Social Activity and Cognitive Functioning Over Time: A Coordinated Analysis of Four Longitudinal Studies

Table 1

OCTO-twin participant characteristics.

	Year of testing
Measure	Baseline (𝑛=524)	Year 2 (𝑛=424)	Year 4 (𝑛=326)	Year 6 (𝑛=245)	Year 8 (𝑛=175)
	M (SD)	M (SD)	M (SD)	M (SD)	M (SD)
Retention from previous testing (%)		82.9	76.7	76.2	72.8
Age	83.2 (2.9)	85.2 (2.8)	86.9 (2.5)	88.8 (2.5)	90.7 (2.4)
Education	7.2 (2.3)	7.3 (2.4)	7.3 (2.3)	7.2 (2.1)	7.2 (2.3)
Sex, female [𝑛 (%)]	365 (66)	299 (65)	233 (66)	193 (72)	146 (74)
Reasoning	11.6 (7.1)	11.6 (7.1)	11.5 (7.0)	10.2 (7.3)	10.2 (7.3)
Memory	9.6 (4.0)	9.5 (4.2)	9.5 (4.2)	9.1 (4.4)	9.1 (4.4)
Semantic knowledge	28.2 (11.1)	28.8 (11.1)	28.8 (11.1)	26.1 (11.4)	26.1 (11.4)
Social activity	3.0 (1.0)	3.0 (1.0)	3.1 (0.9)	2.8 (1.0)	2.8 (0.9)
Social activity change	—	−0.1 (1.0)	−0.0 (1.1)	−0.2 (1.1)	−0.4 (1.2)

M: mean, SD: standard deviation. The range for each measure with a defined upper limit is as follows: reasoning = 0–42, memory = 0–16, semantic knowledge = 0–44, and social activity = 0–4. Higher scores represent higher activity.