Table 3.

Rank correlations (r_s) of age and sleep-related variables.

	SQI	MSD	MSDc	Smoking	Caffeine
Age [years]	−0.04	−0.13*	−0.01	−0.40***	−0.07
Sleep quality index SQI [0–2]	–	−0.27***	−0.34***	−0.03	−0.04
Mean sleep duration MSD [h]		–	+0.92***	−0.03	+0.06
MSD categories [1–5]			–	−0.11	+0.02
Smoking status [0–2]				–	+0.35***

SQI, sleep quality index (non-restorative sleep); MSD, mean sleep duration; MSDc, categories of sleep duration recommendations;

^*P<0.05.

^***P<0.001.