Forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1) were measured at baseline and 3-year follow-up using standard spirometry.

• 用力肺活量（肺活量）和用力呼气容积在1秒（第一秒吐气量）进行测量，在基线和3年期的后续使用标准肺量。