA. According to EU road safety statistics for 2017, holiday seasons (July and August) are associated with a higher incidence of fatal RTAs than other periods of the year (31). Odero et al (32) reviewed all the published and unpublished reports on RTAs in developing countries from 1966 to May, 1994 and reported that in 79% of the studies, collisions occurred between Friday and Monday.

In the present study, cannabis, benzodiazepines, opiates and cocaine were detected in 162 cases (8.8%), 90 cases (4.9%), 57 cases (3.1%) and 39 cases (2.1%) of the victims of RTAs, respectively. The percentage of victims driving under the influence of alcohol in combination with other psychoactive substances was estimated at 4.5%. Other studies conducted in the USA (14,33), Norway (34) and Brazil (35) reported that driving under the influence of alcohol or drugs poses a significant issue. The frequency and category of the detected psychoactive substances is variable among countries, as the profile of the drug victim in each country differs and depends on the socioeconomic status, the policy that each country enforces regarding alcohol consumption and the use of prescription and illicit drugs. According to the World Drug Report (2018), in 2016, the use of cannabis, opiates, amphetamines and prescription stimulants was predominant in Asia, the use of cocaine in Europe and the use of opiates in America (36). Moreover, male victims presented with a higher percentage of psychoactive substance use compared to female victims, in accordance to the study by Gjerde et al (37) in Norway.

The results of the present study revealed that 1,371 cases of RTA-related fatalities during the period between 2011–2017 were drivers (car drivers and motorcyclists). Papadodima et al (23) reported that during the period between 1998–2004 in Greece, a much higher number (3,167 drivers) of drivers was involved in a fatal traffic accident. This noticeable reduction in RTAs in our country over the past decade may be attributed to the upgrade of country's road network and the development of new and more sophisticated car technologies. It should be noted that the economic crisis in Greece resulted in a reduction in the number of fatal RTAs. This was also observed in Great Britain during the period between 2007–2010 (38). Furthermore, the construction of the Athens Metro (suburban railway) in the year 2000 in Athens contributed significantly to the improvement of the city's traffic circulation and motivated many individuals not to use their own vehicle for transportation.

This study indicated that 43.2% of the victims of RTAs were car drivers, in accordance with the study by Gopaul et al (39) in Trinidad. Previous studies conducted in other countries, such as in the Ivory Coast (40), China (41), Russia (42) and Pakistan (43) have reported that pedestrians have a higher incidence of traffic accident mortalities. Those differences among countries may be attributed to the predominant types of transportation, economic status, proper infrastructure for pedestrians and cultural awareness. For example, in the African Region, individuals prefer walking and cycling, while in the South-East Asia Region and the Western Pacific Region, individuals mainly used motorcycles as a method of transportation (3).

The findings of this study demonstated that young males were over-represented in fatal road traffic accidents, in accordance with the studies by Ramadani et al (44) in Kosovo, Majdan et al (45) in Austria and Reddy et al (46) in India. Other studies have investigated the reasons for the high occurrence of deaths of young individuals involved in RTAs. In the USA, Lambert-Bélanger et al (47) revealed that aggressive driving constituted a high risk factor of fatal RTAs in young individuals and Weiss et al (48) in New Zealand, reported that rarely or not wearing a seatbelt at all led to road traffic-related deaths among individuals aged between 15–24 years. Furthermore, according to the study by Khadem-Rezaiyan et al (49) in Iran, using a cell phone while driving is a major high-risk behavior of individuals aged 30±13 years. Finally, Abayomi et al (50) in Nigeria, and Hingson et al (51) in the USA, reported that driving under the influence of alcohol was responsible for the incidence of fatal RTAs among young individuals.

On the other hand, this study reported that elderly individuals present the majority of fatally injured pedestrians. Accordingly, Kaimila et al (52) in Japan, and Rolison et al (53) in the United Kingdom, reported that elderly pedestrians were more susceptible to road traffic accidents when compared to younger individuals. According to the studies by Zito et al (54) in Switzerland, Cicchino and McCartt (55) and Doroudgar et al (56) in the USA, the main cause seemed to be a consequence of the aging process, which leads to a decrease in balance, hearing, vision, reaction time, muscle mass and bone mass in older individuals.

A limitation of the present study was that victims <18 years of age were excluded. In addition, no statistical analysis was performed in this study to determine statistical significance. Thus, further studies are required in order to better determine the significance of the role of alcohol and psychoactive substances in RTAs in Greece.

In conclusion, the present descriptive study presents the impact of alcohol consumption and the use of psychoactive substances in fatal RTAs in Greece. Driving under the influence of alcohol and/or psychoactive substances is associated with careless driving, which could lead to fatal results. Appropriate countermeasures are imperative in order to reduce fatal collisions involving young individuals, including driving simulator training, the development of novel interventions within the field of driving and a more educational approach on driving safety focusing on social networking. Furthermore, it is necessary that state authorities plan educational campaigns and advertisements highlighting the harmful effects of alcohol use and/or other psychoactive substances use while driving.