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Table 5 Incidence rate ratio (IRR) of the correlations between parachute injuries and other factors

From: Incidence and risk factors associated with injuries during static line parachute training in Royal Thai Army

FactorsCrude IRR95%CIAdjusted IRR1a95%CIAdjusted IRR2b95%CI
Type of aircraft
 Plane2.17****1.45–3.233.70***1.47–9.091.750.68–4.55
 Helicopter1.00Reference1.00Reference1.00Reference
Aircraft exit
 Side exit2.22****1.59–3.131.79***1.25–2.562.13****1.43–3.23
 Rear exit1.00Reference1.00Reference1.00Reference
Time of day
 Night0.690.44–1.072.81*1.07–7.412.190.81–5.90
 Day1.00Reference1.00Reference1.00Reference
Jump with equipment
 With equipment1.190.85–1.65  1.280.88–1.87
 Without1.00Reference  1.00Reference
Motion sickness
 Yes4.47****2.52–7.913.55****2.00–6.313.43****1.93–6.12
 No1.00Reference1.00Reference1.00Reference
Wind speed (knot) Each 1 knot increase in wind speed1.58****1.35–1.85  1.54****1.27–1.87
 ≥ 51.58***1.15–2.18    
 < 51.00Reference    
Temperature (°C)
Each 1 °C increase in temperature
1.18****1.07–1.31    
 ≥ 321.060.78–1.44    
 < 321.00Reference    
Rank
 NCO0.750.33–1.67    
 Cadet1.040.45–2.40    
 Officer1.00Reference    
Body mass index (kg/m2)
 ≥ 25.001.340.78–2.30    
 23.00–25.001.050.72–1.52    
 < 23.001.00Reference    
Age (years)
 ≥ 291.530.48–4.86    
 24–291.290.44–3.77    
 20–241.360.49–3.80    
 < 201.00Reference    
  1. IRR Incidence rate ratio
  2. * P< 0.05; **P< 0.01; ***P< 0.005; **** P<0.001
  3. aFactors included in the regression model are helicopter, rear exit, night jump and motion sickness
  4. bFactors included in the regression model are helicopter, rear exit, night jump, motion sickness, jump with equipment and high wind speed (assuming that wind speed and injuries have a linear correlation)