Table 4. Hearing thresholds as absolute values and Z-scores (with 95% CI): 25 year follow up (n = 9, mean age 46.1, SD 2.3 years). Statistically significant values have been marked with an asterisk. * P < 0.05, ** P < 0.01, *** P < 0.001 .

Frequency	Left		Right
	dB (95% CI) delta	Z-score (95% CI) delta	dB (95% CI) delta	Z-score (95% CI) delta
250 Hz	6.1 (-2.5–14.7) +2.4	0.88 (-0.99–0.88) +0.65	5.6 (-1.7–12.9) +1.2	0.87 (-0.99–2.73) +0.43
500 Hz	1.7 (-5.8–9.2) -5.3	0.28 (-1.59–0.28) -1.16	2.2 (-3.5–7.9) -3.40	0.03 (-1.22–1.28) -0.96*
1 Hz	5 (-3.2–13.2) -0.1	0.64 (-1.35–0.64) -0.6	2.8 (- 2.9–8.5) -3.70	0.15 (-1–1.3) -1.13*
2 Hz	5 (-6.2–16.2) -1.8	0.22 (-1.47–0.22) -1.52**	2.2 (- 4.9–9.3) -4.40	-0.34 (-1.79–1.11) -1.82***
3 Hz	3.9 (-5.3–13.1) -0.7	0.95 (-1.37–0.95) -1.45**	0 (-7.1–7.1) -1.3	-0.19 (-2.07–1.69) -1.32*
4 Hz	12.2 (1.3–23.1) +1.9	0.43 (-1.51–0.43) -1.75**	6.7 (-8.1–21.5) -0.6	0.16 (-1.94–2.26) -1.83**
6 Hz	19.4 (7.3–31.5) +11.0 *	0.8 (-0.73–0.8) -0.68	15.1 (6.3–23.9) +4.60	0.64 (-0.68–1.96) -1.6**
8 Hz	11.7 (-1.6–25) +4.4	-0.1 (-1.54–1.34) -1.11	6.1 (-4.1–16.3) -0.9	-0.54 (-1.85–0.77) -1.79**