“…The main outcome of interest was FEV 1 and it has been the most widely reported index of lung function in the included studies. [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] Moreover, it allows the determination of the FEV / FVC ratio, which is used to detect the presence of airway obstruction and to diagnose lung diseases. All the included studies reported estimates for FEV 1 , either as mean values of volume, [12][13][14]16,17,20,21,23,25,26,28,30 mean difference, 15,18,19,22,24,27,31 or z-scores.…”