Table 1. Descriptive statistics of samples studied from HRS and ELSA (unweighted).

		Age		Cognition		Percent Female
Cohort	N	Mean	(s.d.)	Mean	(s.d.)
HRS92	9,794	55.5	(3.2)	10.8	(3.6)	52.9%
AHEAD	7,399	77.6	(5.9)	7.4	(3.9)	61.3%
CODA	2,301	70.6	(2.0)	9.4	(3.4)	59.1%
WB	2,061	53.2	(2.8)	11.4	(3.2)	45.9%
EBB	2,690	52.9	(1.7)	10.6	(3.2)	48.6%
All HRS	24,245	63.2	(11.4)	9.7	(3.9)	55.0%
ELSA	11,392	65.3	(10.4)	9.1	(3.9)	54.5%

Notes: Abbreviations are HRS (Health and Retirement Study), ELSA (English Longitudinal Study of Ageing, baseline interviews in 2003), HRS92 (first Health and Retirement Study cohort introduced in 1992, age-eligibles are born 1931-41), AHEAD (second Health and Retirement Study cohort introduced in 1993 as Asset and Health Dynamics of the Oldest-Old, age-eligibles born before 1924), CODA (Children of Depression Age; third Health and Retirement Study cohort introduced in 1998, age-eligibles born 1924-30), WB (War Babies; fourth Health and Retirement Study cohort introduced in 1998, age-eligibles born 1942-47), EBB (Early Baby Boomers; fifth Health and Retirement Study cohort introduced in 2004, age-eligibles born 1948-53). Cognition is measured by the sum of words recalled immediately and after delay from a list of ten words.