Trends and Distributional Characteristics of Forced Vital Capacity and Forced Vital Capacity Adjusted for Weight Among Chinese Children and Adolescents Over the Three Decades

Abstract

Background: To assess trends and distributional characteristics of forced vital capacity (FVC) and vital capacity index (VCI) (a measure of FVC adjusted for weight) among Chinese children and adolescents aged 7-18 years from 1985 to 2019.

Methods: FVC and VCI data for Chinese children and adolescents were obtained from the Chinese National Surveillance on Students’ Constitution and Health surveys in 1985, 1995, 2000, 2005, 2010, 2014 and 2019. VCI (ml/kg) = FVC (ml)/weight (kg). Trends were estimated by sample-weighted regressions with post-stratification population-weighted procedures. The trends in the distributional characteristics were visually described.

Results: For the total population, FVC improved by 78.7 ml (95% confidence interval: -203.3 to 360.7 ml) or 0.12 effect size (ES) (-0.42 to 0.66 ES), which was a negligible improvement. VCI decreased by 11.5 ml/kg (4.8 to 18.3 ml/kg) or 0.84 ES (0.34 to 1.34 ES), which was a large decrease from 1985 to 2019. The sex, residence, and age-stratified VCI both experienced significant moderate to large decreases. Stratified by period, the FVC and VCI decreased dramatically until the 21st century, and the decrease stabilized from 2000 to 2010 and thereafter improved. FVC decreased in the lower percentile and increased in the higher percentile. For the VCI, the larger the percentile was, the smaller the decrease was. 

Conclusion: Absolute levels of lung function among Chinese children and adolescents have stabilized over the past three decades, but relative levels of lung function have declined significantly. The government should implement health promotion programs to improve respiratory health.