In white patients, the core-peel difference was significantly greater in the lung apex but not at the mid and basilar lung regions than in the African-American patients. In Figure 4, the frequency distribution of the core-peel percentage of emphysema differences are plotted for the whole lung, lung apex, and lung base. Note that the two frequency distributions for the apical lung are skewed in opposite directions for African-American vs white patients. No differences were noted for mild-to-moderate emphysema regions between the two groups when — 910 HU and — 850 HU were assumed as cutoffs. in detail
Our data show that African-American patients with advanced emphysema presented with impairment comparable to white patients as identified by lung function, exercise, and quality of life measures, and at a younger age despite smoking less. Each gender within the two racial groups was as affected as its counterpart; African-American women were not less severely sick than white women. However, when matched with respect to age, height, smoking, and pulmonary function, African-American patients demonstrated less severe emphysema measured by quantitative CT analysis, especially in the apical lung core, vs white patients. Notably, the enrollment rate of African Americans was much less than that of whites when viewed with respect to prior reports of emphysema prevalence. Traditionally, COPD is thought to be a disease of the white population, and the African Americans have been described as “protected” against developing emphysema. The prevalence rates of emphysema based on large surveys have consistently revealed a large gap between African Americans and whites. However, as yet the major determinant of the observed difference in prevalence is unclear. Differences in acquired exposures (smoking behavior, environmental exposure, infections, dietary intake), genetic susceptibility, or sampling biases are all possibilities.
Figure 4. Race-based core — peel percentage of emphysema differences. Frequency histograms (occurrence in the population) of core — peel differences in percentage emphysema obtained from the 34 matched-pair CT analysis (white patients on solid line). The panels demonstrate histograms for the whole lung (left, A), for the upper lung region (center, B), and for the lower lung region (right, C). Note the curve skewness that is opposite for white vs African-American patients in the apical lung region (center, B), serving to significantly separate the mean and medians of the two populations (p = 0.02).