Table 1.

Characteristics of Participants in the Veterans With ALS and Lead Exposure Study, United States, 2003–2007

	All Participants				White Men Only
	Cases (n = 200)		Controls (n = 229)		Cases (n = 184)		Controls (n = 194)
	No.	%	No.	%	No.	%	No.	%
Age, yearsa	63.3 (34–83)		63.4 (34–84)		63.4 (34–83)		64.3 (34–84)
Gender
Men	196	98	216	94	184		194
Women	4	2	13	6	0		0
Race
White	187	94	205	90	184		194
Nonwhite	13	6	24	10	0		0
Cigarette smokingb
Ever	133	66	154	67	123	67	136	70
Never	62	31	75	33	56	30	58	30
Missing	5	2			5	3
Reviewed diagnosisb
Clinically definite ALS	31	16			29	16
Clinically probable ALS, laboratory supported	35	18			33	18
Clinically probable ALS	73	36			67	36
Clinically possible ALS	24	12			22	12
Progressive muscular atrophy	30	15			28	15
Primary lateral sclerosis	7	4			5	3
Site of onset
Bulbar	39	20			35	19
Spinal	161	80			149	81
Symptom onset to diagnosis
≤1 year	102	51			96	52
>1 year	98	49			88	48
Diagnosis to sample collection
≤2 years	159	80			144	78
>2 years	41	20			40	22

Abbreviation: ALS, amyotrophic lateral sclerosis.

^aValues are expressed as mean (range).

^bPercentages may not add to 100% because of rounding.