Table 2.

Linear mixed models for 4 kHz HTL and DPOAE*

4 kHz HTL	Phases 1 and 2		Phase 2 only
	Estimate (SE)	p Value	Estimate (SE)	p Value
Fixed effects
Phase 2	2.22 (0.550)	<0.001	–
Age (>30 years)	3.03 (0.901)	0.001	6.90 (1.66)	<0.001
Gender (male)	2.05 (1.05)	0.050	0.883 (2.10)	>0.2
HTL at baseline (ref <10)
10–20	7.50 (0.788)	<0.001	6.63 (1.37)	<0.001
>20	30.2 (1.09)	<0.001	31.0 (1.91)	<0.001
Years since BL (years)	0.025 (0.139)	>0.2	0.648 (0.53)	0.010
Noise exposure × years (dB×years)	0.023 (0.008)	0.003	0.034 (0.013)	0.011
Random effects
Subject: random intercept SD	4.78 (0.481)		9.57 (1.45)
Subject: random slope SD	0.735 (0.54)		1.32 (0.174)
Subject: intercept–slope corr.	0.024 (0.114)		−0.688 (0.092)
Ear: random intercept SD	6.46 (0.302)		7.21 (0.472)
Residual SD	4.20 (0.065)		3.75 (0.112)

4 kHz DPOAE (40 dB)	Phases 1 and 2		Phase 2 only
	Estimate (SE)	p Value	Estimate (SE)	p Value
Fixed effects
Phase 2	−6.64 (0.762)	<0.001	–
Age (>30 years)	−2.45 (0.737)	<0.001	−2.56 (1.12)	0.023
Gender (male)	−3.61 (0.875)	<0.001	−3.24 (1.46)	0.026
HTL at BL (ref <10)
10–20	−3.83 (0.531)	<0.001	−3.13 (0.993)	<0.002
>20	−8.79 (0.778)	<0.001	−5.00 (1.34)	<0.001
Years since BL (years)	0.059 (0.143)	>0.2	0.516 (0.221)	0.020
Noise exposure × years (dB×years)	−0.011 (0.006)	0.083	−0.020 (0.008)	0.026
Random effects
Subject: random intercept SD	5.23 (0.338)		9.42 (2.31)
Subject: random slope SD	0.450 (0.063)		0.762 (0.369)
Subject: intercept–slope corr.	−0.375 (0.119)		−0.914 (0.067)
Ear: random intercept SD	2.60 (0.262)		4.75 (0.437)
Residual SD	6.13 (0.095)		5.68 (0.167)

^*Effect estimates in dB per unit change of each predictor.