Effectiveness of cycle helmetsBMJ 1994; 308 doi: https://doi.org/10.1136/bmj.308.6937.1164a (Published 30 April 1994) Cite this as: BMJ 1994;308:1164
- Patricia Priest
- Public health medicine registrar, Department of Community Health, School of Medicine, University of Auckland, Private Bay, 92 109, Auckland, New Zealand.
EDITOR,--In their analytical epidemiological study of the effectiveness of cycle helmets, Steven Thomas and colleagues' discussion of biases was incomplete and possibly misleading.1 In the second paragraph of the discussion they describe some sources of bias that would cause their data to underestimate the strength of the association between wearing a helmet and reduced risk of injury to the upper head. They then state: “Similarly, reduction in the estimated risk of upper head injury would have been greater if …