Table 2

Regression coefficients for adjusted lung function indices for new starters who were 18 years or older at the first sets of tests

	FEV₁ (l)		FVC (l)		FEV₁/FVC (%)		FEF_25–75% (l/s)
	Coefficient	p value	Coefficient	p value	Coefficient	p value	Coefficient	p value
*Limits of 95% CI for the parameter.
†FEF_25–75% was measured after January 1983, so the observation number is smaller than that for FEV₁, FVC, and FEV₁/FVC.
Intercept	3.58 (3.43 to 3.73)*	0.0001	4.27 (4.10 to 4.43)	0.0001	83.5 (81.4 to 85.7)	0.0001	4.38 (3.76 to 5.00)	0.0001

Ex-smokers	−0.030 (−0.278 to 0.218)	0.813	0.129 (−0.149 to 0.407)	0.366	−3.26 (−6.79 to 0.28)	0.0731	−0.484 (−1.23 to 0.27)	0.217

Duration of smoking for ex-smokers (years)	0.00336 (−0.0196 to 0.0263)	0.776	−0.00728 (−0.0330 to 0.0184)	0.581	0.173 (−0.153 to 0.500)	0.302	0.0100 (−0.0762 to 0.0962)	0.824

Current smokers	−0.0631 (−0.165 to 0.039)	0.230	0.0190 (−0.095 to 0.133)	0.747	−1.56 (−3.02 to −0.11)	0.0366	−0.0392 (−0.431 to 0.353)	0.848

Pack-years for current smokers	0.00113 (−0.00412 to 0.00636)	0.676	0.00305 (−0.00282 to 0.00891)	0.313	−0.0694 (−0.144 to 0.005)	0.0705	−0.0370 (−0.0618 to −0.0122)	0.0046

Operation	−0.0125 (−0.153 to 0.128)	0.863	0.0731 (−0.084 to 0.230)	0.365	−1.46 (−3.45 to 0.541)	0.156	−0.479 (−1.06 to 0.101)	0.115

Maintenance	0.0154 (−0.152 to 0.183)	0.858	0.0523 (−0.135 to 0.240)	0.587	−0.669 (−3.05 to 1.71)	0.585	−0.523 (−1.17 to 0.125)	0.123

Electricity	−0.0145 (−0.240 to 0.211)	0.900	−0.0252 (−0.278 to 0.228)	0.846	−0.298 (−3.51 to 2.91)	0.857	0.0456 (−0.99 to 1.08)	0.933

R square	0.0035		0.0054		0.0231		0.0647
No. of observations†	613		613		613		202