Rapidly decreasing forced expiratory volume in one second or vital capacity and development of chronic airflow obstruction.

In a prospective study of 2,406 members of the Belgian Air Force, followed for 3 to 15 yr, 325 demonstrated a yearly decline in FEV1 and/or in vital capacity (VC) that was significantly faster than that expected in healthy nonsmokers. Such rapid declines were met more frequently in heavy smokers and in subjects with a reduced FEV1 or VC. There was no clear-cut association between rapid declines and a history of respiratory diseases. It may be predicted, if the rates of declines do not vary with aging, that about 0.5% of nonsmokers and 4% of heavy smokers in the investigated population will reach disabling airway obstruction (FEV1 of 1.2 L or less) at 65 yr of age. At least 6 to 8 yr of follow-up are required to appreciate with precision the rates of declines in FEV1 or in VC.