Table 1. Participants in each follow-up survey of the Beijing elderly.

	1992	……	1994	……	1997	……	2000
Invited (survivors of original cohort), no.	3257		2703		2002		1578
Dead between two interviews, no.		384		400		294
Missing (refused or moved from Interview area), no.		170		301		130
No. (elderly who participated in all surveys)	1578		1578		1578		1578