Is body mass index a risk factor for road traffic injuries

Drivers who are overweight or underweight are at greater risk of suffering an injury in a road accident than people of average size, according to a study of deaths and injuries from motor vehicle accidents in New Zealand.

The study appears in the current issue of the International Journal of Epidemiology (IJE), edited in the Department of Social Medicine at the University of Bristol.

Dr Gary Whitlock and colleagues studied people who had been seriously injured or killed between 1988 and 1998 while driving a motor vehicle. The subjects were categorised into four groups according to their Body Mass Index (that is their ‘weight for height’).

The most obese drivers were found to have been twice as likely to experience injury over the study period than people of average size. This may be due to the fact that overweight people are more likely to suffer from sleeping disorders (such as sleep apnoea which causes a cessation of breathing while asleep, making it difficult to sleep for long periods) and therefore may be more likely to fall asleep at the wheel.

The thinnest people were also more likely to have had an injury compared to those in the middle weight range, which may be due to the higher risk of bone fractures in thinner people.

Seatbelts are designed for average-sized people so this may also be a factor.

Dr Whitlock undertook this research during the tenure of a Health Research Council of New Zealand training fellowship at the University of Auckland, working with colleagues at the universities of Auckland, Sydney and Oxford.