Table 2.

Descriptive statistics and bivariate correlations among study variables.

Variable	M (SD)	Age	Sexa	Chronic disease historyb	Altitude of current residence	First-time high-altitude exposureb	Cumulative high-altitude residence	Oxygen supplementation frequency	Oxygen supplementation duration per session	Frequency of returning to low-altitude areas	Sleep difficulties
Age	24.68 (3.72)	–
Sexa	–	−0.03	–
Chronic disease historyb	–	0.20***	−0.03	–
Altitude of current residence	3.07 (0.45)	0.02	0.02	0.01	–
First-time high-altitude exposureb	–	−0.54***	0.03	−0.13***	−0.02	–
Cumulative high-altitude residence	3.94 (1.21)	0.40***	−0.02	0.16***	0.23***	−0.53***	–
Oxygen supplementation frequency	3.61 (1.44)	0.02	−0.12***	−0.09***	−0.10***	−0.04	−0.08**	–
Oxygen supplementation duration per session	3.02 (1.05)	0.10***	−0.09**	−0.02	−0.09**	−0.03	−0.05	0.45***	–
Frequency of returning to low-altitude areas	1.59 (0.70)	0.32***	−0.02	0.08**	0.03	−0.42***	0.34***	0.00	0.04	–
Sleep difficulties	3.02 (3.08)	0.22***	−0.03	0.20***	0.03	−0.12***	0.13***	−0.20***	−0.12***	0.07***	–

^a0 = Female, 1 = Male.

^b0 = No, 1 = Yes.

** p < 0.01, *** p < 0.001.