Table 1.

Sample size and attrition across the 5 waves

	Wave 1 (1991– 1993)	Wave 2 (1993– 1995)	Wave 3 (1995– 1997)	Wave 4 (1997– 1999)	Wave 5 (1999– 2001)
Participation	417	339	274	211	167
Reason for attrition
Death		51	53	53	41
Refusal		24	12	9	3
Other reason		3	0	1	0