Effectiveness of motorcycle helmets for preventing head and facial injuries
2017-02-28T00:24:51Z (GMT) by
SUMMARY Background Malaysia has the highest road traffic crash death rate per 100,000 people in South East Asia. Motorcycle crashes contribute 58% of the total road crash fatalities in the country. The high death rate from motorcycle crashes is often associated with helmet non-use. However, this is not the situation in Malaysia. Helmet wearing rate was shown to be 90% among the riders and 70% with the pillions. Various types of helmets were worn by motorcyclists in this hot climate country. The overall aim of this PhD research was to quantify the association between helmet type, helmet use and helmet components and the distribution and severity of head and facial injuries in riders and pillions in Klang Valley, Malaysia. Methods Three studies were conducted: a case series study, a case control study and a laboratory analysis of crash-involved helmets. Participants in the case series study were people who presented to hospital for treatment of injury or who died from injury, following motorcycle crash in the study area. Cases were recruited from four selected hospitals and a police department. The case control study used data from the head and facial injuries of participants from case series sample together with new data relating to demographic, motorcycle-related and helmet-related factors collected from controls observed at selected roadsides within the same geographical area. Association between helmet use and helmet type and head and facial injuries was determined using logistic regression for both studies. The third study was a laboratory-based biomechanical study, which involved measurement of physical properties of each helmet component; namely the outer shell, the inner liner, the retentive system and the visor. In addition, Fourier Transform Infrared spectroscopy was carried out on the outer shell and visor to determine the type of material and presence of material degradation. Associations between each component and the presence of head and facial injuries in the helmet wearer were assessed using chi square statistics. Logistic regression was carried out to determine the effect of visor type and visor damage on facial injuries. Findings 755 subjects were recruited from the selected centres for the case series. Among all the subjects, 520 sustained head and facial injuries. Of these 520 subjects, 404 sustained head injuries while 391 with facial injuries. There were 391 cases diagnosed with brain injuries. The potential confounders for the relationship between helmet type and helmet fixation and the outcomes of head, brain and facial injuries in the case series study were age, alcohol and illicit substance use, type of colliding vehicle, type of collision and pre-crash speed. Helmet fixation was shown to have a greater effect on the outcomes of head, brain and facial injuries. Adjusted logistic regression showed the following increased risk of adverse outcome for the non-fixed helmet compared to the fixed helmet: i) 5.73 (95% CI 3.38-9.73) for head injury ii) 5.80 (95% CI 3.41-9.89) for brain injury iii) 4.59 (95% CI 2.68-7.85) for facial injury Adjusted logistic regression results for various helmet types are shown below (compared to the full-face helmets): Head injury i) Half head and open-face helmet users: 1.86 (95% CI 0.57-6.09) ii) Tropical helmet users: 2.67 (95% CI 0.65-11.01) iii) Unhelmeted motorcyclists: 4.88 (95% CI 1.23-19.33) Brain injury i) Half head and open-face helmet users: 1.74 (95% CI 0.53-5.75) ii) Tropical helmet users: 2.38 (95% CI 0.57-9.96) iii) Unhelmeted motorcyclists: 4.68 (95% CI 1.17-18.71) Facial injury i) Half head and open-face helmet users: 2.05 (95% CI 0.67-6.24) ii) Tropical helmet users: 3.01 (95% CI 0.75-12.07) iii) Unhelmeted motorcyclists: 13.79 (95% CI 3.28-57.98) Apart from the helmet type, the effect of the visor type on facial injury was assessed (compared to the integrated type). The results are: Facial injury i) Added-on visor users: 0.80 (95% CI 0.45-1.30) ii) Visor-less helmet users: 1.26 (95% CI 0.51-3.11) For the case control study, the same cases as the above were employed and 1510 population controls were observed at the selected roadsides. The potential confounders were found to be the same as for the case series’. The effect of helmet use or fastening status was analysed together with the helmet type. Adjusted logistic regression showed the following results for the non-fixed helmet compared to the fixed helmet: i) 3.32 (95% CI 2.39-4.62) for head injury ii) 3.41 (95% CI 2.44-4.76) for brain injury iii) 2.21 (95% CI 1.54-3.18) for facial injury Adjusted logistic regression results for various helmet types are shown below (compared to the full-face helmets): Head injury i) Half head and open-face helmet users : 2.10 (95% CI 0.74-5.99) ii) Tropical helmet users: 1.22 (95% CI 0.37-3.96) iii) Unhelmeted motorcyclists: 6.91 (95% CI 2.14-22.33) Brain injury i) Half head and open-face helmet users : 2.04 (95% CI 0.72-5.82) ii) Tropical helmet users: 1.10 (95% CI 0.34-3.63) iii) Unhelmeted motorcyclists: 6.53 (95% CI 2.01-21.26) Facial injury i) Half head and open-face helmet users : 1.50 (95% CI 0.57-3.92) ii) Tropical helmet users: 0.78 (95% CI 0.25-2.41) iii) Unhelmeted motorcyclists: 8.12 (95% CI 2.81-23.45) Apart from the helmet type, the effect of the visor type on facial injury was assessed (compared to the integrated type). The results are: Facial injury i) Added-on visor users: 1.57 (95% CI 1.08-2.30) ii) Visor-less helmet users: 1.51 (95% CI 0.79-2.90) The final study, the laboratory analysis did not reveal any significant association between the helmet components and head and brain injuries. However, the adjusted logistic regression on visor damage and facial injuries revealed the following results: i) 5.48 (95% CI 1.46-20.57) for facial injury ii) 4.51 (95% CI 1.08-18.86) for middle face injury Interpretation Helmet use, helmet type and helmet fixation are associated with head, brain and facial injuries. Visor damage is associated with facial injury. This PhD research used the biomechanical epidemiology approach to assess the effectiveness of helmet type and use in reducing head and facial injury. The results provide strong evidence to suggest that proper use is more important than helmet type in providing protection. A population attributable risk (PAR) reduction of 33% in head injury and 50% in death can be expected if all helmets were properly secured. Conclusion and recommendation The effect of improper use and fixation status showed a stronger effect than helmet type in relation to the risk of head, brain and facial injuries. These results provide a new insight into motorcycle injury prevention in Malaysia. Several recommendations for future studies were proposed such as determinants of failure of helmet fixation, helmet biomechanics studies and a helmet type effectiveness study.