Table 1.

Patient characteristics (n = 159,720)

Characteristic	All	Hemoglobin Variability Groupa						P Valueb
		L-L	I-I	H-H	L-I	I-H	L-H
Hemoglobin category (<11/11 to 12.5/>12.5)
Month 1	22.6/47.7/29.7	100/0/0	0/100/0	0/0/100	38.3/61.7/0	0/54.6/45.4	35.3/32.5/32.2	—
Month 2	21.5/48.8/29.8	100/0/0	0/100/0	0/0/100	41.0/59.0/0	0/51.8/48.2	31.3/38.5/30.2	—
Month 3	20.6/49.1/30.2	100/0/0	0/100/0	0/0/100	42.3/57.7/0	0/52.8/47.2	28.7/39.2/32.1	—
Month 4	19.9/48.4/31.8	100/0/0	0/100/0	0/0/100	42.4/57.6/0	0/52.5/47.5	26.7/37.7/35.6	—
Month 5	20.0/49.1/30.9	100/0/0	0/100/0	0/0/100	43.8/56.2/0	0/55.8/44.2	26.5/37.4/36.1	—
Month 6	19.2/47.4/33.4	100/0/0	0/100/0	0/0/100	39.2/60.8/0	0/55.3/44.7	26.5/31.6/41.9	—
Gender
male	51.3	54.0	54.1	56.3	51.0	52.7	49.5	<0.0001
female	48.7	46.0	45.9	43.7	49.0	47.3	50.6
Race
white	53.4	48.5	58.5	51.3	54.7	53.4	52.4	<0.0001
black	40.3	46.6	35.0	41.6	39.2	40.3	41.3
other	6.3	4.9	6.5	7.1	6.2	6.3	6.3
Age, years
<40	8.8	16.8	7.3	9.3	9.6	7.8	9.2	<0.0001
40 to 64	41.2	50.1	39.0	41.0	42.8	40.6	40.9
65 to 74	26.3	19.6	27.2	26.3	25.7	26.7	26.3
≥75	23.8	13.5	26.6	23.4	22.0	24.9	23.6
Cause of renal failure
diabetes	42.8	35.1	43.4	42.4	42.7	42.9	43.0	<0.0001
hypertension	29.8	27.3	28.4	30.4	28.5	30.5	30.0
other	27.4	37.6	28.2	27.3	28.8	26.7	27.0
Dialysis vintage, yr
<1	20.5	18.7	14.0	28.2	16.1	21.4	22.3	<0.0001
1 to <3	31.5	27.2	35.9	27.5	32.3	31.7	30.8
3 to <5	20.8	19.6	22.9	17.9	22.1	20.7	20.2
≥5	27.2	34.5	27.3	26.5	29.6	26.3	26.7

^aMonthly hemoglobin values were categorized as low (L, <11 g/dl), intermediate (I, 11 to 12.5 g/dl), and high (H, >12.5 g/dl); variability groups were classified on the basis of the lowest and highest categories seen in the 6-mo observation period. Values are percents.

^bχ² test.