Table 4.

Mean difference (mean d.) between lung function parameters in different years and the pre-employment year.

Years	FVC			FEV1			FEV1/FVC			PEF
	Mean ± SD	Mean d.	p-value∗	Mean ± SD	Mean d.	p-value∗	Mean ± SD	Mean d.	p-value∗	Mean ± SD	Mean d.	p-value∗
2009∗∗	99.51 ± 12.90			99.62 ± 12.66			100.3 ± 8.1			101.3 ± 16.6
2011	101.42 ± 12.33	3.2 ± 0.9	0.001	100.42 ± 12.71	1.9 ± 0.8	0.02	99.13 ± 6.74	−1.6 ± 0.5	0.004	100.30 ± 14.71	−0.8 ± 1.1	0.48
2013	96.41 ± 12.14	−1.5 ± 1.1	0.1	97.14 ± 11.31	−2.1 ± 0.9	0.03	100.92 ± 6.15	−0.7 ± 0.5	0.1	99.37 ± 13.82	−2.7 ± 1.2	0.02
2015	95.54 ± 14.27	−2.3 ± 1.4	0.1	95.55 ± 12.95	−3.2 ± 1.2	0.008	100.41 ± 7.49	−0.9 ± 0.7	0.1	100.77 ± 16.45	0.6 ± 1.3	0.6
2019	93.22 ± 7.47	−7.3 ± 2.2	0.002	91.65 ± 8.05	−8.5 ± 1.9	<0.001	98.45 ± 6.28	−1.8 ± 1.5	0.2	98.33 ± 9.41	−4.2 ± 2.8	0.1

^∗Paired t-test.

^∗∗Pre-employment year. FVC: forced vital capacity; FEV1: forced expiratory volume in the first second; PEF: peak expiratory flow.