Table 2.

Principal Component Analyses of Sleep Characteristics

	PC1–sleep fragmentation 40.9% of the variance	PC2–phase delay 21.9% of the variance	PC3–hypersomnia 19.9% of the variance
Time of sleep midpoint	0.039	0.978	0.171
Time of sleep onset	0.018	0.944	−0.311
Time of morning awakening	0.051	0.82	0.558
Time in bed	0.289	0.068	0.905
Activity count per min	0.832	0.031	−0.029
Sleep onset latency	0.511	0.277	−0.075
Sleep efficiency	−0.868	−0.069	0.244
Wake after sleep onset	0.915	−0.061	0.236
Sleep duration	−0.244	0.015	0.963
Sleep proportion	−0.956	0.07	−0.007
Number of sleep bouts	0.734	−0.025	0.293
Fragmentation index	0.877	0.081	−0.009

PC, principal component; bold values represent those that loaded > 0.5 and contributed the most to the component.