Table 1.

Study characteristics, proportion dropped out and Cohen’s d difference in cognition between people who remained in the study and those who dropped out, by study

Study	Country	Age range	# waves used	Wave sample size range	Years between waves	Average age in waves used (95% CI)	Average proportion of all-inclusive dropout in each wave* (95% CI)	Cohen’s d† (95% CI)
Australian Longitudinal Study of Ageing	Australia	56+	2	87–436	2	87.9 (85 to 90.8)	0.41 (0.3 to 0.53)	0.4 (0.16 to 0.63)
Canberra Longitudinal Study	Australia	70+	3	209–631	4	82.8 (80.3 to 85.3)	0.41 (0.32 to 0.51)	0.51 (0.29 to 0.72)
Einstein Aging Study	USA	70+	17	223–568	1	80.8 (79 to 82.6)	0.31 (0.24 to 0.37)	0.29 (0.11 to 0.47)
English Longitudinal Study of Ageing	UK	50+	8	7898–10310	2	66.7 (64.7 to 68.7)	0.17 (0.12 to 0.23)	0.38 (0.19 to 0.56)
Health and Retirement Study	USA	50+	13	14 702–19682	2	68 (66.1 to 69.8)	0.14 (0.09 to 0.19)	0.46 (0.28 to 0.64)
Long Beach Longitudinal Study	USA	50+	4	396–1038	3	73.5 (71.1 to 75.8)	0.47 (0.38 to 0.56)	0.33 (0.13 to 0.53)
Mexican Health and Aging Study	Mexico	50+	4	11 653–14584	3	65 (62.6 to 67.3)	0.18 (0.11 to 0.26)	0.22 (0.02 to 0.42)
Swedish Adoption/Twin Study on Aging	Sweden	50+	5	247–328	3	70.2 (68 to 72.4)	0.15 (0.1 to 0.22)	0.45 (0.25 to 0.65)
Survey of Health, Ageing and Retirement in Europe	European countries and Israel	50+	4	35 899–74183	2	66.9 (64.6 to 69.3)	0.29 (0.22 to 0.38)	0.22 (0.01 to 0.42)
The Irish Longitudinal Study on Ageing	Ireland	50+	3	5715–7207	2	66.3 (63.8 to 68.9)	0.14 (0.08 to 0.21)	0.48 (0.27 to 0.7)
Overall average	–	–	6.3	–	2.4	72.8 (67.6 to 77.9)	0.26 (0.18 to 0.34)	0.37 (0.30 to 0.43)

*Includes dropout from all causes (death, refusal, etc) to provide a representation of the relative sizes of the dropout and non-dropout groups that were compared to examine differences in cognition.

†Difference in cognition tests performed in the prior wave between people who remained in the study and those who dropped out in the current wave.