Table 6.

The association between use of mobile phones after lights out and sleep disturbances among Japanese adolescents: Excessive daytime sleepiness and insomnia symptoms

Number of times mobile phones used after lights out, based on type of use		Excessive Daytime Sleepiness						Insomnia Symptom
		Crude			Adjusted			Crude			Adjusted
	N	OR	95% CI	P value	OR	95% CI	P value	OR	95% CI	P value	OR	95% CI	P value
For calling				< 0.01			< 0.01			< 0.01			< 0.01
0	67646	1.00			1.00			1.00			1.00
1-3/mo	6229	1.45	1.38–1.53		0.98	0.92–1.04		1.46	1.38–1.55		1.13	1.06–1.21
1/wk	4423	1.30	1.22–1.38		0.91	0.85–0.98		1.50	1.40–1.61		1.19	1.10–1.29
Several/wk	7441	1.58	1.50–1.65		0.98	0.93–1.04		1.79	1.70–1.89		1.26	1.18–1.34
Daily	7853	2.12	2.02–2.22		1.17	1.10–1.24		2.47	2.35–2.60		1.44	1.35–1.53
For sending text messages			< 0.01			< 0.01			< 0.01			< 0.01
0	50349	1.00			1.00			1.00			1.00
1-3/mo	6204	1.40	1.32–1.47		1.24	1.17–1.31		1.15	1.08–1.23		1.07	0.99–1.15
1/wk	5767	1.39	1.32–1.47		1.16	1.09–1.23		1.20	1.12–1.28		1.02	0.95–1.10
Several/wk	14698	1.74	1.68–1.80		1.37	1.31–1.43		1.43	1.37–1.49		1.12	1.07–1.18
Daily	16696	2.28	2.20–2.36		1.50	1.43–1.57		2.28	2.19–2.37		1.45	1.38–1.53

OR, odds ratio; CI, confidence interval.

^aAdjusted factors include sex, grade, drinking alcohol, smoking, eating breakfast, extracurricular activities, and mental health.

^bSubjects with missing date were excluded from the analysis.