Two-wheeled motorcyclists are more likely to die in road traffic accidents. A motorcyclist is 34 times more likely to die and 8 times more likely to be injured than a car driver in a road accident [1] . These accidents are a major cause of death. This is why road safety has become a major and growing public health issue worldwide [2] . The advent of new, powerful and financially more accessible models has been accompanied by an increase in the frequency of accidents and mortality from serious injuries caused by motorbikes around the world, particularly in low-income countries [3] . It should also be noted that motorised two-wheelers are constantly on the increase in most countries, and are currently distributed as follows: 77% in Asia, 14% in Europe, 5% in Latin America, 2% in North America, 1% in the Middle East and 1% in Africa [3] . In the Democratic Republic of Congo, there are currently more than 400,000 motorbikes in the provincial city of Kinshasa alone, according to the number-plate register (provincial ministry of transport). According to the WHO, they are a vulnerable group, accounting along with pedestrians and cyclists for half of all road deaths worldwide. While the risk of death is often highlighted, the risk of serious injury, and often lifelong disability, is also higher. The number of years of life lost or spent in suffering and disability is considerable. In France, for example, the fall in the number of fatalities among car drivers between 2001 and 2005 was 42%, while that for motorcyclists was just 21.8%. The proportion of motorbike users killed increased, even though they accounted for only 1.1% of traffic [4] . A multicentre cohort study using data from the French National Trauma Registry (Trauma Base) from 1 January 2019 to 20 December 2022 found that, of the 5233 two-wheeled trauma victims, 4094, or 78%, were motorcyclists [5] . In Cotonou, Benin, out of a population of 9.8 million, two-wheeled vehicles account for 80% of means of transport, and the incidence of motorbike accidents was 1.77%, with a fatality rate of 5.2% [6] . Motorcyclists accounted for 57% of head injuries treated at Lomé hospital between January 2015 and December 2017 [7] . Motorbikes were involved in 70.3% of cases, and motorcyclists were the victims most often involved (76%) in road traffic injuries seen in the emergency department of a hospital in N’djamena, Chad, between July and December 2020 [8] . In a single-centre study in Senegal, moped accidents accounted for 57.8% of victims, with a mortality rate of 4.6% [9] .

In Kinshasa, the increased need to travel in response to society’s current problems, such as the cost of petrol, saturation of the road network and the growing need for cheaper means of transport, the use of motorised two-wheelers is constantly on the increase, with over 400,000 motorbikes currently registered according to the provincial Ministry of Transport. In addition to the growing number of motorbikes on the road, it is deplorable to note the failure of motorcyclists to obey the highway code, resulting in a large number of avoidable accidents, some of which are fatal and others serious. However, motorbikes have become an almost indispensable means of transport in certain parts of the city. The renewed interest in the use of motorbikes could be accompanied by a deterioration in accident figures. There is no pre-hospital care in the city of Kinshasa or anywhere else in the Democratic Republic of Congo. Universal health cover has not yet been extended to trauma patients, and local health facilities are not always equipped to deal with serious trauma, which has a very high mortality rate in Kinshasa. Patients have to provide their own medical care, which is often very expensive. Trauma victims are brought to hospital by people of goodwill, sometimes on motorbikes, despite the fact that any injuries they suffer may be more serious. Nsiala has conducted two studies: one in 2014 [10] which found a mortality rate of 90.7% for serious trauma victims. In 2018 [11] , after the establishment of a care network that unfortunately was not universally supported, this mortality rate had fallen to 73.3%. However, these studies did not look specifically at severe motorbike trauma patients admitted to intensive care, and to date no study has been devoted to them. We therefore thought it would be useful to carry out this study to determine the mortality of patients with severe motorbike trauma admitted to intensive care units in the city of Kinshasa, and the factors associated with it.

This study was conducted to determine the mortality rate of severe motorcycle trauma patients, and it is very high in this series, at 71.8%. Analysis of the data collected in this study on severe trauma patients admitted to six care centres between 2021 and 2023 reveals several factors influencing patient prognosis, including age, head injury, oxygen saturation, ISS, and Glasgow Coma Scale (GCS).

Severe motorcycle trauma affects young patients, as noted by others [6] , therefore of an economically productive age, male [6] [12] , and often married, thus responsible for families, and unfortunately, they will die seven times out of ten. This high mortality rate can also be explained by the fact that there is no pre-hospital care, with patients being taken to any health facility, sometimes with no equipment or skills at all for these types of patients. As a result, the majority of patients arrived at the hospitals concerned after having passed through a small outlying centre—a factor that increases mortality. It should be pointed out that the current government has introduced universal health cover, a major innovation, but it does not yet cover trauma victims and is limited to pregnant women. What’s more, there is no level one trauma centre in Kinshasa. The Brazilian study [13] also found a male predominance, with a mean age of 31 years, corroborating the results of this study. This reflects the seriousness of this problem and its economic consequences for the country. Indeed, not only is the care of severely injured people very expensive for families, but also the victims are those who work to feed their families, and the fact that they are sick is doubly detrimental for them, for the family and for society. And we have not followed the distant future of survivors in terms of after-effects which are often serious. In the literature review published by Chamaphom [14] , the trauma, whether mild, serious or fatal, concerned more young people under 30 years of age than those over 50 years of age. In the Madougou study [6] , the injury mechanism was often a motorcycle-on-motorcycle collision as in our study and head and lower limb injuries were as frequent as in our study. Rearderson in Tanzania [15] also noted that the accident mechanism was a motorcycle-on-motorcycle collision in 35%, a figure close to our results (40%). Other authors have reported the predominance of motorcycle versus vehicle collisions, reflecting the diversity of mechanisms predominating according to the studies. A Kenyan study [16] found that victims were often unmarried, unlike our results, with 50% of married people suggesting that motorcyclists in our context are responsible for families who struggle to feed their families.

The mortality rate in this series is the highest of all the series in the literature; 5.2% in Benin [6] , 4.6% in Senegal [9] , 5.2% in the James study [5] . However, it should be emphasized that their studies involved all trauma patients, while ours only focused on severe trauma patients. Thus, 4 out of ten patients had several injuries, reflecting the severity of the trauma, just as the Guinean study also found that 43% of patients had at least two injuries [17] . Authors have reported higher mortality among helmet wearers, 0% to 2.8%, compared to 10 to 14.8% among non-helmet wearers [18] . In the Ethiopian study [19] , the victims were the driver in 42%, the pedestrian in 35.5% and the passenger in 25%, corroborating the results of our study for the predominance of the driver, but the passenger was often the victim in our series because the motorcycle is used essentially as a means of transport and the driver is therefore always accompanied by passengers. Cranioencephalic lesions predominated in this study, unlike the Brazilian study, which accounted for only 3% of the cases. This difference was likely due to the sample size of 62 patients [13] . However, other studies [20] [21] have found a predominance of cranioencephalic lesions, consistent with the results of our study. Wade’s study [9] , which examined all types of trauma, found a predominance of skin lesions and fractures of the lower and upper limbs. The victims were mainly drivers (56%), as in our study.

High ISS, low Glasgow Coma Scale (GCS), and poor cardiorespiratory parameters at admission were factors or predictors of death, as Boniface [22] reported that the severity of the lesions was an independent factor in mortality. Hypotension and hypoxia are major secondary cerebral disorders of systemic origin increasing the mortality of traumatic brain injuries which occupied an important place in this series. This observation is justified by the fact that injuries affecting the brain, the circulatory system and the respiratory system directly endanger life. The use of vasopressors, which appears to predict mortality, is in fact a marker of severity, as they are used to treat arterial hypotension or shock. Thus, in the study of Doléagbénou [7] , out of 321 patients who suffered cranioencephalic trauma, 181 involved motorcycles. This shows the severity and frequency of motorcycle injuries. In this Togolese series [7] , a Glasgow score of less than 9/15 was associated with mortality, corroborating the results of our study. The analysis shows that patients aged 60 and over have a higher risk of mortality, confirming its pejorative role. Other studies, notably that of Boniface [22] carried out in Tanzania, found that mortality concerned the age group of 18 to 40 years. The difference would come from the way in which the age grouping was carried out. The absence of helmets in half of our patients did not paradoxically influence mortality in our series, probably because of the size of the sample.

Indeed, the literature review conducted by Konlan [23] on road traffic accidents in Africa found that not wearing a helmet was significantly associated with mortality (p = 0.007). 78% of victims did not wear helmets in the Iamtrakul study [12] , results close to those of our study. A typical literature review study conducted in Bogota [24] showed that male gender, married status, high level of education and driving one’s own motorcycle were factors associated with wearing a helmet; age had no influence. However, this factor (wearing a helmet) did not emerge as a predictor of mortality in this study, probably because of the sample size. However, in the city of Kinshasa, only the driver wears a helmet and never the passenger. In the Thai study [12] , motorcycle accidents, which accounted for 93% of all accidents, were more frequent at night than during the day, a parameter that was not used in our study. Similarly, alcohol consumption, which was present in 33% of accidents in the Thai study, was not used in our study due to the weakness of retrospective studies relying on information found in the files.

In the Guinean study [17] , age, sex, and victim category were not predictors of mortality as in our study, except for age, while a low Glasgow Coma Scale score was, corroborating our results. Lack of helmet use, alcohol consumption, driver experience, excessive speed and poor road conditions are risk factors for motorcycle accidents known in the literature but which could not be analysed this study due to the retrospective nature [25] - [27] . However, not wearing a helmet (half in this study), poor road conditions, alcohol consumption and excessive speed are common occurrences in our environment. Our results are similar to those found by Sawadogo [28] Ouagadougou with his MGAP (Mechanism, Glasgow coma scale, Age, arterial Pressure) score is re liable in predicting the mortality of serious injuries.

This study confirmed that severe motorcycle trauma primarily affects young people, with a high mortality rate. The predictors or factors associated with mortality are those described in the literature and linked to the severity of the injury: a low Glasgow Coma Scale (GCS), low blood pressure, low systolic pressure, and low oxygen saturation upon admission, as well as a high ISS.

A prospective study including all major hospitals that receive trauma patients seems necessary to draw generalizable conclusions for the entire city of Kinshasa.

Alex Kalonji: Study design, data collection, and manuscript writing.

Wilfrid Mbombo: Study design, data collection, and manuscript writing.

Joseph Nsiala: Study design and manuscript writing.

Alhonse Mosolo: data collection and manuscript reading.

Leader Lawanga: Statistical analyses.

All other authors: Manuscript reading.

We would like to thank the managers of the hospitals that participated in the study, as well as those who contributed to data collection, including Vitaline Kanyeba from the Monkole Hospital Centre and the assistants from the Anaesthesia and Resuscitation Department of the University Clinics of Kinshasa.