Table 6.

Analysis of the effects of demographic, lifestyle, and work factors on WASO

		Adjusted
		OR	95% CI			p
Age		1.00	0.98	–	1.02	0.93
Sex	(Ref: Male)	0.42	0.29	–	0.61	<0.01
Body mass index		1.05	0.99	–	1.10	0.08
Lifestyle habit
Longer sleeping hours on weekends than on weekdays	(Ref: No)	0.71	0.50	–	0.99	0.05
Nightcap	(Ref: No)	1.23	0.85	–	1.79	0.28
Smoking	(Ref: Former and never)	1.37	0.75	–	2.52	0.31
Exercise habits	(Ref: Once a week or less)	1.11	0.73	–	1.70	0.62
Smartphone use at bedtime	(Ref: No)	1.82	1.25	–	2.67	<0.01
TV watching in the bedroom	(Ref: No)	1.08	0.75	–	1.54	0.68
Water ingestion at bedtime	(Ref: No)	1.89	1.20	–	2.98	<0.01
Ingestion of a caffeinated beverage
Coffee	(Ref: One cup per day or less)	0.97	0.68	–	1.39	0.87
Green tea	(Ref: One cup per day or less)	0.95	0.68	–	1.32	0.76
Tea	(Ref: One cup per day or less)	1.21	0.81	–	1.83	0.35
Energy drink	(Ref: One cup per day or less)	1.16	0.42	–	3.19	0.78
Shift worker	(Ref: No)	1.35	0.76	–	2.39	0.31
Commuting time (hours)		1.39	0.97	–	2.00	0.08
Brief Scale for Job Stress
Workload		0.76	0.58	–	1.00	0.05
Mental workload		1.35	1.01	–	1.79	0.04
Problems in personal relationships		1.04	0.81	–	1.32	0.77
Job control		0.75	0.58	–	0.97	0.03
Reward from work		1.33	1.05	–	1.68	0.02
Support from colleagues and superiors		0.88	0.66	–	1.18	0.40

Statistical analyses were conducted using binomial logistic regression.

OR: odds ratio

CI: confidence interval

WASO: wake time after sleep onset

Logistic regression analysis, n = 693.