Table 1: OCTO-twin participant characteristics.

Year of testing
MeasureBaseline ( 𝑛 = 5 2 4 ) Year 2 ( 𝑛 = 4 2 4 )Year 4 ( 𝑛 = 3 2 6 )Year 6 ( 𝑛 = 2 4 5 )Year 8 ( 𝑛 = 1 7 5 )
M (SD)M (SD)M (SD)M (SD)M (SD)

Retention from previous testing (%)82.976.776.272.8
Age83.2 (2.9)85.2 (2.8)86.9 (2.5)88.8 (2.5)90.7 (2.4)
Education7.2 (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)
Reasoning11.6 (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 knowledge28.2 (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.