Current and ex-smokers had lower mean exercise capacity compared with never smokers: 90 [standard deviation (SD) 10] % predicted,91 (SD 12) % predicted and 100 (SD 13) % predicted distance on 6MWT, respectively [mean differences −9.8%, 95% confidence intervals(CI) −17.8 to −1.8 and −9.1%, 95% CI −15.4 to −2.7, respectively; P < 0.05 for both].