Lung function changes as a reflection of tissue aging in young adults.

We studied 198 healthy young men and women 17 to 40 years of age, 110 blacks and 88 whites, all current non-smokers, with a view to identifying the changes, if any, consistent with lung tissue aging. Measurements were made of the maximal expiratory flow-volume (MEFV) curves (from which were derived forced vital capacity (FVC) and flow rates (Vmax) at 75%, 50% and 25% of expired VC), and transfer factor for carbon monoxide (TL). To describe aging trends, results were corrected for height differences and analysed by sex and race for five age groups. Certain changes (e.g. the age-related increase in FVC in men in the early 20's and decrease in the late 20's in both men and women) may be accounted for by changes in respiratory muscle force and/or increasing weight; in addition, the changes in FVC itself (used as the reference lung volume for reading flow rates off the MEFV curves) may have accounted in part for the age-related changes in Vmax at 75% and 50% VC. Likewise, increasing weight by influencing lung emptying may have contributed to the decrease in the diffusion constant in women. Only the age-related decline in Vmax at 25% VC (seen in women of both races and starting in the early 20's) could not be explained by the above factors, and may therefore reflect tissue aging.