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, FEV1/FVC, V50, V25, V50/FVC, FRC, and delta N2 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 V50 and V25, indicating that these pulmonary function variables are influenced predominantly by genetic factors in adulthood. These results indicate that small airway dynamics, in terms of V50 and V25, 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.