Forced Vital Capacity and Quality of Life: BOLD Study Cross-Sectional Analysis

Abstract

Background: A low forced vital capacity (FVC) is associated with all-cause mortality even among people without respiratory symptoms. The effect it has on quality of life (QoL) is less clear.

Aims: To assess the relationship between FVC and QoL in the multinational BOLD (Burden of Obstructive Lung Disease) study and explore differences by country gross national income.

Methods: We used data from 27,653 adults (≥40 years), from 41 sites, participating in the BOLD study who had provided acceptable post-bronchodilator spirometry measurements and information on the quality of their mental and physical health. To assess the association between FVC and QoL within each site, we used linear regression models, adjusted for potential confounders. Effect estimates from all sites were then combined using meta‑analysis.

Results: We found a positive association between post-bronchodilator FVC and QoL. In particular, for each litre increase in FVC, the mental health score increased by 0.49 (β-coef.=0.49, 95%CI 0.32-0.66). Similarly, higher FVC was associated with higher physical health score (β-coef.=1.47. 95%CI 1.17-1.77). The association with physical health was stronger and less heterogeneous in high-income sites (β-coef.=1.98, 95%CI 1.65-2.31, I2=25.4%) compared to low- and middle-income sites (β-coef.=1.15, 95%CI 0.77-1.53, I²=71.2%).

Conclusions: Our findings suggest that people with larger lungs are more likely to have better QoL. Although the mechanism underlying this association is unclear, it is likely that interventions to improve lung development during childhood and to maintain good lung function during adulthood would help to secure a better QoL.