Table 2.

Univariate analysis of the duration of electronic media device usage with sleep quality (PSQI^a global score).

Duration of device usage			Total (n)		PSQI global scores, mean (SD)		P value
Televisionb						<.001
	Nonuser	308		5.05 (2.88)
	<1.5 h	394		4.91 (2.79)
	1.5-2.5 h	345		4.37 (2.53)
	2.5-3 h	213		4.42 (2.96)
	>3 h	160		5.13 (2.89)
Computerc						.009
	Nonuser	685		5.02 (2.91)
	<2 h	427		4.70 (2.69)
	2-4 h	164		4.25 (2.66)
	>4 h	143		4.64 (2.60)
Mobile phoned						.27
	Nonuser	202		4.88 (2.82)
	<2 h	552		4.81 (2.74)
	2-4 h	365		4.57 (2.80)
	>4 h	305		4.98 (2.87)

^aPSQI: Pittsburgh Sleep Quality Index.

^bNo linear association; P=.58; quadratic: P=.003.

^cNo linear association; P=.05; quadratic: P<.001.

^dNo linear association; P=.52; not quadratic: P=.12.