TABLE 1.

Characteristics of the study cohort (US Veterans Affairs): White and black male veterans with at least one hospital admission between July 1, 1969 and September 30, 1996, who were followed more than one year.^a

Characteristics	Whites		Blacks
	Non-WM	WM	Non-WM	WM
No. of persons	3,668,667	316	832,250	45
Mean age at study entrya	51.1	61.0	47.7	53.2
Years of follow-up (mean)b	11.7	7.4	11.9	7.5
Person-years at riskb	42,759,826	2,352	9,888,663	338
Median number of hospital visits	3	4c	3	4c

^aAge at first discharge record for inpatient hospitalization at Veterans Affairs hospitals between July 1, 1969 and September 30, 1996.

^bFollow-up started one year after the first hospital visit.

^cIncludes visits up to the exit date.

Abbreviations: WM=Waldenström’s macroglobulinemia.