METHODS: The study design was a prospective cross-sectional study. The participants involved injured motorcyclists who were admitted in five selected hospitals in Klang Valley, Malaysia. Participants who sustained head injury were selected as the cases while those with injury below the neck (IBN) were selected as the controls. Questionnaire comprising motorcyclist, vehicle, helmet and crash factors was examined. Diagnoses of injuries were obtained from the participants' medical records.

RESULTS: The total subjects with head injuries were 404 while those with IBN were 235. Majority of the cases (76.2%) and controls (80.4%) wore the half-head and open-face helmets, followed by the tropical helmets (5.4% and 6.0% of the cases and controls, respectively). Full-face helmets were used by 1.2% of the cases and 4.7% of the controls. 5.7% of the cases and 6.0% of the controls did not wear a helmet. 32.7% of the cases and 77.4% of the controls had their helmets fixed. Motorcyclists with ejected helmets were five times as likely to sustain head injury [adjusted odds ratio, AOR 5.73 (95% CI 3.38-9.73)] and four times as likely to sustain severe head injury [AOR of 4.83 (95% CI 2.76-8.45)]. The half head and open face helmets had AOR of 0.24 (95% CI 0.10-0.56) for severe head injury when compared to motorcyclists who did not wear a helmet.

METHODS: This was a prospective, cross sectional study recruiting injured motorcyclists from Hanoi, Vietnam hospital. The participants were interviewed by a trained researcher. The participants' helmets were collected post-crash. Initially, the helmets were examined for their type and external characteristics. A 3 cm × 3 cm cut was made on the helmet in the impacted and non-impacted areas (control). These areas were investigated for evidence of POD and presence of micro-cracks and material disintegration. 50 participants were enrolled. Sources of information included questionnaire and laboratory analyses. The helmet factors of interest were age of the helmet, exposure of helmet to sunlight and rain (duration/day) and history of previous impact. Laboratory analyses included Fourier Transform Infra Red (FTIR) for degradation and scanning electron microscopy (SEM) for micro-structural examination.

RESULTS: Majority of the helmets was the open-face type, 40 (80.0%). 31 (62.0%) helmets aged less than three years (LTY) and 19 (38.0%) were three years old or more (MTY). 19 (61.3%) of the LTY helmets and 12 (63.2%) MTY helmets showed evidence of POD. The duration of helmet exposure to sunlight was between 93 to 6570 hours (mean 2347.74 hours; SD 1733.39). The SEM showed 15 helmets (30%) with micro-fractures, 21 helmets (42.0%) with material disintegration. Prolonged uv exposure to the ABS helmets resulted in changes in the helmet material in the form of material disintegration and microcracks and this association was statistically significant (p = 0.03).