Prevalence of attention-deficit/hyperactivity disorder symptoms and their associations with sleep schedules and sleep-related problems among preschoolers in mainland China

Table 3 Crude and Adjusted odds ratios for the relationships between sleep and ADHD symptoms among preschoolers

Sleep schedules and sleep-related problems	High ADHD symptoms
Sleep schedules and sleep-related problems	Crude OR (95% CI)	P	Adjusted^aOR (95% CI)	P
Bedtime on weekday
Before 9:00 PM	1.00		1.00
Between 9:00 and 10:00 PM	1.21 (1.06 ~ 1.37)	0.003	1.36 (1.19 ~ 1.54)	< 0.001
After 10:00 PM	2.29 (1.92 ~ 2.74)	<0.001	2.50 (2.09 ~ 3.00)	< 0.001
Bedtime on weekend
Before 9:00 PM	1.00		1.00
Between 9:00 and 10:00 PM	1.18 (1.02 ~ 1.37)	0.029	1.36 (1.17 ~ 1.58)	< 0.001
After 10:00 PM	1.76 (1.49 ~ 2.07)	<0.001	2.04 (1.72 ~ 2.42)	<0.001
Time falling asleep
≤ 15 min	1.00		1.00
16~ 30 min	1.19 (1.01 ~ 1.41)	0.042	1.15 (0.97 ~ 1.37)	0.097
≥ 31 min	1.87 (1.56 ~ 2.24)	<0.001	1.76 (1.47 ~ 2.11)	< 0.001
Sleep duration
≤ 8.5 h	1.00		1.00
8.6~ 9.4 h	0.76 (0.66 ~ 0.86)	<0.001	0.76 (0.67 ~ 0.87)	< 0.001
≥ 9.5 h	0.76 (0.65 ~ 0.88)	<0.001	0.72 (0.62 ~ 0.84)	< 0.001
Having naps
Often	1.00		1.00
Occasionally	1.23 (1.07 ~ 1.40)	0.003	1.19 (1.04 ~ 1.36)	0.013
No	1.54 (1.32 ~ 1.80)	<0.001	1.57 (1.34 ~ 1.84)	< 0.001
Having sleep-related problems
No	1.00		1.00
Occasionally	1.91 (1.60~ 2.26)	<0.001	1.91 (1.60~ 2.26)	<0.001
Often	4.48 (3.79~ 5.30)	<0.001	4.57 (3.86~ 5.41)	<0.001

^aAdjusted for age, gender, household registration, parental age and education level, self-reported monthly household income per capita, TV viewing on weekday and weekend, outdoor activities