Lung function decline and incidence of chronic obstructive pulmonary disease in participants with spirometry-defined small airway dysfunction: a 15-year prospective cohort study in China

Table 2 Annual rate of decline in lung function in participants with pre-bronchodilator small airway dysfunction and those without small airway dysfunction*

Variable	Pre-BD SAD		Unadjusted		Adjusted
Variable	Yes (N = 1419)	No (N = 3261)	Mean Difference (95% CI)	P Value	Mean Difference (95% CI) †	P Value †
Pre-BD lung function
FEV₁ (ml/year)	25.8 ± 1.2	27.6 ± 0.8	−1.7 (−4.5 to 1.1)	0.229	−1.6 (−4.1 to 0.9)	0.216
FEV₁ of predicted value (%/year)	0.31 ± 0.05	0.20 ± 0.03	0.11 (−0.01 to 0.22)	0.072	0.12 (0.01 to 0.23)	0.023
FEV₁ Z-score	0.025 ± 0.005	0.016 ± 0.003	0.009 (−0.002 to 0.020)	0.106	0.012 (0.002 to 0.021)	0.021
FVC (ml/year)	32.8 ± 1.8	16.8 ± 1.1	15.9 (11.7 to 20.2)	< 0.001	18.5 (14.7 to 22.3)	< 0.001
FVC of predicted value (%/year)	0.47 ± 0.06	−0.10 ± 0.04	0.57 (0.43 to 0.70)	< 0.001	0.67 (0.54 to 0.80)	< 0.001
FVC Z-score	0.032 ± 0.004	−0.012 ± 0.003	0.044 (0.034 to 0.054)	< 0.001	0.056 (0.045 to 0.068)	< 0.001

Plus–minus values are means ± standard error
BD = bronchodilator; SAD = small airway dysfunction; CI = confidence interval; FEV₁ = forced expiratory volume in one second; FVC = forced vital capacity; MMEF = maximal mid-expiratory flow; FEF50 = forced expiratory flow 50%; FEF75 = forced expiratory flow 75%
^* A random-effects model was adopted to evaluate the annual decline in lung function
^† Adjusted by age, sex, body mass index, smoking status, smoking index, family history of respiratory diseases, biomass exposure, occupational exposure history, and individual pre-bronchodilator spirometric values at baseline (FEV₁, FEV₁ of predicted value, FEV₁ Z-score, FVC, FVC of predicted value, and FVC Z-score)

ISSN: 1465-993X