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Table 1 Covariates and outcome of adult motorcycle traffic accident helmet users and nonusers before and after propensity score matching (1:1 matching)

From: The protective effect of helmet use in motorcycle and bicycle accidents: a propensity score–matched study based on a trauma registry system

  Before matching After matching
Covariates Helmet use
Yes n = 7735
Helmet use
No n = 863
Odds ratio
(95%CI)
P Helmet use
Yes n = 856
Helmet use
No n = 856
Mean
Difference
Standardized
Difference
Age 46.0 ± 17.5 48.8 ± 18.6 <0.001 48.6 ± 18.6 48.6 ± 18.6 −0.01168 −0.06(%)
Sex
 Male 4248(54.9) 592(68.6) 0.6(0.48–0.65) <0.001 588(68.7) 588(68.7) 1.0(0.82–1.23) 0.00(%)
 Female 3487(45.1) 271(31.4) 1.8(1.54–2.09) <0.001 268(31.3) 268(31.3) 1.0(0.82–1.23) 0.00 (%)
Comorbidity
 DM 831(10.7) 106(12.3) 0.9(0.69–1.07) 0.169 102(11.9) 102(11.9) 1.0(0.75–1.34) 0.00 (%)
 HTN 1539(19.9) 201(23.3) 0.8(0.69–0.97) 0.019 197(23.0) 197(23.0) 1.0(0.80–1.25) 0.00 (%)
 CAD 156(2.0) 23(2.7) 0.8(0.48–1.17) 0.206 20(2.3) 20(2.3) 1.0(0.53–1.87) 0.00 (%)
 CHF 27(0.3) 7(0.8) 0.4(0.19–0.99) 0.076 4(0.5) 4(0.5) 1.0(0.25–4.01) 0.00 (%)
 CVA 95(1.2) 15(1.7) 0.7(0.41–1.22) 0.206 11(1.3) 11(1.3) 1.0(0.43–2.32) 0.00 (%)
 ESRD 2(0.0) 0(0.0) 1.000 0(0.0) 0(0.0)
Outcome
GCS 14.4 ± 2.1 12.8 ± 3.8 <0.001 14.4 ± 2.0 12.8 ± 3.8 <0.001
 ≤ 8 305(3.9) 145(16.8) 0.2(0.16–0.25) <0.001 34(4.0) 145(16.9) 0.2(0.14–0.30) <0.001
 9–12 256(3.3) 79(9.2) 0.3(0.26–0.44) <0.001 31(3.6) 77(9.0) 0.4(0.25–0.58) <0.001
 ≥ 13 7174(92.7) 639(74.0) 4.5(3.76–5.34) <0.001 791(92.4) 634(74.1) 4.3(3.17–5.73) <0.001
AIS ≥ 3, n (%)
 Head/Neck 1288(16.7) 399(46.2) 0.2(0.20–0.27) <0.001 149(17.4) 398(46.5) 0.2(0.19–0.30) <0.001
 Face 22(0.3) 7(0.8) 0.3(0.15–0.82) 0.022 4(0.5) 7(0.8) 0.6(0.17–1.95) 0.364
 Thorax 685(8.9) 105(12.2) 0.7(0.56–0.87) 0.001 98(11.4) 104(12.1) 0.9(0.70–1.25) 0.653
 Abdomen 192(2.5) 21(2.4) 1.0(0.65–1.61) 0.930 21(2.5) 21(2.5) 1.0(0.54–1.85) 1.000
 Extremity 1898(24.5) 138(16.0) 1.7(1.41–2.06) <0.001 190(22.2) 137(16.0) 1.5(1.17–1.91) 0.001
ISS, median (IQR) 8(4–10) 10(5–18) <0.001 9(4–12) 10(5–18) <0.001
 < 16 6570(84.9) 530(61.4) 3.5(3.05–4.12) <0.001 687(80.3) 524(61.2) 2.6(2.07–3.20) <0.001
 16–24 829(10.7) 224(26.0) 0.3(0.29–0.41) <0.001 144(16.8) 223(26.1) 0.6(0.45–0.73) <0.001
 ≥ 25 336(4.3) 109(12.6) 0.3(0.25–0.40) <0.001 25(2.9) 109(12.7) 0.2(0.13–0.32) <0.001
Hospital LOS (days) 9.5 ± 9.7 12.0 ± 12.9 <0.001 9.5 ± 9.7 12.0 ± 12.9 <0.001
ICU
 Patients, n (%) 1291(16.7) 338(39.2) 0.3(0.27–0.36) <0.001 156(18.2) 336(39.3) 0.3(0.28–0.43) <0.001
 < 16 447(5.8) 85(9.8) 0.6(0.44–0.72) <0.001 48(5.6) 84(9.8) 0.5(0.38–0.80) 0.001
 16–24 545(7.0) 155(18.0) 0.3(0.29–0.42) <0.001 83(9.7) 154(18.0) 0.5(0.37–0.65) <0.001
 ≥ 25 299(3.9) 98(11.4) 0.3(0.25–0.40) <0.001 25(2.9) 98(11.4) 0.2(0.15–0.37) <0.001
 ICU LOS (days) 6.9 ± 8.3 7.6 ± 9.0 0.172 6.1 ± 6.8 7.6 ± 9.1 0.043
Mortality 83(1.1) 36(4.2) 0.2(0.17–0.37) <0.001 7(0.8) 36(4.2) 0.2(0.09–0.44) <0.001
  1. CI confidence interval, BMI body mass index, DM diabetes mellitus, HTN hypertension, CAD coronary artery disease, CHF congestive heart failure, CVA cerebral vascular accident, ESRD end-stage renal disease, BAC blood alcohol concentration, GCS Glasgow Coma Scale, AIS Abbreviated Injury Scale, ISS injury severity score, IQR interquartile range, LOS length of stay, ICU intensive care unit