Are race and sex differences in lung function explained by frame size? The CARDIA Study.

Using the CARDIA cohort of 20- to 32-yr-old black and white men and women, FVC and FEV1 were standardized for standing height, sitting height, leg height, elbow breadth, and biacromial diameter in such a way that the standardized lung function showed minimal statistical dependence on these measures of frame size. Race and sex differences in lung function have been reported even after adjustment for height; however, these differences might depend on aspects of frame size other than height. We found that within this age group height2 provided robust standardization for FVC and FEV1 for all race and sex strata of the population. Height explained approximately 40% of the variance of FVC and FEV1 in whites, 30% in black women, and 20% in black men. In black men only, standardization for the combination of sitting height, leg height, elbow breadth, and biacromial diameter improved explained variance to nearly 40% for FVC and nearly 30% for FEV1. After standardization for height, FVC and FEV1 were found to be 14 to 19% higher in whites than in blacks, and in men than in women. Standardization of FVC and FEV1 for sitting height, leg height, elbow breadth, and biacromial diameter combined reduced these differences to 13-16%. Thus, race and sex differences in lung function exist even after detailed adjustment for frame size.