Prognostic implications of differences in forced vital capacity in black and white US adults: Findings from NHANES III with long-term mortality follow-up

Background: Because Forced Vital Capacity (FVC) is reduced in Black relative to White Americans of the same age, sex, and height, standard lung function prediction equations assign a lower normal range for Black patients. The prognostic implications of this race correction are uncertain. Methods: We analyzed 5,294 White and 3,743 Black participants age 20-80 in NHANES III, a nationally -representative US survey conducted 1988-94, which we linked to the National Death Index to assess mortality through December 31, 2015. We calculated the FVC-percent predicted among Black and White participants, first applying NHANES III White prediction equations to all persons, and then using standard race-specific prediction equations. We used Cox proportional hazard models to calculate the association between race and all-cause mortality without and with adjustment for FVC (using each FVC metric), smoking, socioeconomic factors, and comorbidities. Findings: Black participants' age-and sex-adjusted mortality was greater than White participants (HR 1.46; 95%CI:1.29, 1.65). With adjustment for FVC in liters (mean 3.7 L for Black participants, 4.3 L for White participants) or FVC percent-predicted using White equations for everyone, Black race was no longer independently predictive of higher mortality (HR similar to 1.0). When FVC-percent predicted was corrected for race, Black individuals again showed increased mortality hazard. Deaths attributed to chronic respiratory disease were infrequent for both Black and White individuals. Interpretation: Lower FVC in Black people is associated with elevated risk of all-cause mortality, challenging the standard assumption about race-based normal limits. Black-White disparities in FVC may reflect deleterious social/environmental exposures, not innate differences. (C) 2021 The Authors. Published by Elsevier Ltd.

Automated summary

This study found that lower FVC in Black individuals is associated with increased risk of all-cause mortality, challenging the standard assumption about race-based normal limits. The Black-White disparities in FVC may be attributed to social/environmental factors rather than innate differences.