Sensitive Tests Are Poor Predictors of the Decline in Forced Expiratory Volume in One Second in Middle-aged Smokers

In 1978, we studied 3 groups of steelworkers 45 to 55 yr of age who were all smokers: “obstructive” smokers (OS) with a FEV1/VC less than 66.6% (59.8% in average) (n = 37), smokers with “small airways disease” (SAD) and an abnormal closing capacity and/or slope of phase III (ΔN2) but normal FEV1/VC (n = 32), and “resistant” smokers (RS) with normal functional indices (n = 36). Smokers with SAD had a lower (p 0.05). In all 3 groups, ΔN2 increased (p < 0.001) from 0.77 to 1.30% N2/L in RS, 1.41 to 2.43% N2/L in smokers with SAD, and 2.22 to 4.20% N2/L in OS. A multivariate analysis showed that the initial N2 explained about 30% (p < 0.001) of the decline in FEV1 in OS, but only 10% (p < 0....