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Association of driver air bags with driver fatality: a matched cohort study

BMJ 2002; 324 doi: https://doi.org/10.1136/bmj.324.7346.1119 (Published 11 May 2002) Cite this as: BMJ 2002;324:1119
  1. Peter Cummings, associate professor (peterc{at}u.washington.edu)a,
  2. Barbara McKnight, professorb,
  3. Frederick P Rivara, professora,
  4. David C Grossman, professora
  1. a Harborview Injury Prevention and Research Center, 325 Ninth Avenue, Box 359960, Seattle, WA 98104-2499, USA
  2. b Department of Biostatistics, School of Public Health and Community Medicine, University of Washington, Seattle, WA, USA
  1. Correspondence to: P Cummings
  • Accepted 19 April 2002

Abstract

Objective: To estimate the association of driver air bag presence with driver fatality in road traffic crashes.

Design: Matched pair cohort study.

Setting: All passenger vehicle crashes in the United States during 1990-2000 inclusive.

Subjects: 51 031 driver-passenger pairs in the same vehicle.

Main outcome measures: Relative risk of death within 30 days of a crash.

Results: Drivers with an air bag were less likely to die than drivers without an air bag (adjusted relative risk 0.92 (95% confidence interval 0.88 to 0.96)). This estimate was nearly the same whether drivers wore a seat belt (adjusted relative risk 0.93) or not (0.91). Air bags were associated with more protection for women (0.88 (0.82 to 0.93)), than for men (0.94 (0.90 to 0.99)). Drivers wearing a seat belt were less likely to die than unbelted drivers (0.35 (0.33 to 0.36)). Belted drivers with an air bag were less likely to die than unbelted drivers without an air bag (0.32 (0.30 to 0.34)).

Conclusions: If the associations are causal the average risk of driver death was reduced 8% (95% confidence interval 4% to 12%) by an air bag. Benefit was similar for belted and unbelted drivers and was slightly greater for women. However, seat belts offered much more protection than air bags.

What is already known on this topic

What is already known on this topic Studies have estimated that driver air bags reduce the risk of death in a road vehicle crash by 10-14%

These studies disagree as to whether benefit is greater for drivers wearing a seat belt or for unbelted drivers

What this study adds

What this study adds Having an air bag was associated with an 8% reduction in the risk of death, whether the driver was belted or not

The reduction in risk was greater for women (12%) than for men (6%)

Seat belts provided much greater protection, with seat belt use reducing the risk of death by 65% (or by 68% in combination with an air bag)

Footnotes

  • Contributors PC initiated and designed the study, performed the data analysis, and wrote the first draft. BM provided advice about the statistical methods. All authors helped interpret the results and revise the manuscript. PC is guarantor for the study.

  • Funding This study was supported by grants R49/CCR002570 and R49/CCR019477-01 from the Centers for Disease Control and Prevention, Atlanta, GA.

  • Competing interests None declared.

  • Embedded ImageA table comparing the results with those of previous studies appears on bmj.com

  • Accepted 19 April 2002
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