Table 3.

Disc grade by donor age group and disc level. (A) mean and standard error of the mean, and (B) counts. (C) Results of random effects linear regression model.

A. Mean ± Standard Error of T2 value of the NP
Age	L1–2	L2–3	L3–4	L4–5	Total
<40	2.25 ± 0.25	1.75 ± 0.25	1.75 ± 0.48	2.25 ± 0.25	2.00 ± 0.16
40–49	2.75 ± 0.25	2.00 ± 0.00	2.25 ± 0.48	2.25 ± 0.25	2.31 ± 0.15
50–59	3.00 ± 0.14	2.80 ± 0.15	2.63 ± 0.13	3.00 ± 0.12	2.86 ± 0.07
60–69	2.92 ± 0.19	2.71 ± 0.19	2.75 ± 0.14	3.21 ± 0.16	2.90 ± 0.09
70+	3.00 ± 0.24	3.00 ± 0.00	3.00 ± 0.29	3.22 ± 0.15	3.06 ± 0.10
all ages	2.92 ± 0.10	2.69 ± 0.10	2.65 ± 0.09	3.01 ± 0.08	2.82 ± 0.05

B. Counts
Age	L1–2	L2–3	L3–4	L4–5	Total
<40	4	4	4	4	16
40–49	4	4	4	4	16
50–59	30	30	30	30	120
60–69	24	24	24	24	96
70+	9	9	9	9	36
All Ages	71	71	71	71	284

C. Linear regression: Disc grade as function of disc level, age, and sex.
Factors	Value	Std. Error	DF	t-value	p-value
Intercept	1.711	0.385	210	4.442	<0.001
L1–2	−0.099	0.103	210	−0.958	0.339
L2–3	−0.324	0.103	210	−3.149	0.002
L3–4	−0.366	0.103	210	−3.560	<0.001
(Ref. L4–5)
Age	0.024	0.006	68	3.669	<0.001
Sex (M)	−0.095	0.154	68	−0.616	0.540