Trend and heterogeneity in forced vital capacity among Chinese students during 1985-2019: results from Chinese National Survey on Students' Constitution and Health.

Background: Forced vital capacity (FVC) reflects respiratory health, but the long-term trend and heterogeneity in FVC of Chinese students were understudied.

Methods: Data were from Chinese National Survey on Students' Constitution and Health 1985-2019. Super Imposition by Translation and Rotation model was used to draw FVC growth curves. Sex-, region-, and nationality-heterogeneity in FVC was evaluated. Spearman correlation and generalized additive model was used to reveal influencing factors for FVC.

Results: Compared to 1985, age at peak FVC velocity was 1.09, 3.17, 0.74, and 1.87 years earlier for urban male, urban female, rural male, and rural female in 2019, respectively. Peak FVC velocity first decreased and then increased during 1985-2019, only male rebounded to larger than 1985 level. FVC declined from 1985 to 2005 and then raised. Males consistently had higher FVC than females, with disparities increasing in the 13-15 age group. Urban students also had higher FVC than rural students. In 2019, FVC difference between 30 Chinese provinces and the national average showed four scenarios: consistently above national average; less than national average until age 18, then above; greater than national average until age 18, then this advantage reversed; less than national average in almost all the age. Most Chinese ethnic minority students had lower FVC levels compared to Han students. Spearman correlation and generalized additive model showed that age, sex, and height were the leading influencing factors of FVC, followed by socioeconomic and environmental factors.

Conclusions: Chinese students experienced advanced FVC spurt, and there was sex-, region- and nationality-heterogeneity in FVC. Routine measurement of FVC is necessary in less developed areas of China.