Table 2.

Summary statistics for sleep, 24-hour activity rhythms, cognitive reserve, and time between\\ the measurements (N = 1,002)

Measurement
Sleep, mean (SD)
Total sleep time, min/night	376.4 (50.9)
Sleep efficiency, %	77.6 (7.8)
Sleep onset latency, min/night	17.3 (13.6)
Wake after sleep onset, min/night	55.6 (23.3)
24-hour activity rhythms
Interdaily stability, score, mean (SD)	0.74 (0.1)
Intradaily variability, score, mean (SD)	0.46 (0.1)
L5-onset, hour:min, median (IQR)	01 : 38 (00 : 57– 2 : 36)a
Cognitive reserve, score, mean (SD)	0 (1)*
Time between measurements, median (IQR)
Actigraphy and cognition, days	0 (56)
Actigraphy and MRI, days	47 (65)
MRI and cognition, days	56 (51)

^aMissing n = 9, *This variable was standardized. Abbreviations: SD, standard deviation, IQR, interquartile range.