Table 4.

The association between smartphone use characteristics and smartphone addiction, using crude and multivariable logistic regression.

Variables	Not addicted n (%)	Smartphone addicted n (%)	Crude OR (95%CI)	p-value	Adjusted OR (95%CI)	p-value
Total hours spent on phone per day
≤ 2	165 (79.7)	42 (20.3)	0.55 (0.36–0.85)	0.007**	0.61 (0.39–0.96)	0.031*
3	169 (68.4)	78 (31.6)	Ref.	-	Ref.	-
4	123 (54.4)	103 (45.6)	1.81 (1.25–2.64)	0.002**	1.75 (1.19–2.57)	0.005**
5	88 (54.3)	74 (45.7)	1.82 (1.21–2.74)	0.004**	1.67 (1.09–2.57)	0.019*
>5	89 (46.1)	104 (53.9)	2.53 (1.71–3.74)	<0.001**	2.45 (1.63–3.69)	<0.001**
Latest time on phone
Before 11 p.m.	98 (80.3)	24 (19.7)	Ref.	-	Ref.	-
11:00	78 (76.5)	24 (23.5)	1.26 (0.66–2.38)	0.484	1.14 (0.58–2.24)	0.697
11:30	92 (68.7)	42 (31.3)	1.86 (1.05–3.32)	0.034*	1.82 (1.00–3.32)	0.049*
12:00	99 (58.9)	69 (41.1)	2.85 (1.66–4.89)	<0.001**	2.51 (1.42–4.43)	0.002**
12:30	74 (54.4)	62 (45.6)	3.42 (1.96–5.99)	<0.001**	3.29 (1.83–5.90)	<0.001**
1 a.m. or later	177 (50.1)	176 (49.9)	4.06 (2.48–6.65)	<0.001**	3.91 (2.32–6.61)	<0.001**
Time between latest phone use and bed time
1 h or more	64 (76.2)	20 (23.8)	Ref.	-	Ref.	-
30 min−1 h	103 (68.2)	48 (31.8)	1.49 (0.81–2.74)	0.198	1.47 (0.78–2.76)	0.230
<30 min	451 (58.0)	327 (42.0)	2.32 (1.38–3.91)	0.002**	2.17 (1.27–3.70)	0.004**

Crude Odds Ratio (OR) and adjusted ORs. OR, odds ratio; CI, confidence interval; SAS-SV, Smartphone Addiction Scale–Short Version.

^*p <0.05;

^**p <0.01.

Adjusted for age, gender, ethnicity, and recruitment site. For total hours per day, model fit with the adjusted Chi-squared = 77.801, p <0.001. For latest time on phone, model fit with the adjusted Chi-squared = 78.502, p <0.001. For time between latest phone use and bed time, model fit with the adjusted Chi-squared, 43.977, p <0.001.