Table 1.

General characteristics of the study population

	Men						Women
	Lumbar disc herniation (n = 286)		Lumbar disc narrowing (n = 145)		Control subjects (n = 453)		Lumbar disc herniation (n = 278)		Lumbar disc narrowing (n = 206)		Control subjects (n = 448)
	N	%	N	%	N	%	N	%	N	%	N	%
Clinical symptoms in cases
Radiculopathy with motor/sensory deficit	157	54.9	45	31.0			137	49.3	52	25.2
Radiculopathy with sensory (and no motor) deficit	128	44.8	33	22.8			138	49.6	40	19.4
Radiculopathy with motor or sensory deficit or both, not further classified	1	0.3	1	0.7			3	1.1	2	1.0
Local lumbar syndrome	-	-	66	45.5			-	-	112	54.4
Age at diagnosis/interview, years
Less than 35	27	9.4	9	6.2	84	18.5	51	18.3	4	1.9	77	17.2
35 to less than 45	91	31.8	20	13.8	119	26.3	71	25.5	27	13.1	137	30.6
45 to less than 55	73	25.5	31	21.4	97	21.4	72	25.9	54	26.2	109	24.3
55 to less than 65	61	21.3	51	35.2	104	23.0	58	20.9	78	37.9	94	21.0
65 or more	34	11.9	34	23.4	49	10.8	26	9.4	43	20.9	31	6.9
Mean (standard deviation)	48.7 (11.1)		55.0 (10.7)		47.3 (12.6)		47.1 (11.8)		56.0 (9.8)		46.4 (11.8)
Cumulative lumbar workload, MNha
Less than 1.59	19	6.6	7	4.8	68	15.0	98	35.3	62	30.1	232	51.8
1.59 to less than 13.26	75	26.2	37	25.5	179	39.5	82	29.5	58	28.2	121	27.0
13.26 or more	192	67.1	101	69.7	206	45.5	98	35.3	86	41.7	95	21.2
Educational level
Graduated from high school	74	25.9	26	17.9	182	40.2	64	23.0	27	13.1	145	32.4
Secondary school level	83	29.0	32	22.1	125	27.6	101	36.3	59	28.6	173	38.6
Elementary level/no graduation	127	44.7	87	60.0	146	32.2	112	40.3	119	57.8	129	28.8
Unknown	2	0.7	-	-	-	-	1	0.4	1	0.5	1	0.2

^aCumulative lumbar workload refers to manual materials handling or intensive-load postures or both. MNh, meganewton-hours.