Pattern of Genetic Influence on Pulmonary Function

Whether genetic factors influence small airway function and lung volume was examined in 20 adolescent (mean age, 16.2±SD 1.1 years) monozygotic twin pairs, 11 adolescent (mean age, 16.7±0.7 years) dizygotic twin pairs, and 20 adult (mean age, 38.7±9.3 years) monozygotic twin pairs. Within-pair variances of adolescent dizygotic twins for height, FVC, FEV 1 /FVC, V ˙ 50 , V ˙ 25 , V ˙ 50 /FVC, FRC, and ΔN 2 were significantly larger than those of adolescent monozygotic twins, indicating that these pulmonary function variables are influenced predominantly by genetic factors in adolescence. Within-pair variances of adult monozygotic twins were similar to those of adolescent monozygotic twins in terms of V ˙ 50 and V ˙ 25 , indicating that these pulmonary function variables are influenced predominantly by genetic factors in adulthood. These results indicate that small airway dynamics, in terms of V M and V M , are influenced in larger part by genetic factors in adolescence as well as adulthood, whereas lung volumes in terms of FRC and FVC are controlled by genetics only in adolescence.