Table 2

Univariate analysis for decline in FEV₁ over 36 months >9%

Parameter	Relative risk	p value	95% CI for risk ratio
BMI, body mass index; V˙O₂, oxygen consumption; V˙_E, minute ventilation; ΔP_ETCO₂,[(change in P_ETCO₂ to peak exercise) + (change in P_ETCO₂ from peak to termination of exercise)].
*:ΔP_ET CO₂ ⩾2 mm Hg in CO₂R and ΔP_ET CO₂ <2 mm Hg in CO₂NR.
Age (years)	1.00	0.78	0.98 to 1.08
Female	1.23	0.41	0.37 to 1.78
BMI (kg/m²)	0.96	0.61	0.43 to 1.14
V˙O₂ peak (ml/kg/min)	0.78	0.16	0.51 to 0.92
V˙_E peak (l/min)	0.85	0.28	0.66 to 0.96
FEV₁ at start (%)	0.92	0.18	0.81 to 1.05
ΔP_ET CO₂*(mm Hg)	5.81	0.0005	4.20 to 7.18