On the Temporal Relationships between Lung Function and Somatic Growth

Abstract

A sample population of healthy nonsmoking male (n = 416) and female (n = 608) subjects derived from all non-Hispanic white subjects 5 to 60 yr of age enrolled in the Tucson Epidemiological Study of Airway Obstructive Disease was studied to evaluate the temporal relationships between various pulmonary function measures and somatic growth. Pulmonary function measures derived from the maximal expiratory flow volume (MEFV) curve included FVC, FEV1, maximal expiratory flow after 50% of vital capacity had been expired (.ovrhdot.V max50) and maximal midexpiratory flow (FEF25-75). The lung function and somatic growth longitudinal data were characterzed by a nonparametric polynomial smoothing spline model. This procedure yields an optimal fitted curve though the data, and estimate of the growth velocity curve, and 95% confidence bands. Temporal relationships between the fitted growth curves were determined examining the ages at which the growth velocity peaks (GVP) occur. In addition, the age of growth cessation was estimated using lower limits of the 95% confidence bands of each velocity curve. The results indicate that the point estimates of the somatic GVPs precede all peak lung function measurements derived from the MEFV curve in both males and females. The only statically significant difference between when the GVPs for somatic growth and functional lung growth occurred was for FEV1 and FEF25-75 in males, though similar trends were apparent in all other variables, suggesting that the timing of maximun body growth velocity precedes that the maximal lung functional growth and that the early growth spurt in females includes the lungs. For example the cessation of lung growth estimates, we found that the FEV1 slope could not be distinguished from zero at 19.82 yr of age for males and 17.88 yr for females, with similar values for FVC, .ovrhdot.V max50 and FEF25-75. Additional regression analysis was alos applied to adult subjects to determine the age at which lung function increases its rate of decline; this was approximately 43 yr of age for males and 37 yr for females.