Heritability estimates of pulmonary function.

To test the hypothesis that there is genetic control of pulmonary function parameters independent of that influencing height, we evaluated 74 pairs of asymptomatic, nonsmoking twins. FVC, FEV1, FEF25-75%, TLCsb, RVsb, Dsb, and D/VA were measured. Pulmonary function indices were adjusted for height using simple linear regression. Mean intrapair differences (unadjusted and adjusted for height) were compared using t tests of independent samples. Within pair, Holzinger's, and Falconer's heritability estimates were calculated using height-adjusted residual values. When total variances of a function parameter were statistically different between monozygotes and dizygotes, the among component heritability estimate was calculated and used as the best indicator of heritability. Following adjustment for height, no measure of pulmonary function which satisfied the requirements of the analysis was found to be significantly heritable.