Fig. 3.

Early risk factors for COPD and smoking exposure in different stages of life in individuals with supernormal lung function in the general population. Based on the Copenhagen General Population Study. *P <0·05 for comparison with normal lung function using Pearson's chi-squared or Fisher's exact test. †P <0·05 for comparison with below normal lung function using Pearson's chi-squared or Fisher's exact test. ‡Information on birthweight was available on a subset of 3588 individuals. COPD=chronic obstructive pulmonary disease.