Risk taking is influenced by people's perception of safety and danger

EDITOR—Rivara et al in their editorial on bicycle helmets offer the study by Cook and Sheikh in the same issue as representative of evidence that has persuaded them of the benefits of wearing helmets. 1 2 The first calculation presented by Cook and Sheikh does not inspire confidence in the rigour of their study—35 056 cycling injuries are 0.28%, not 2.8%, of 12.6m hospital emergency admissions. They say that the 24.2% decrease in numbers of head injuries that they report from 1991 to 1995 is attributable to the increase in helmet wearing but present no evidence either of the magnitude of this increase or of any change in mileage cycled.

The official record shows that the number of cyclists killed and seriously injured per 100m km cycled increased by 8.6% whereas the figure for all drivers and riders decreased by 16.7% (for fatalities the figures are 0 and −20% respectively). These statistics indicate that any decrease in cyclists' head injuries over this period has been more than offset by increases in other serious and fatal injuries among cyclists.

In their Cochrane review, Thompson et al used the dubious tactic of attributing to one of us (MH) the argument that helmeted cyclists feel “invincible”—a word not used—“and therefore ride in a more reckless manner,” and they then say that they believe these arguments to be specious.3 In their editorial they again attribute to MH an argument he does not make—that the risk to cyclists is unchanged by helmet wearing. The wording of the relevant part of his report states: “Cyclists are less likely to ride cautiously when wearing a helmet owing to their feeling of increased security. In this way, they consume some, if not all, of the benefit that would otherwise accrue from wearing a helmet.”4

Thompson et …